The device of the roof of a private house - the main elements and features of various types of roofing. Types and schemes of truss systems: an overview and recommendations for the installation of a roof truss system
December 12, 2017Specialization: facade finishing, interior finishing, construction of dachas, garages. The experience of an amateur gardener and horticulturist. He also has experience repairing cars and motorcycles. Hobbies: playing the guitar and much more, for which there is not enough time :)
Any roof is subjected to various loads every day, as it is affected by wind, precipitation, and it also holds the roofing. In order for the roof to cope with all these loads for many decades, it must be properly designed. Therefore, for everyone who wants to do construction on their own, I recommend to figure out what parts and nodes of the truss system exist, and what function they perform.
Frame elements
All details of truss systems can be conditionally divided into two types:
- Basic. These parts form the roof frame, called the truss system. Not a single roof can do without them;
- Additional. This group includes elements that may be present in some types of roofs, while others do without them. The task of additional elements is to increase the rigidity and strength of the frame.
Main knots
So, the following elements belong to the main nodes and details of the truss system:
- Mauerlat. This, one might say, is the basis of all roofing systems, since rafter legs rest on the Mauerlat. Its design is extremely simple, in fact, it is an ordinary bar (a log in log houses), laid along the perimeter of the walls. Its task is to evenly distribute the load from the roof to the walls of the building.
It must be said that at a gable roof, the Mauerlat can be located not along the perimeter, but only on the side walls, since pediments are located on the end walls, which are a continuation of the wall;
- Rafter legs (hereinafter CH), or simply rafters. These parts are the supporting element that forms the slope and its angle of inclination. They take on the wind and snow load, as well as the weight of the roofing material, and transfer it to the walls through the Mauerlat and other elements.
Rafters are lateral (main), diagonal (installed at the junction of hip roof slopes) and shortened (diagonal rafters rely on Mauerlat);
- Rafter farms. They are formed by paired (reciprocal) rafter legs. It must be said that truss trusses are present on all pitched roofs except for shed roofs, since they do not have reciprocal rafters;
- Skate knot. It is the top of the roof truss, i.e. formed by the junction of two CHs. The ridge knot, like the trusses themselves, is absent only from shed roofs.
That's all the main knots of wooden roof structures that form them.
Additional
Additional details include:
- Run. This is a horizontal beam that connects all CHs within one slope;
- Skate run. It is the same horizontal beam as a regular run, but which runs in a ridge knot, i.e. connects two legs of each truss at the same time.
I must say that the ridge run can be installed in several ways - above the junction of the rafters, in the center of the junction, i.e. legs rest on the run, or under the rafters;
- Puff (bolt, fight). It is a beam that connects two reciprocal legs, preventing them from moving apart. We can say that the tightening removes the spacer load from the bearing walls;
- Supports. Can support rafters, all types of runs or puffs. Supports transfer the load to the internal walls of the building, columns or ceilings;
- Struts (rafter legs). They are inclined supports, which have the same function as the vertical racks. The only thing is that they support only the legs, i.e. are one of the elements of wooden trusses. Rafter legs transfer the load to the load-bearing elements of the building, or to the ceiling;
- Filly. These elements form the overhang of the slope in the event that the CHs do not go beyond the walls. In fact, they lengthen CH, i.e. are their continuation.
That's all the elements that make up the frames of pitched roofs.
A few words about the types of systems
So, we figured out the nodes, now let's look at the main types of truss structures. There are several of them:
- Shed. As I said, these structures do not have trusses. The angle of the slope is formed due to the different heights of the walls on which the CHs are laid, or due to the run, which is laid on racks installed on one of the walls;
- Gablesloping. Rafters are called rafters, which are supported by racks or struts that transfer the load to the internal load-bearing elements of the building. The frame of such structures is formed only by trusses, i.e. they do not have diagonal legs.
- gable hanging. Hanging rafters differ from layered rafters in that they transfer the entire load from the roof only to the outer walls;
- Hip. Unlike gables, at the ends instead of vertical gables they have inclined hips, i.e. end slopes. As I said, the hips form diagonal and short legs;
- broken lines. They are a gable structure, each CH of which is divided into two parts and is located at a different angle. Skating, i.e. the upper legs form a gentle slope, and the lower legs are steep. This design allows you to increase the attic space, as a result of which it can be used as an additional floor.
Typical broken (mansard) systems have racks on which the upper and lower CHs rest. The reciprocal racks are interconnected by puffs (attic floor beams).
There are also semi-mansard structures, which, in fact, are ordinary hanging gable roof systems. The only thing is that their fastening with a Mauerlat is usually made sliding (movable), which allows you to increase the CH deflection, and thereby reduce the spacer load on the walls.
Despite the fact that the designs of all the above systems are different, they consist of the same parts that we have already familiarized ourselves with.
One last thing about fasteners
Finally, I propose to consider how the connections of the main nodes are made, such as:
- Rafter / Mauerlat;
- Skate knot.
The rest of the details do not deserve special attention, since their docking most often occurs by washing down the interface (to increase the area of \u200b\u200bfitting the parts) and lining the steel plastic / corners, which are fixed with screws. Sometimes fasteners are not even used, i.e. parts are fastened to each other with screws without any overlays.
Connection of rafters and Mauerlat
The leg and Mauerlat mount can be made in several ways:
- With grooves. In this case, grooves are cut out under the Mauerlat, into which CH is inserted. Then it is additionally attached to the Mauerlat on both sides with a steel corner;
- Tooth and thorn. This method is usually used to attach the CH to the puff. Its principle is based on the fact that a spike is selected at the end of the sawed CH, and a groove is selected in the puff. In addition, the leg itself rests against the so-called tooth, i.e. protrusion in the puff, which takes on the expansion load.
It must be said that in recent times, fasteners such as a tooth with a spike are rarely used, since it is much easier to use special fasteners, the same corners and plates;
- By washing down. In this case, the CH is sawn so that a right angle is formed at the junction with the Mauerlat, as a result of which the rafter not only rests on the beam, but also rests against its side surface, thus transferring the spacer load. I must say that instead of washing down, you can fix the bar, as shown in the diagram below.
Connection of rafters and ridge run
The connection of CH and run can be done as follows:
- With a groove. In CH, two reciprocal cuts are made, as a result of which, after the junction of the rafters, a groove is formed for the ridge run;
- Hard pinching. The principle is based on the fact that puffs are installed under the run and above it;
- Got drunk on the way. This is the simplest and most common method, the principle of which is based on sawing CH for maximum fit to the beam. In this case, fixation is carried out with a steel corner.
Here, perhaps, are all the main nuances of assembling truss systems.
Conclusion
We have found out what parts the truss systems consist of, what types they are and how their main elements are connected. If I missed some points or something is not clear to you - write comments, and I will be happy to answer your questions.
December 12, 2017If you want to express gratitude, add a clarification or objection, ask the author something - add a comment or say thanks!
The positive effect of wood has always been appreciated by people, which is why we are still seeing the use of this material both for the installation of walls and for the construction of roof structures. Wooden houses are beautiful, practical and comfortable. The final stage of construction of any building is the roof, so keep in mind how a wooden roof is created by hands and how long it will take.
Wood, the first material used in the construction of residential buildings, is becoming popular with modern craftsmen. A few decades ago, the cost of such a roof was the lowest, and the installation was the easiest. Now things are different: the material is very expensive and it takes a lot of technical training and experience to place it.
As before, a wooden roof with all the rules will allow you to get an exclusive design that will last for many years.
Description of wooden roof installation
Depending on the selected materials, the installation technique and the roof mast are determined.
The hardest part will probably be working with the cup. If the builder is inexperienced with these types of parts, then a wooden roof by hand may cause some problems or not work at all.
Outside the material are small plates (width - 10-15 cm, length - 40-70 cm), which are chopped manually or by hand. Due to the roughness formed in the cut, moisture is absorbed, so the material is of great importance with the presence of natural fibers.
On one longitudinal side, the plate is cut until the thickness reaches 3-5 mm, and on the other side, a wedge groove is cut with a depth of 10-12 mm, as shown in the figure. The gon consists of coniferous, brick and oak. A box (rod or rod with part 40×40 mm or 50×50 mm) is used as the basis for laying the lid. Wood roof calculation is done by fixing a shaft or rods with a shaft length of 1/3 inch and solid foil can be formed from the panels.
Horizontal types of materials are arranged in accordance with one direction of the gutters and fix the narrow ends of the tiles in them. Once the slabs are level on the roof, they are squashed with the top edge against the wood. Nails must be inserted into the box at least 20 mm. The choice of nail depends on the type of wood, so cedar and larch are fixed with brass, while other types of wood can be fixed with galvanized nails.
How reliable a wooden roofing device is depends on the layer of pebbles:
- For pavilions and commercial buildings, layers are enough where the new line is located, covering half of the previous panel (see "How to make wood tiles, the roof of the device").
- The construction of residential buildings is carried out on the basis of three layers, and the new line is on top of the previous one.
- Buildings requiring high quality and reliability may contain a four-layer structure, with new rows located on top of the previous ¾.
When laying, the upper slabs are located at the bottom to the middle of the previous row.
The patchwork definition (roof connections with a concave end) acts like a fan, which, the narrow sides of the panel, is cut down defined, so that the tiles become trapezoidal.
Before building a wooden roof, all parts are pre-treated with antiseptic agents, and fire-fighting use a fire-resistant compound. Also read: "Device on the roof of the house."
The installation of proportions and filmmaking is carried out similarly to a cup. Since the boards are short (about 20-40 cm), the distance between the glow beams decreases. The elements do not have common grooves, so they fit into the connection at the joint, taking into account that the wood can rotate over time (with a distance of 3-5 mm between the plates).
In wet weather, the joints of the wooden structures of the roof will exactly match each other, and in warm weather they will create optimal conditions for the ventilation of the wood.
The construction of a wooden roof is in most cases larch, which is distinguished by:
- high density and resin content, corrosion and insect protection;
- the duration of the operation;
- attractive wood structure;
- low price.
Characteristics of wood chip and tile roofing
Such material is embedded in three or four layers that overlap both vertically and horizontally.
A length of shingle is attached to a wooden roof - its patterns are not much different from other types of structures, like shingles. Neighbors should be closed up to 25-30 mm.
The new horizontal layer must be installed in such a way that the joints of the two lower belts are covered by one of the upper ones. Each shield to wear the nail shield struck 70×1.5mm, followed by the stitching of the wooden corner comb.
The construction of slate roofing follows the same technology as shortened planks.
Usually they are offered in lengths from 40 cm to 10 m, width 9-13 cm, thickness 3-5 mm. The dimensions of the chips are somewhat smaller: length - 40-50 cm, width - 7-12 cm, thickness - 3 mm. Of these features, the chips are attached to the box in increments of about 15 cm, the holder - from 30 cm. Both materials are very light, so they should be at least 40 x 40 mm.
Roof covering - various options, see video:
Roof features
If a do-it-yourself wooden roof is to be built, this will be the easiest and most affordable option for many just above the roof.
However, this coating will serve to reduce the order, as a result of the destruction of the natural structure of the wood when sawing. If you want to preserve the properties of the field, you must prepare slabs separating the logs in length, that is, in the same direction as the fibers of the material. Such coating will be carried out with due care for at least a hundred years.
When building the roof of a wooden house, there are two ways of laying theses: transverse and longitudinal. The cross-section method is the simplest wooden roof device, but it is only suitable for temporary construction.
Nail plates, like any other coating, from the bottom up with a 5 cm coating of the bottom row of the top.
The difference in the longitudinal method has several styling options:
- in the form of a two-layer coating - the plates are fixed with the top layer, which moves to the lower part to the middle of the plate, and for swelling it remains 0.5 cm;
- in the first row, the plates are spaced at 50 mm intervals, the elements on the next row must be covered up to 50 mm from each previous plate;
- when using a latch - the bottom line is solid, you must use narrow strips to cover the joints, which should be 50 mm.
Regardless of the method that restores wooden roofs, to ensure that the top nail is securely attached to each row on the slab in increments of 600-800 mm in thickness from 19 to 25 mm, the cross section of the beam is 60x60 mm.
Before choosing a material, read: "How to choose a roof for a house."
1. Description of the roofing materials used
2. What elements does the roof consist of
3. Features of load-bearing structures
During the construction of wooden houses, the task is to rationally combine the aesthetics and practicality of the roof structure.
Among the large selection of materials, far from everything is suitable here, which significantly complicates the construction technology.
Following the main requirement, it is necessary to pay attention to ensuring that the roof structure of a wooden house looks harmoniously against the background of the entire building. Wooden houses have always been in great demand among connoisseurs of environmentally friendly and natural materials, and the correct processing of the log allows you to achieve good thermal insulation, ease of installation and reliable fastening of suspended structures.
A significant disadvantage of wood is its deformation during temperature fluctuations, especially changes in humidity levels, which must be taken into account when choosing one or another lumber.
Particular attention is paid to the order of assembly of window and door openings, shutter speed for shrinkage of the log house. The problem areas include a wooden roof - its construction is being built according to certain rules (read: "The device of a wooden roof - features of the coating"). As already mentioned, a special material is selected for it, it is installed under certain conditions, during operation it requires increased control than, for example, when building a roof on a stone building.
The shrinkage coefficient of raw logs and timber is 10%, raw profiled timber reaches about 5%, dried and glued timber - up to 3%. Based on these values, two values are noted in the construction project of wooden houses - before the material has sat down, and after that.
As a rule, the roofs of such houses are pitched, which is indicated even in the snip - wooden roof structures are flat and shed are considered impractical and outwardly unattractive.
A large selection of pitched configurations allows you to choose what the future home owner likes, for example:
A pitched roof has a number of advantages over other types of roofs:
- has the best thermal insulation of wooden floor trusses;
- under it you can equip the attic;
- cheaper roofing is suitable for it;
- snow masses descend from the roof as they accumulate;
- rainwater rolls off faster;
- you can make long roof overhangs, so that precipitation will be removed far from the walls.
Description of the roofing materials used
The construction or reconstruction of the roof of a wooden house is being carried out using any of these coatings:
- built-up materials on bituminous mastic, for example, euro tiles;
- rolled deposited materials;
- ceramic and metal tiles;
- slate;
- ondulin.
The use of euroslate and corrugated board for wooden houses will lead to noise from the rain, and due to the reduced waterproofing properties, constant repair of the roofing pie will be required.
Rafter system nodes - how to make a reliable roof?
The exotic option includes the arrangement of the roof in the form of a longitudinal overlap of the edged board, or "historical" materials (thatched roofs, reeds). However, the so-called wooden roof, the design of which practically does not differ from traditional options, will be relevant in the locations of eco- or ethno-villages close to nature. See also: “Reed roof”.
What elements does the roof consist of?
The roof is assembled from several interconnected components, pictured :
- Slopes - inclined roof surfaces, which can be flat or curved.
- Ridge - the upper longitudinal rib at the junction of the slopes.
- The ribs of the slope, represented as a protruding corner at the intersection of the slopes.
- Endova, also called a groove, which is a concave intersection of slopes.
- Eaves overhang - a slight protrusion of the roof beyond the frame (at the final stage, we hem the roof eaves with a finishing material).
- Gable overhang - part of the roof, hanging over the wall.
- Gutter.
- Downpipe.
- Chimney.
Regardless of the choice of roof covering, the structure of the roofing cake must be completely preserved.
For the crate are taken: for metal materials and slate - bars or boards, for tiles only boards.
If materials on bituminous mastic are used, then the crate is laid in a continuous sheet. In the case of using an attic or attic for living, interior decoration is also performed. But in any case, the order of laying the layers of the cake must be observed.
So, if the owner of the house independently builds wooden roof structures, then you need to adhere to the basic requirements:
The truss system of a wooden house, in detail on the video:
Features of load-bearing structures
Before the construction or reconstruction of wooden roofs begins, a scheme for its construction is carefully selected. The pitched roof is fastened to certain rafters. The most common are the layered and hanging structures, which differ only in that in the first version there is an intermediate support, or a support for an internal load-bearing wall or partition.
The support should not be located further than 6.5 m from the outer wall, and the second support helps to increase each run - the distance from the middle support beam and the outer wall is up to 15 m. Mauerlat (rafter beam) in a wooden house is constructed from the upper wall row of logs .
Hanging rafters are supported only by walls subjected to bursting force.
For beginners who have no idea about such installation, it is better to order a finished house project from a special company. Typical and universal designs of wooden roofs will be offered there, and an individual option can be developed (read: “The device of the roof of a wooden house: which roof to choose”).
If raw lumber is used in construction, then it is important to let the building settle, while the arrangement of the node should be with special “sliding” elements.
As soon as the shrinkage of the rafters begins across the location of the beam, then with the help of such a wooden roof device it will be possible to maintain their longitudinal binding.
By analogy with this, the rafters are also fastened next to the ridge.
The result of such actions will be that even with significant shrinkage, the wooden roof structures will remain in their original place and will not deform.
Summing up, one should pay attention to the rather complex structure of wooden houses, the design and installation of which requires high professionalism. Beginners who do not have certain skills cannot cope with the work themselves. As for the choice of materials, varieties of roofs, everything is limited only by the budget of the owner of the house.
Read also the article: "Plate roofs - a device."
Do-it-yourself hip roof: the construction process
The roof shed is ready.
Wooden roof - ecology, economy and reliability
It's time to make the roof truss system. Consider the step by step process of its installation.
Consider the process of erecting and installing a hip roof (four-pitched roof), which consists of corner, intermediate and auxiliary rafters. The work is not very difficult, it can be handled by a person without experience. The main thing is to make the right calculations.
The construction of the hip roof begins with the laying of the Mauerlat, but since we have a log cabin under the roof, the upper log will serve as the Mauerlat.
Laying floor beams
So, it's time to mount intermediate floor beams, with a section of 10 by 20 centimeters and an intermediate step of 0.5-0.6 meters (there may be other values).
Attaching them to the beam will not be difficult.
It is enough to lay the bars on top of the logs and fix them with metal corners.
It is possible to make cuttings in logs. To do this, you first need to make an accurate marking of future holes, then take a chainsaw with a sharp chain and make cuts with a depth equal to half the log section.
The height of the grooves should be 3 centimeters higher than the height of the beams in order to align them if necessary.
When the cuts are made, armed with a chisel and a hammer, you need to bring the matter to mind, giving the holes the desired shape.
Be sure to check the horizontal beams by level.
Before laying the beams, their ends must be wrapped with pieces of eurofoam (insulation) soaked in an antiseptic solution, then additionally fix the beams with metal squares.
Installation of the skate
First you need to do the markup.
To do this, divide the gable walls in half (take the dimensions as accurately as possible).
Set aside the resulting size (from the center to the extreme wall) on the wall perpendicular to the gable, on both sides.
Similarly, repeat the procedure on the opposite side of the hip roof.
The distance between the lines will be equal to the length of the skate, the racks of which are installed at the intersection of the "squares".
Rack installation
For vertical racks we will use boards with a section of 5 by 15 centimeters, for a ridge - 5 by 20 cm.
Racks are set strictly vertically and supported by temporary braces on both sides.
Attached with self-tapping screws.
There should be two boards in one rack.
Between the vertical posts (between two boards of one vertical post) a ridge beam is installed and fastened with bolts. Additionally, a spacer can be mounted between the vertical posts.
Rafter installation
Rafters must be mounted on the installed ridge run. For this purpose, boards with a section of 5 by 15 centimeters are used (you may have others, depending on the calculations).
They are laid in increments of half a meter on the ridge run from both sides with an overlap. Then the boards are carefully cut at the top with a saw so that they can be joined end-to-end. The rafter legs are joined with metal profiles and self-tapping screws.
In the lower part of the hip roof, the rafters are installed on the mauerlat by cutting, which is done at an angle of 90 degrees.
It rests on the upper log and is attached to it with metal corners using self-tapping screws or nails.
You can also make small grooves on the log, insert the rafter legs into them and fix them in the same way.
The length of the boards should be such that the overhang over the eaves is at least 30 centimeters.
This is how all ridge rafter legs are installed.
After the installation is completed, the installation of the corner rafters begins.
Installation of corner rafters
The corner rafters are mounted first, which run along the center of the pediment. The section can be left the same.
Their length can be calculated using the Pythagorean theorem.
But you can simply place a temporary board between the ridge and the center of the gable wall beam and measure it.
Then add from 30 to 50 centimeters to the resulting value, which will “go for take-away”.
On the board, you need to prepare another one, on the opposite side, and then fix both to the ridge and the Mauerlat below. Boards are attached to the Mauerlat by cutting down.
Similarly, rafters are prepared and mounted on the four corners of the hip roof of the log house with their own hands.
Under all rafter legs, racks must be installed near the Mauerlat.
Installation of intermediate rafters
It remains only to install intermediate rafters.
To do this, the walls are marked with the selected step so that there is always a right angle between the marks on adjacent walls. At the intersection of two lines, a mark is made on the corner rafter.
Next, all distances are measured, rafter legs of the required length are prepared, taking into account the eaves overhang, and they are installed.
To attach the intermediate rafters of a floating roof for a log house to the corner ones, their ends must be cut at an angle of 45 degrees and fastened with bolts.
To simplify the calculations, it is possible to nail a board between the corner rafter legs and “dance” from it.
If the length of the boards is not enough, they can be spliced in various ways.
When all the rafters are installed, it is necessary to mount cornice boards around the perimeter of the hip roof, and then proceed with laying the battens and roofing material.
The type of lathing for the hip roof of a log house depends on what roofing material is planned to be used.
If soft roofing materials are used, for example, shingles, then the base must be solid.
Under hard materials, a sparse crate is made.
The step of the lathing also varies depending on the material for the roof.
The required pitch value is usually indicated by the manufacturer of the roofing material.
When installing a roofing pie, it is imperative to use insulation, vapor and waterproofing. You can read about how to install a certain type of roofing on our website in the relevant articles. The sequence of work is detailed there. To simplify the calculation of hip roof elements, you can use programs.
Hip roof, truss system
Terms used in the construction of wood veneers
- The rafter is the load-bearing part of the roof, which includes multilayer supports, buttresses and vertical columns supported by Mauerlat.
- Skobel is part of the gorge.
- Mauerlat, presented as a support for several rafters, or in other words, on a bar placed at the top of the wall, evenly distributes them to the roof load, it is important to understand why you need a mauerdat.
- Tightening - A rail that is horizontally positioned to connect roof tiles and reduce horizontal impact on them to ensure stability on the roof, also used as a holder.
- Headstock - strengthens the scissors, sets: the lower part - is tightened; up - as support for the rafters.
- The spacer is attached as a connecting element between the logs.
- The hanger is in the form of an inclined beam, which is used to support the beams of wood that are adjacent to the horizontal parts (columns and pillars).
- The horse is horizontally mounted on the roof of the raid.
During the construction of wooden roof hinges can be divided into several groups:
- connecting legs with Mauerlat;
- connecting legs and elements of a wooden base for the roof, which makes the structure more solid and durable;
- A knot with flat parts is connected by stretching out from it.
Depending on the desired result, the rafters are connected to the Mauerlat with a rigid or sliding knot.
It should be noted that in some cases a rigid installation can even destroy the structure, as in the picture, since the weather conditions are favorable for pressing and opening the wood, but due to the rigid connection of the nasson system, it can deform the bearings of the wall under heavy load.
Features of hard knots
A solid wood roof assembly has the following shape:
- The cutting is done at a depth of one third of the panel on the shoulder of the shoulder.
The machines should then be attached to the Mauerlat with nails so that two of them hit at a slight angle on the side of the rafters and one hits in the vertical direction.
- For a 1 m rafter, the lifting timber is put in place as a support for the mauerlat, the side fixing screws are screwed in with metal corners in this position.
Characteristics of sliding knots
The connection of the elements of the nasal system is carried out using sliding knots.
The use of suspended rafters is useful in round timber roof construction where the spine pole is used as a support for the rafters and there is no spacing between loadbearing walls.
Newly built wooden farmland will be saved within a few years, so using rigid fixtures to permanently move the truss will cause the walls to warp.
To avoid such problems, wooden roofs are scissor system components that must be determined with a free movement permit, built as follows.
The curved leg, using a pre-made saw, rests on the Mauerlat and is tied (two on each side, the third vertical).
- Metal tiles dropped from the wall are attached to metal corners that connect them to the mauerlat.
- Metal structures are determined by the "trace" method (see "Metal Truss, Cons and Advantages").
- Support of the foot in the Mauerlat should be carried out taking into account the movement of these systems in relation to each other.
- Roofs are not damaged in the event of a gale, the binding of struts, shepherds and spacers to the hanging rafters is done with clamps and clamps; there are also twisted wire rolls around the leg.
How to connect round legs
If the roof tension is large enough, special attention should be paid to the wooden roof hinges, as well as the columns, which will need to be expanded to the desired dimensions using one of the suggested methods.
How to connect pile rafters in construction
The developers pay special attention to the comb top connection mode.
The main findings of the scissor system, detailed in the video:
The difference between teeth and "tip"
- Due to its high strength, the spike connection is excellent for wooden construction.
The tip is the part that attaches to the journal, which connects to the socket, tongue, or ear of the second diary. The size and shape of these two elements must match each other.
- The tooth is connected to the stepped cut one day and the inscriptions the next. As in the case of the previous method, for a snug fit of wooden roof structures, the ratio of their size and shape must be taken into account.
If the developer is building a wooden roof, when connected to the roof elements, the knitting legs must be secured with screws, screws, clips and screws.
The diameter of the hole should be 1 to 2 mm of fasteners, and the brackets are fixed on both sides.
When using a screw connection on the scissors, a screw located at the top of the structure is used and the groove is cut at half the thickness of the log.
Only if these requirements are met will the journals closely coordinate with each other. In the next step, the assembly is attached to the screws and special brackets.
A flat roof can be avoided evenly - the nodes can be of any shape, with the same scissors. Experienced builders recommend template design so that all frames and cuts are the same size (see: "Building a Wooden Roof - Cap Specifications").
The description of the entire roof construction system is provided by the most complete presentation, but the wooden cart, which is quite difficult for beginners, requires a professional approach. Also read: "Building the roof of a wooden house: which roof should you choose."
In order for the constructed building to serve for more than one year, it needs both a reliable foundation and a strong roof system that resists the vicissitudes of the weather. The roof must withstand heavy loads with dignity: heavy snowfalls, sharp gusts of wind, torrential downpours. The roof truss system is best suited for this.
Roof trusses and its types
The truss system is the basis of the roof, which focuses on the load-bearing elements of the structure and also serves as a frame for various types of roofing materials: insulation, waterproofing, various coatings.
The dimensions and design of the rafters depend on:
- purchased material;
- the size of the building;
- dimensions of the house;
- building material for rafters;
- individual preferences of the customer;
- roof loads relevant for a particular region.
The rafter system has:
- crate - bars, in a perpendicular direction, fit on the rafter legs;
- screeds that perceive tensile forces;
- wooden racks, located in a vertical position;
- mauerlat - a bar, the installation of which is carried out along the wall, the rafters focus on it;
- rafter legs are a kind of wooden beams that take on the main load of the roof.
Each of these factors is very important, because it is necessary to understand what type of truss system will be best suited for a particular situation.
When it comes to low-rise buildings, wooden structures are the most common. In many cases, three types of truss trusses are used: hanging rafters, layered rafters and a mixed rafter system.
Characteristics of hanging rafters
Hanging rafters are the most elementary type of truss systems, their characteristics:
If the roof of the house is of complex construction, the types of rafters can be alternated. For example, in the presence of supports or the middle main wall, they install layered rafters, and in the absence of such elements, hanging rafters.
Features of layered rafters
For a layered rafter system, the house must be additionally equipped with a load-bearing wall located in the middle. There are layered rafters according to the following features:
The design of the combined system is the most complex, since it includes parts of two other types of rafters - hanging and layered. It is used for mansard roofing. The walls of the rooms, which are located on the second floor, form vertical supports, these supports are also intermediate racks for truss beams.
Part of the rafters that connect one end of the uprights functions as a crossbar for the slopes located on the side, and for the upper part of the structure they are a puff.
At the same time, the horizontal bars perform the following functions: for the upper slopes - a Mauerlat, for the side ones - a ridge beam. To increase the strength of the roof, struts are mounted that connect the side slopes and vertical racks.
The combined sling system is the most complex and time-consuming to manufacture, but these shortcomings are fully compensated by an increase in the bearing qualities of the roof in the absence of extra supports, especially when there is a need to cover significant spans in the building.
You can increase the bearing qualities of the roof using a mixed truss system
Rafter trusses for various types of roofs
During the construction of a certain building, roof systems of one kind or another are necessarily used, and the type of roof will completely depend on the design of the future building.
Rafter truss for a gable roof
A gable roof is a common roof construction for residential buildings that have no more than three floors. Preference is given to just such a design because of the technical characteristics of the inclined shape of the truss system, and also due to the fact that installation work is carried out easily and simply.
The truss system of a gable roof includes two rectangular inclined planes. The upper part of the building from the front side resembles a triangle. The main components of a gable roof are the Mauerlat and rafter legs. In order to properly distribute the load along the rafters and walls, struts, crossbars and racks are mounted, thanks to which you can create a durable, rigid, elementary and easy installation scheme for a gable roof structure.
A gable roof is considered the simplest roof system; it is used for residential buildings no more than three floors.
On top of the rafters, you can mount a sparse crate or a solid one, and then attach a bituminous coating, tiles or some other type of material to it. The rafters and sheathing itself are usually made of beams or boards, which are fastened with nails, bolts or metal fittings. Metal profiles can be used as rafters, due to which significant spans overlap. There is no need to use extra racks and struts.
The device of the truss system for a gable roof allows you to evenly distribute all the existing load along the perimeter of the building. The lower ends of the system focus on the Mauerlat. They are fixed with metal fasteners or staples. By the angle of inclination of the bars for the rafters, you can determine at what angle the roof slopes will be inclined.
The truss system for a gable roof allows you to evenly distribute the load from the roof along the perimeter of the building
Rafter system for a hip roof
When arranging a system for a hip roof, you will need to install different types of rafters:
- conjurers (shortened);
- side;
- hip main;
- sloping (diagonal elements that form a slope in the shape of a triangle).
The rafter legs located on the side are made of board, and they are mounted identically to the details of a traditional pitched roof with a layered or hanging structure. Hip main rafters are layered parts. For sprigs, boards or bars are used, which are attached not only to the Mauerlat, but also to the diagonal beams.
To install this type of construction, the angle of inclination is accurately calculated, as well as the cross section of the sloping beams. The dimensions of the parts also depend on the length of the span.
So that the hip roof does not deform from a heavy load, you should accurately calculate the angle of inclination of the diagonal beams for the rafters
Observe symmetry when installing diagonal beams for rafters, otherwise the roof is deformed from a significant load.
Rafter system for sloping roofs
A broken roof is a construction with rafters, which consist of several separate elements. Moreover, they should be located at different angles relative to the horizon. And since the lower rafter part is almost vertical, the attic of the building receives additional space, so that it can be used as a living space. The device of this type of roof is carried out during the construction of a four- or gable rafter structure.
Professionals need to calculate a four-pitched rafter system, but a gable broken roof can be made independently, since its installation is very simple. To do this, it is necessary to install a support frame, which should consist of runs, as well as racks. Horizontal parts are fixed with hanging rafters. But to the Mauerlat, the supports of the sloping roof are fixed with shortened legs of the rafters.
The assembly of rafters for a broken gable roof can also be performed by non-professionals, since the installation of such a roof is very simple.
"Cuckoo" in the roof truss
The so-called cuckoo on the roof is a small ledge that is located on the attic floor. Here is a window for better illumination of the attic room. The installation of the "cuckoo" is carried out carefully, while controlling the parameters of the entire structure: the depth of the cut, the angle of inclination and other factors. However, before that, the necessary measurements are made.
The first stage of work begins with the installation of a power plate (a beam with a section of 10x10 cm, which is needed to support the lines). The truss system acts as a skeleton for the roofing material. To stiffen the structure, spacers are used, which are mounted between the two legs of the rafters.
After the installation of the truss truss is completed, a sheathing is laid, the type of which depends on the roof covering purchased. The installation of the crate is done continuously or with a certain step. Boards, OSB and plywood sheets are usually used for it. In addition, the installation of roofing material must be identical throughout the entire roof.
The main difficulty in installing such a rafter system is the location of the internal corners. In these places, snow can accumulate, which means that the load will increase, which is why a continuous crate is made.
"Cuckoo" on the roof is called a small ledge on the attic floor, under which there is an additional window
Chalet roof truss truss
A feature of a device of this design is the removal of visors, as well as overhangs outside the house. In addition, there must be rafters and beams for the roof, which extend up to three meters on the sides of the building. Each of these elements is fixed with a bracket to the wall of the building in the lower part. Next, tie the edges of the beams. They serve as a support for covering the roof of the building.
But when creating large overhangs, it is necessary to install the reinforced belt in parallel with the installation of the Mauerlat studs. It is necessary to make anchors that help fix the consoles. In this case, the rafters will be perfectly fixed with anchors and, in addition, tie-ins.
To carry out the side cornices, a ridge beam is made, after which beams are taken out at the Mauerlat level, which must be identical to the length of the ridge. The truss is based on these structural details, and in the future - building material for the roof.
When designing a building, the angle of the roof-chalet is calculated based on the characteristics of the local climate and other factors. With a slope angle of about 45 °, the load from snow is not taken into account, since with this option it will not linger on the roof. At the same time, the sloping roof will withstand the load from the snow, but it is necessary to install a reinforced roof truss. Before installing the roof-chalet, a building project is prepared, because the originality of the roof itself, as well as long cornices and its overhangs, oblige this.
The roof in the style of a chalet is characterized by visors, taken out several meters outside the house.
Roof truss designed for soft roofing
Soft roofing is done in various ways, but there are common characteristics in the technological methods of its construction. Initially, you need to prepare. When equipping a roof for a house made of foam concrete or other material, a Mauerlat is first installed, then a cut is made under the ceiling beams in increments of up to one meter in the upper crowns of the building. The distance between the boards is calculated based on the type of rafter structure.
- Mount individual parts of the rafter system. To completely eliminate the risk, the boards of the rafter legs on the ground are attached with screws. After creating a truss truss, it is raised to the top of the building.
- All elements of the rafters are fixed with ceiling overlap, internal boards, jibs, and also crossbars. Further, this basis for the roof will become a single whole structure.
- The next stage is a crate, which is installed under a soft roof with small gaps or no gaps at all. Gaps of no more than 1 cm are allowed. Quite often, leveling plywood is installed on top of the boards. Its sheets are laid according to the brickwork method. The resulting joints do not align with the gaps between the plywood and the board.
If the length of the boards of the crates is not enough, then the joints of the parts must be located in different places. In this way, areas that have been weakened can be correctly distributed.
Self-manufacturing of the truss system
Before the installation of the truss system begins, the Mauerlat must be fixed to the longitudinal walls with anchors. Next, you need to decide on the desired section of the legs for the rafters, depending on the distance and their length. If there is a need to increase the length of the rafters, then connect them with various fasteners.
When using different insulation, you need to choose the ideal distance between the elements of the rafters in order to reduce the number of thermal insulation scraps.
Installation of the truss system must be carried out in the following order:
- A template is made according to which the farm is assembled. 2 boards are taken, corresponding to the length of the rafters, and connected to each other from only one edge with a nail.
A rafter template called "scissors" will help you quickly assemble the entire roof truss system
- You get a design called "scissors". Its free edges are placed on supports at the points of contact of the rafter legs. The result should be the final angle, that is, the angle at which the roof slope will be tilted. It is fixed with several long nails and transverse boards.
- A second template is made, thanks to which the cuts on the rafters are installed. It is made from plywood.
- Special mounting cuts are cut out on the rafters (a prepared template is used for this purpose) and connected at an angle of inclination of the slope. You should get a triangle that rises to the roof along the stairs. Next, it must be attached to the Mauerlat.
- Initially, two side gable rafters are mounted. Their correct installation in the vertical and horizontal plane occurs due to temporary struts attached to the rafters.
For the correct installation of the entire rafter system, the first pair of rafters is installed on the roof
- A cord is stretched between these tops of the rafters. It will indicate the future skate and the level of other rafters located in the gap.
- Raise and mount the remaining rafters at the initially calculated distance, which should be at least 60 cm from each other.
- If a bulky construction of rafters is provided, then it is additionally strengthened with struts, supports, and so on.
The bulky construction of the rafters is additionally reinforced with struts and supports.
- On special supports, a ridge beam is installed, to which not only short, but also diagonal and intermediate elements of the rafters are attached.
Proper fastening of the ridge beam ensures the reliability of the entire rafter system
Typical nodes of a standard truss system
The structural strength of the rafters depends on the ideally selected section of the boards, as well as on the high quality of the rafter units. The connection of parts for the roof structure is done in accordance with established rules.
The main typical nodes in the truss system:
- supporting knot of rafters on the Mauerlat;
- ridge;
- a node for combining the upper puffs and the entire truss system;
- fixing the strut, rack, as well as rafters and beams.
After the design of the rafter system has been chosen, it is necessary to draw up a plan in which to select all the nodes. In each design, they are made in different ways, since it depends on different nuances: the type of roof, its size, and the angle of inclination.
A rafter from a profile pipe is a metal structure that is assembled using lattice rods. The very production of such farms is a very time-consuming process, but also more economical. Paired material is used for the manufacture of rafters, and scarves are connecting elements. The construction of rafters from profile pipes is assembled on the ground, while riveting or welding is used.
Thanks to such systems, any spans are blocked, but it is necessary to make the correct calculation. Provided that all welding work will be done with high quality, in the future it remains only to transfer the structural elements to the top of the building and assemble them. Bearing rafters from a profile pipe have many advantages, such as:
Crossbar in the truss system
Rigel is a fairly broad concept, but in the case of roofs it has a certain meaning. The crossbar is a horizontal bar that connects the rafters. Such an element does not allow the roof to "burst". It is made of wood, reinforced concrete, and also metal - it all depends on the type of structure. And the crossbar serves to distribute the load exerted by the truss system.
It can be fixed in various places between the legs of the lines. There is a direct pattern here - if the crossbar is fixed higher, then the timber for its installation must be selected with a large cross section.
There are many ways to fix the crossbar to the truss system:
- bolts;
- nuts;
- studs with washers;
- special fasteners;
- nails;
- mixed fasteners, when different types of fasteners are used in parallel.
Mounting exists with a tie-in or overhead. In general, the crossbar is a design unit, as, indeed, the entire roof sling system.
The crossbar in the truss system is designed to reinforce the roof structure
Rafter system fastening
To ensure the reliability of the rafter system, it is necessary to initially find out how they are fastened to the supporting roof and the ridge. If fastening is done to prevent deformation of the roof during shrinkage of the house, then the rafters are fixed on top with a hinged plate or a nut with a bolt, and from below - with a sliding support.
Hanging rafters need a tighter and more reliable fastening in the ridge, so in this case you can apply:
- overhead metal or wooden plates;
- cutting method;
- connection with long nails.
In the layered system, the rafter legs are not connected to each other, since they are attached to the ridge run.
The rafters are fastened to the Mauerlat by cutting down, which is done in the rafter leg. Thanks to this method of fastening, the support of the roof will not be weakened. Cutting is also done when installing rafters on floor beams. In this case, the cut is also made in the support beam.
Video: how to make rafters with your own hands
Thus, a perfectly matched system of rafters and their structural characteristics will help create the basis for a reliable roof for your home.
The roof system is the outside part of the roof structure that is supported by the load-bearing structure. It includes a crate and a truss system. The triangle underlying this system should be a rigid and most economical structural element that contains the attachment points for the roof rafters.
The main characteristics of the nodes of the truss system
The main attachment points of the roof truss system are shown in fig. 1. They imply the presence of a rafter leg (Mauerlat - 1), a rafter leg (ridge run - 2), a rack (puffs - 3). The design of the truss system is the main load-bearing element of the roof.
All roof fasteners must be of sufficient strength to eliminate a significant degree of risk associated with roof collapse. The consequences of a mistake made when connecting elements can be the most unpredictable.
Figure 1. The main attachment points of the roof truss system: 1 - mauerlat, 2 - ridge run, 3 - puffs.
First, the rafters are installed on the Mauerlat if the building has brick walls. Similar nodes are provided for concrete blocks, then it is necessary to create a reinforced concrete stiffening belt, and it is necessary to insert studs into its design. Their location should be at a distance of 1 to 1.5 m from each other, and their diameter should be more than 14 mm. The top of the studs must be equipped with a special thread.
Mauerlat is drilled, making holes that are necessary for attaching elements to it. Each of the holes should be the same size as the diameter of the stud, and its pitch should correspond to the distance between the studs. A nut is put on each protruding end of the stud and tightened, which ensures the strength of the connection between the Mauerlat and the wall. The rafters should be connected to the Mauerlat in such a way that their bearing capacity is not weakened.
Description of the main fasteners for mounting the truss system
If during the construction of the house a rounded log or timber was used, then it is not necessary to create an armored belt. produced on the upper beam or on the log of the wall. For this purpose, connecting the Mauerlat with the rafters uses different methods of cutting (tie-ins).
What fasteners fasten metal rafters:
- Plates.
- Fasteners LK.
- corners.
- Brackets WW.
- Self-tapping screws.
- Varieties of the corner of the KR.
- Wire ties.
- Mounting tape perforated TM.
- Bolts with nuts.
- Brackets WW.
If brackets are used when connecting the rafters to the Mauerlat, then they are not cut into the rafters, which helps to strengthen the bearing capacity. Metal brackets are usually produced, and the metal is galvanized and has a thickness of 0.2 cm. The brackets are strengthened with nails, anchor bolts or screws.
You can use the LK fastener by creating attachment points not only for rafters with a Mauerlat, but also for various other elements that make up the roof structure. The LK fastener is fixed to the wood, as are the brackets, with the exception of the use of anchor types of bolts.
Mounting perforated tape allows you to strengthen the connecting nodes in the construction of roofing systems. It is used not only to create stronger nodes, but also to strengthen elements for additional use in order to give rigidity or strength to the system as a whole. They fix the perforated mounting tape with screws or nails, so it is used to strengthen the structure of the rafter system of any roof, the integrity of which will not be violated.
With the use of KR corners and their various modifications, the attachment points are reinforced so that they can effectively participate in the connection of the Mauerlat and rafters. Ensuring appropriate strength to the roof units is permissible when using corners, which improves the load-bearing characteristics of the roof structure.
The use of connecting elements made of metal is not associated with inserting corners into the roof system. This will not cause a decrease in the bearing capacity of the roofing system. You can use corners for connection using screws or nails, the protrusions of which resemble a ruff.
How are the knots connected in the ridge part?
There are three main types of fastening in the ridge parts of the roofing system:
- Butt connection.
- Mounting on the basis of a ridge run.
- Ridge joint overlap.
For the purpose of fastening, in the first way, the ridge part is cut off from the upper edge at an angle that is the same as the angle of the roof slope. Then it rests on the necessary rafter, which should also be cut at an angle, but on the opposite side of the roof. A special template is sometimes used to trim corners.
Nails for connecting the rafters under the ridge should be 150 mm or more in size, two of them will be needed. Each nail is driven into the rafters at the top of the rafters at the appropriate angle. The sharp end of the nail usually enters the cut of the rafter from opposite sides. Strengthening the ridge joint can be achieved by applying a metal plate to it on the side or a wooden lining so that it is enough to pull it with bolts or nails.
The connection in the second way, that is, through the ridge run, is associated with the strengthening of the rafters on the ridge beam. The run is one of the additional support beams or beams, which is a support for the rafters. It is located parallel to the ridge or Mauerlat. The method differs from the previous one in that a ridge beam is laid between the rafters, which are sawn at an angle, which is a laborious process, so this method is used less frequently.
A more common method is similar to the first, but it differs in that the fastening is overlapped, and the joint method is not used. The rafters should be in contact with the ends, and not the side surfaces. The rafters should be pulled together with a bolt or hairpin, nails. This connection is used by many masters in practice.
In general, it is possible to install rafters on a Mauerlat by creating structures for roof truss systems that are expansion or non-expansion. This determines the choice of the appropriate method of connecting the power plate and rafters, which can be similarly strengthened to the ridge.
The main shortcomings in the installation of attachment points for the truss system
The problem of choosing the method of attaching the truss system to the structure of the building is very important when creating attachment points. Often, when creating nodes, the Mauerlat serves as a support for the rafters. The fastening of the Mauerlat beam is carried out “tightly” with the help of anchor bolts to the reinforced stiffening belt.
A possible drawback is an unanchored stiffening belt, which can lead to the overturning of the Mauerlat beam and the stability of the roof truss system. There is a loosening of the roof, and the roof is sliding down. Due to erroneous placement of anchor bolts or incorrectly made holes, the fastening is no longer effective.
If the nuts are screwed onto the bolts with an overtightening, then the fastening assembly becomes fragile and is subject to rapid destruction. In this case, wire twisting is sometimes used to create an attachment point.
During the construction of the truss system, the safety of the joints should be observed.
For example, if the truss structure is combined with the floor without taking into account the bearing capacity of the attic floor, then this is the most dangerous moment that can lead to the destruction of the building.
If the tightening is changed to a precast concrete floor beam intended for bending, then the use of precast concrete beams should be effective due to their rigid fixation in the reinforced floor stiffener, which is arranged using a reinforcing cage. Its axis must go in the same direction as the acting forces.
At the same time, the presence of shortcomings in the process of creating a truss system, which is a supporting wooden floor structure, often arises due to a misunderstanding of the functions performed by the puff and crossbar in the entire roofing system. The puff differs from the crossbar in that it is a longitudinal, and the crossbar is a transverse beam.
The construction of the truss system is associated with the creation of a spacer system that works on the principle of divergence at the bottom of the planes, which occurs under the influence of not only their own weight, but also the load that falls on the line of intersection of the planes, which should be prevented by the transverse beam, that is, tightening.
Getting to the roof device, you should find out all the points associated with the assumption of certain errors that occur when performing work on the installation of the truss system. The device of the roof of the house is associated with possible difficulties and shortcomings that do not allow achieving the goal.
When designing any residential building, architects pay special attention to the roof, as it performs not one, but several functions at once, depending on its design features. It must be said that not all future homeowners are satisfied with the usual gable roof, although it can be called the most reliable, since it has only two pitched planes and one joint between them. Many are attracted to more complex designs that add a special appeal and originality to the structure. Other, more practical homeowners prefer attic structures that can simultaneously serve as a roof and a second floor.
The basis of any roof is an individual truss system, which has its own design features. Making the choice of the desired roof frame will be much easier if you figure out in advance which ones types and schemes of truss systems used in building practice. After receiving such information, it will become more clear how complex such structures are in installation. This is especially important to know if the roof frame is supposed to be built independently.
The main functional tasks of truss systems
When arranging pitched roof structures, the truss system is a frame for covering and for holding materials of the "roofing pie". With proper installation of the frame structure, the necessary conditions will be created for the correct and non-insulated types of roofs that protect the walls and the interior of the house from various atmospheric influences.
The roof structure is also always the final architectural element of the exterior design of the building, supporting its stylistic direction with its appearance. Nevertheless, the design features of the truss systems must first of all meet the requirements of strength and reliability that the roof must meet, and only then - aesthetic criteria.
The frame of the truss system forms the configuration and angle of inclination of the roof. These parameters largely depend on the natural factors characteristic of a particular region, as well as on the desire and capabilities of the homeowner:
- The amount of precipitation in different periods of the year.
- Direction and average wind speed in the area where the building will be erected.
- Plans for the use of the space under the roof - arranging residential or non-residential premises in it, or using it only as an air gap for thermal insulation of the premises below.
- Variety of planned roofing material.
- Financial capacity of the homeowner.
Atmospheric precipitation and the strength of wind currents give a very sensitive load on the structure of the roof. For example, in regions with heavy snowfalls, you should not choose a truss system with a small angle of inclination of the slopes, as snow masses will linger on their surface, which can lead to deformation of the frame or roofing or leaks.
If the area where the construction will be carried out is famous for its winds, then it is better to choose a structure with a slight slope of the slope so that the sharp gusts that occur do not rip off individual elements of the roof and roof.
The main elements of the roof structure
Details and nodes of truss systems
Depending on the chosen type of truss system, the structural elements used can vary significantly, however, there are details that are present in both simple and complex roof systems.
The main elements of the pitched roof truss system include:
- Rafter legs forming roof slopes.
- - a wooden bar fixed on the walls of the house and serving to fix the lower part of the rafter legs on it.
- The ridge is the junction of the frames of two slopes. It is usually the highest horizontal roof line and serves as a support on which the rafters are fixed. The ridge can be formed by rafters fastened together at a certain angle or fixed on a ridge board (run).
- Lathing - these are slats or beams mounted on rafters with a certain pitch and serving as the basis for the flooring of the selected roofing material.
- Retaining elements, where you can take beds, girders, racks, struts, ties and other parts, serve to increase the rigidity of the rafter legs, support the ridge, link individual parts into a common structure.
In addition to the structural details mentioned above, other elements can be included in it, the functions of which are aimed at strengthening the system and optimal distribution of roof loads on the walls of the building.
The truss system is divided into several categories depending on the different features of its design.
attic space
Before proceeding to the consideration of different types of roofs, it is worthwhile to figure out what an attic space can be, since many owners successfully use it as utility and full-fledged living quarters.
The design of pitched roofs can be divided into non-attic and attic. The first option is called just that because the space under the roof has a small height and is used only as an air layer that insulates the building from above. Such systems usually include or have several slopes, but located at a very slight angle.
The attic structure, which has a sufficiently large ridge height, can be used in different ways, be insulated and not insulated. These options include attic or gable option. If a roof with a high ridge is chosen, then it is imperative to take into account wind loads in the region where the house is built.
Slope slope
To determine the optimal slope of the roof slopes of the future residential building, first of all, you need to look at the already built low-rise neighboring houses. If they have been standing for more than one year and steadfastly withstand wind loads, then their design can be safely taken as a basis. In the same case, when the owners set the goal of creating an exclusive original project, unlike the buildings standing nearby, it is necessary to familiarize yourself with the design and operational features of various truss systems and make appropriate calculations.
It should be borne in mind that the change in the tangent and normal values of the wind force depends on how large the slope of the roof slopes is - the steeper the angle of inclination, the greater the importance of the normal forces and the smaller the tangents. If the roof is sloping, then the structure is more affected by the tangential wind load, since the lifting force increases on the leeward side and decreases on the windward side.
Winter snow load should also be taken into account when designing the roof. Usually this factor is considered in combination with the wind load, since the snow load on the windward side will be much lower than on the leeward slope. In addition, there are places on the slopes where snow will definitely collect, giving a big load on this area, so it should be strengthened with additional rafters.
Roof slopes can vary from 10 to 60 degrees and must be selected not only with regard to the consolidated external load, but also depending on the roofing that is planned to be used. This factor is taken into account because roofing materials differ in their mass, their fixing requires a different number of elements of the truss system, which means that the load on the walls of the house will also vary, and how large it will be, also depends on the angle of the roof slope. Equally important are the features of each coating in terms of resistance to moisture penetration - in any case, many roofing materials need one or another slope to ensure the free flow of storm water or melting snow. In addition, when choosing a roof slope, you need to think in advance how the process of cleaning and repair work on the roof will be carried out.
When planning a particular angle of the roof slopes, you need to know that the fewer joints between the sheets of the coating, and the tighter they are, the less you can make the slope of the slope, of course, if it is not supposed to arrange a residential or utility room in the attic space.
If a material consisting of small elements, for example, ceramic tiles, is used to cover the roof, then the slope of the slopes must be made steep enough so that water never lingers on the surface.
Given the weight of the roofing material, you need to know - the heavier the coating, the greater the angle of the slopes should be, since in this case the load will be correctly distributed to the rafter system and load-bearing walls.
The following materials can be used to cover the roof: either a profile sheet, galvanized steel, corrugated asbestos-concrete and bitumen-fiber sheets, cement and ceramic tiles, roofing felt, soft roofing and other roofing materials. The illustration below shows the allowable slope angles for various types of roofing.
Basic structures of truss systems
First of all, it is worth considering the basic types of truss systems regarding the location of the walls of the house, which are used in all roof structures. The basic options are divided into layered, hanging, and also combined, that is, including elements of both the first and second types of systems in their design.
fasteners for rafters
Layered system
In buildings where internal load-bearing walls are provided, a layered truss system is often installed. It is much easier to install than a hanging one, since the internal load-bearing walls provide reliable support for its elements, and in addition, fewer materials will be required for this design.
For rafters in this system, the defining reference point is the ridge board, on which they are fixed. The non-thrust type of the layered system can be equipped in three versions:
- In the first version, the upper side of the rafters is fixed on a ridge support, called a sliding one, and their lower side is fixed by cutting to the Mauerlat. Additionally, the rafters in the lower part are fixed to the wall with wire or staples.
- In the second case, the rafters in the upper part are cut at a certain angle and interconnected using special metal plates.
The lower edge of the rafter legs is attached to the Mauerlat with movable fasteners.
- In the third version, the rafters are rigidly fastened in the upper part with bars or processed boards located horizontally, parallel to each other on both sides of the rafters connected at an angle, and a ridge run is pinched between them.
In the lower part, sliding fasteners are used to fix the rafters, just as in the previous case.
It is necessary to explain why sliding fasteners are often used to fix the rafters on the Mauerlat. The fact is that they are able to save the load-bearing walls from excessive stress, since the rafters are not rigidly fixed, and when the structure shrinks, they have the ability to move without deforming the overall structure of the roofing system.
This type of fastening is used only in layered systems, which also distinguishes them from the hanging version.
However, in some cases, a spacer system is used for layered rafters, in which the lower end of the rafters is rigidly fixed to the Mauerlat, and in order to remove the load from the walls, puffs and struts are built into the structure. This option is called complex, as it includes elements of a layered and hanging system.