The rafter system of a gable roof is a simple design that can be installed with your own hands even by a novice developer. You just need to make preliminary calculations, familiarize yourself with the details and stages of roof construction, and calculate the materials needed for installation. When making calculations, it should be taken into account that the load-bearing capacity of a gable roof depends on the influence of loads from wind, snow, and the weight of materials on it.
To make the process of building a gable roof rafter system as easy as possible for you, below is detailed step-by-step instructions for installing a rafter system with your own hands.
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Requirements for building materials
For the installation of a rafter system, the best option would be to use lumber from coniferous wood - pine, spruce or larch, grades I - III.
The material for the rafters is taken at least grade II, the mauerlat is made from boards or timber of grade II, material of grade II is taken for racks and purlins, the sheathing is made from lumber of grades II-III, it depends on the roof. Crossbars and tie-downs are made of Grade I material. Grade III material can be used on linings and linings.
Note! The lumber must be dry with a moisture content of no more than 20%. Before installation, it should be treated with fire retardants and antiseptics against fungal diseases.
Lumber should be stored under a canopy, providing protection from the sun and moisture. Level the storage area and cover the lumber with pads for ventilation.
For installation you will need fastening elements: ties, plates, studs, bolts with washers and nuts, self-tapping screws with EPDM gaskets, 2.8 mm thick, mounting tape, galvanized brackets.
Brackets are used when attaching the Mauerlat; they are secured with nails or self-tapping screws.
KR corners serve to attach the rafters to the mauerlat and prevent the rafters from moving.
All fastening material must be made of high quality material and be protected against corrosion.
Tools for constructing a rafter system
To install a gable roof rafter system, you will need the following set of tools:
- tape measures of different lengths 5, 10, 20 meters;
- markers, pencils;
- cord for tensioning;
- hammers, for various purposes, nail puller;
- scissors, for cutting;
- roofing knife;
- putty knife;
- scotch;
- hacksaws, electric saw, electric drill with various drills and attachments;
- screwdriver with attachments;
- markings, horizontal and vertical levels;
- slats, rulers;
- polyurethane foam;
- safety belt and rope - for safe work.
Keep all tools on the roof in a tool bag for safety reasons.
Types of rafter systems for a gable roof
Sent rafters
They rest on the mauerlat and racks installed on the internal wall, with a pitch equal to the rafters. To provide rigidity for spans of 6 m, additional struts are installed.
Scheme of layered rafters of a gable roof
Hanging rafters
If the building is small in width, you can arrange a rafter system where the rafters rest on the mauerlat or walls, without intermediate supports. The maximum span is 9 meters. Such roofs can sometimes be installed without a Mauerlat. The rafters are installed on the wall using spacers; in this embodiment, a bending moment acts on the rafters.
To unload, wooden or metal plates are installed. They securely strengthen the corner. For hanging rafters of a larger span, a headstock and struts are installed. For hanging systems, the rafters are made with a larger cross-section, and lumber is chosen at least grade I II.
Scheme of hanging rafters of a gable roof
Calculation of the rafter system
You can determine the cross-section of a gable roof beam required in a rafter system by collecting all the loads acting on it: the weight of the covering, sheathing, snow, wind pressure, precipitation.
Constant loads can be determined by the weight of 1 m 2 of roofing and sheathing. It is important that the weight per 1 m 2 of roofing be in the range of 40-45 kg.
Variable loads from snow and wind are calculated using tabular values of SNiP normative documents, depending on the height of the building and temperature zone. The load from snow is equal to its weight multiplied by a coefficient depending on the slope of the slope. All these calculations are performed during the project.
What if there is no project and the roof is being erected on a small building? You need to look at the construction of a house in the neighborhood, which is being carried out according to a design whose roof area is the same as your building. The gable roof rafter system will serve as a model.
Dimensions of timber for rafters
At the top point a ridge is laid that connects the rafters. The height of the ridge depends on the slope of the roof. The slope is affected by the choice of coating material. The minimum sizes are:
- for tiled roofs, slate 22 gr.;
- for metal tiles - 14 g;
- ondulin - 6 g;
- corrugated sheeting - 12 gr.
The optimal angle is 35-45 degrees. tilt, ensures rapid discharge of water and snow. In regions with strong winds, the roofs are made flat and then the angle of inclination is within 20-45 degrees.
The height can be determined using the formula: H=1/2Lpr*tgA. Where A is the angle of inclination, L is the width of the building.
The task is simplified when using a ready-made table. The coefficient depends on the width of the building and the angle of inclination. Multiply the coefficient by 1⁄2 the width of the building.
The rafters are made from pine or spruce bars, with a section of 50x100 mm, 50x150 mm.
The size of the rafters depends on the pitch. The pitch of the rafters is smaller, a larger number is installed, and the cross-section will decrease. The distance between the rafters on a gable roof ranges from 600 mm to 1800 mm, it all depends on the design of the roof and the materials used for its construction.
|
Length rafters, mm |
Distance between rafters, mm | Rafter beam cross-section size, mm |
| up to 3000 | 1200 | 80×100 |
| up to 3000 | 1800 | 90×100 |
| up to 4000 | 1000 | 80×160 |
| up to 4000 | 1400 | 80×180 |
| up to 4000 | 1800 | 90×180 |
| up to 6000 | 1000 | 80×200 |
| up to 6000 | 1400 | 100×200 |
The roof does not end at the level of the walls; it is extended outward by 500 mm. The rafter leg can protrude, or a board or block can be built up. In this case, moisture does not reach the wall and the foundation is not poured.
Step-by-step installation of a gable roof truss system
The rafter system of a gable roof consists of the following elements:
- Mauerlat.
- Lay down.
- Racks.
- Rafters.
- Struts.
- Puffs.
- Lathing.
Mauerlat installation
Fastening the Mauerlat to a monolithic reinforced concrete belt
Mauerlat evenly distributes the load on the walls of the building; its installation can be done in several ways:
- attached to the wall through a reinforced concrete belt with studs;
- studs are inserted into the masonry;
- a simple and common method for simple roofs, fastening with wire rod.
For it, take a beam with a cross section of 100×100 mm, 150×150 mm or 200×200 mm. Which section to choose depends on the size of the roof and its covering. The Mauerlat is joined along its length; to do this, make 100 mm cuts, 500 mm long, fold the bars and fasten them with pins.
In the corners, the mauerlat is tied with notches into the floor of the timber, fastened with staples or bolts. For wooden buildings, the Mauerlat is the last crown. On brick walls, make a monolithic reinforced concrete belt with a cross-section of 400×300 mm. Along the belt, place threaded pins 12 mm in diameter, every 120 mm, for fastening.
Drill holes with a diameter of 12 mm in the Mauerlat, lay them so that the pins go into the holes. Tighten the top with nuts. First, we lay two layers of roofing felt or roofing felt under the block. On the outside of the wall, lay the mauerlat with bricks. Lay the Mauerlat on a horizontally and vertically level base. You need to check with a level that the surface is horizontal. Check diagonals. If necessary, level with pads.
Installation instructions for beds, racks, rafters, struts and tie rods
The installation of a gable roof rafter system with your own hands is carried out in the following order:
- Install the beam with the rafters in place.
- Mark the installation step of the rafter legs.
- Prepare according to the size of the rack.
- Install them, if necessary, with spacers.
- Lay the purlin. Check geometry. Install fasteners.
- Try on the first rafter leg and mark the cutting areas.
- Mark the points and install the rafters at the beginning and end of the roof, stretch the cord between them in order to align the remaining elements along it.
- Having installed the rafter leg, we first attach it to the mauerlat, then to the ridge purlin, to each other.
- Screw each second leg to the mauerlat with wire.
The rafters are fastened to the mauerlat using notches, stop corners and a hemmed support bar. Secure with nails or staples.
Methods for attaching rafters to the Mauerlat
Install the support posts on the beds or pads and overlays. A log is a beam 50×100 mm or 50×150 mm, laid on the middle wall along a layer of roofing felt. Place brick pillars under the linings, 2 bricks high.
The rafter legs are connected to each other at the ridge. Let's consider the common connection nodes of the rafter system:
- They make cuts at one leg and cut down at the other. Insert one leg into the cut of the other and fasten with a bolt.
- Install overlays, wooden or metal.
- Using notches in the purlin, they are secured with nails or bolts.
Methods for connecting rafters on a ridge
To ensure the roof's resistance to wind loads, tie-rods, struts and purlins are installed. The tightening is a 100×150 mm block, purlins and struts are made from a 50×150 mm or 100×150 mm block.
With the installation of contractions, the reliability of the rafter structure increases. The sections of the timber are the same as the rafters. They are attached to the legs with bolts or nails. The device of struts adds rigidity to the structure. They are installed tightly to the surface of the rafters
The lumber has a standard length of 6 m. The rafters can be longer. Then you need to dock them. There are several connection methods:
- Fasten by placing bars on both sides at the junction, connecting them with nails in a checkerboard pattern.
- Connect with an overlap, one part of the rafters to another, at a distance of 1 meter, fasten with nails in an alternating order.
- Make a cut obliquely, cut out part of the rafter legs, connect them, strengthening them with bolts.
Sheathing device
Lathing is installed along the roof rafters. It serves to distribute the load from roofing material and snow onto the rafters. Plays the role of an air gap between the roof and the rafter system.
The design of the sheathing depends on the roofing material used:
- under the soft tiles, make the sheathing continuous, lay an anti-condensation film on the rafters, press it on top with a counter batten, nail the sheathing onto it, then OSB boards and underlayment carpet, lay the tiles on top.
- Under the roof made of corrugated sheets, the sheathing should be sparse. The pitch of the sheathing depends on the brand of corrugated sheeting, its thickness and the angle of inclination of the roof.
- The lathing for standard slate should be made in increments of 500 mm from a bar of 75×75 mm or 50×50, as well as boards from 30×100 mm. The design features of the roof should be taken into account when making the final choice of the appropriate option.
The lumber from which the sheathing is made is first or second grade pine. It is advisable to take the width no more than 14 cm. With a wider width, the boards may warp and damage the roofing. The length of the nails should be three times the thickness of the sheathing. Lay the boards along the ridge. Install the first board of greater thickness to the height of the roofing.
Install continuous sheathing along the roof slope.
The first layer is to place a board along the ridge from it at a distance of 500-1000 mm to the next one and so on. Lay the second layer of sheathing along the rafters. Place the joint between the boards only on the rafters at intervals. Sink the nail, head and all, into the flesh of the wood.
Cornice overhangs
They are installed to protect from precipitation and play an aesthetic role. Eaves overhangs are arranged tightly without gaps. The final stage of installing the roof.
Diagram of the eaves overhang of a gable roof
Gable
The gable roof has two gables. They have the shape of a triangle, with the apex at the ridge and the sides coincide with the slopes of the roof. The gables support the rafters and enclose the attic space. They protect from wind and precipitation and provide stability to the roof.
In wooden buildings, the pediment is framed. In brick buildings, frame or brick. Gables made of brick or gas block are erected before the roofing is installed. They require very precise execution.
Frame pediments fit into the finished opening when the rafter system is already assembled.
The frame is made of bars or boards. The frame elements are connected on tenons or in the wood floor, all fastened with nails. They are sheathed by nailing boards, lining or siding, maintaining the color scheme in the decoration of the building facade. To construct a window opening, an additional frame is made under it according to the size of the window. If the attic is insulated, then the gable also needs to be insulated. The insulation is placed in the middle of the frame. Mineral wool insulation with reduced flammability is used. On the outside, the frame is covered with a hydro-windproof film or windproof membrane; on the inside, a vapor-proof film or a vapor-proof membrane is nailed under the finishing material.
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The rafter system is the roof frame, which is the basis for laying roof coverings.
The rafter system is designed to withstand the load of the roof, taking into account natural loads: winds, snow, rain.
The roof option is approved at the design stage.
The purpose of the roof includes several functions: warmth in the house, protection of the premises from natural phenomena, therefore The rafter system needs to be given special attention.
You can read how to calculate the rafter system.
It is customary to classify rafter systems so that the task of choosing a future roofing option is solved easier:
- Single-pitch. The simplest ones. More suitable for utility rooms, bathhouses, small private houses, gazebos. Provides for an inclined position of the structure at a slight angle (no more than 25°);
- Gable. Used for small houses and country houses. They have the form of a triangle, in which the rafter boards are connected by a beam and are at a certain angle;
- Gable broken lines. They have two slopes with a fracture, thanks to which there is an opportunity to increase the attic area;
- Three-slope (half-hip). They have two trapezoid-shaped slopes, which are connected by one end triangular slope (hip);
- Four-slope (hip). Used for residential buildings, require significant labor costs. They have two end triangular slopes and two trapezoidal ones;
- Tent. Used for square-shaped buildings. They consist of four triangular slopes, the upper corner of which is connected in the center of the roof;
- Multi-pincer. Consist of trapezoidal or other slopes of various shapes, connected to each other.
The most suitable designs for - and broken gable. There are others, but they are less common and not as practical as the above.
Rafter structures are also classified into:
- Hanging. With this type of roof frame due to the lack of load-bearing walls in the room;
- Layered. Rafter installation option, providing support on a load-bearing internal wall or support in a building.
When designing a building, the material for the roof frame is calculated based on the intended configuration and load. It’s not difficult to make rafters for yourself, it’s important to approach the matter wisely.
Rafter systems of layered and hanging type
Calculation of the load on the rafters
To correctly calculate the load on the rafters, it is necessary to take into account many factors that can affect the weight of the structure.
Important indicators to consider:
- Constant load: includes the mass of the roofing pie and covering material;
- The load is temporary: constant and maximum amount of snow, rain, intensity of wind gusts, and in areas with high seismic activity - the effect of storm winds, tornadoes, hurricanes.
In addition, you should keep in mind the weight and strength of the rafter legs, and also pay attention to the fastening of the gable roof rafters and the installation option.
Scheme of rafter systems
The distance between the rafters of a gable roof and the thickness of the rafters
The rafter pitch of a gable roof is the empty space between the rafters. The functionality of the roof depends on the correct calculation of the pitch. As a rule, the step is about a meter.
To more accurately calculate the distance between rafter boards, there is a specific calculation scheme:
- Determine the length of the slope.
- The length of the slope is divided by the distance between the rafters.
- To determine the number of rafters, one is added to the resulting value and rounded up. This is how they determine how many boards are needed for the slope.
- The length of the slope is divided by the number of boards to obtain the distance between the rafters.
This calculation is not always final.
Additionally, you should take into account the load of the roofing (its weight), the thickness of the rafters, as well as the dimensions of the rafters for a gable roof.
The thickness of the rafter board largely depends on the covering material:
- . Boards are used with a cross-section of 5x20 cm at a pitch of 60 to 90 cm with a sheathing section of 4x5 cm;
- . Rafter boards - 5x15 cm, pitch - from 60 cm to 95 cm;
- . The section of the board is 6x18 cm or 5x15 cm, the distance between the bars is from 80 cm to 130 cm;
- . Rafter cross-section - 5x15 cm, 5x10 cm with pitches from 60 cm to 90 cm;
- . The cross-section of the timber is the same as for corrugated sheeting at a pitch of 60-80 cm.
All indicators should be taken into account and the thickness of the rafters should be accurately calculated so that there is no excessive load on the foundation.
Incorrect calculation of the length of the gable roof rafters, as well as incorrect calculation of the pitch indicators, can lead to sagging of the roof.
Installing the rafters of a gable roof with your own hands requires taking into account the weight of the rafter board and all additional fastenings of the structure.
What does the rafter system consist of?
Rafter structure - a complex system and installing a gable roof rafter system is not an easy task. Rafter system consists not only of rafter boards, but also of other additional elements:
- Mauerlat. An element that distributes the entire load evenly across the supports;
- Run. Boards holding the legs of the rafters together: at the top - a ridge, at the side - a side girder;
- Puffs. A connecting beam that prevents the rafter legs from diverging;
- Struts, racks. The bars, which fix the stability of the rafters, resting on the bed;
- . A lattice made of bars, which is applied perpendicular to the rafters. Transfers the load of the covering material to the rafter frame;
- . A connecting beam that serves as a connection between the roof slopes;
- Fillies. If the length of the rafter legs is insufficient, they are mounted to form an overhang;
- Roof overhang. Extends beyond the bottom line of the slope to prevent precipitation from entering the walls.
The rafter system involves rafters, braces, braces and racks located in the same plane. They are located in such a way that the main load of the roof structure falls vertically on the external load-bearing walls. Therefore, the manufacture of gable roof rafters is a very important process.
What does a gable roof truss system consist of?
Installation of a rafter system with layered rafters
A layered rafter system is used when the span length does not exceed 6.5 meters.
If there are load-bearing structures inside the building, it is possible to install additional racks.
The main support of the rafter legs is the mauerlat.
Mauerlat installation
Before installing the Mauerlat, it is necessary to install an armored belt. It consists of formwork, into which reinforcement is laid and filled with concrete. At the base, when the concrete has not yet hardened, studs are installed, to which the Mauerlat is then attached.
Mauerlat is a beam that is laid on a support (load-bearing wall) and is the base of the rafter frame. A layer of waterproofing material is pre-laid. If the length of the beam is not enough to cover the length of the wall, then it is increased.
- Check the equality of the diagonals. A discrepancy of a few centimeters can lead to refurbishment of the frame;
- Secure the corners of the Mauerlat;
- Attach the Mauerlat using pins or wire. The studs are tightened in two steps, having previously drilled holes for them.
The stability of the roof structure depends on how firmly the Mauerlat is installed.
Therefore, it is necessary to take seriously the attachment of the Mauerlat to the supporting support.
Mauerlat installation
Sill
After the Mauerlat has dried (after 5 days), mark the installation of the plank on the Mauerlat timber: its axis should be equally spaced on each side of the mauerlat beam. The bed is attached to a two-layer waterproofing layer with anchor bolts. The bench should be secured to the wall from the inside with twisted wire or staples. Next, markings are made for installing the rafters.
Installation of a gable roof rafter system
The supporting points of layered rafters are the walls and racks inside the frame. The rafters are mounted with hinged fastening units. When using sliders for fastening, a slight lowering of the roof frame is ensured in the first years of the roof's service.
This installation method is necessary to prevent distortions, since in the first years the building settles a little.
The rafter beams should be secured either by installing them in prepared grooves and strengthening them with fasteners, or by attaching board overlays.
Installation of rafters
Ridge knot
The rafters are connected end-to-end by cutting the edge of the beam so that the angle when connecting the opposite beams corresponds to the angle of the slope.
They hammer the rafters under the ridge with nails. An option is possible in which the beams are connected with bolts, nails or pins, that is, with an overlap.
If necessary (if provided for by the project), a cut is made in the rafter beams to attach the ridge beam (purlin).
Ridge knot
Racks
The racks are attached with a short span - in the center, on the sides and in the center - with a wider roof base. The fastening is carried out vertically from the ridge to the inner wall.
Run
Purlin - a connecting beam for securing rafter legs. Attaches with bolts or brackets to the rack.
The final stage of installation of the roofing system is the installation of fillets with a short length of rafter legs for the overhang. To install the canopy, it is necessary to install additional small rafter boards.
Installation of a rafter system with layered rafters
DIY gable roof rafter system: installation with hanging rafters
Rafter system, equipped with hanging rafters, is a triangular structure, where the sides are rafters, and the base is a tie connected to the lower heels of the rafters.
Installation of a hanging type rafter frame can be done without installing a Mauerlat: a board that is fixed to a two-layer waterproofing can replace it.
If the structure has a large span, then struts, headstocks, and crossbars are attached to it.
There are no racks in the hanging system.
Puffs
The tie is the longest beam of the roof frame. To prevent it from sagging, it is necessary to attach headstocks - boards that are attached to the top of the structure on one side, and to the tie on the other. Fastened with bolts or wooden plates. Using threaded clamps, you can adjust the sagging tightening.
Construction of the rafter system
Installation of strut beams
The headstock can be complemented by strutted beams, forming a rhombus, where two struts are the lower sides, and the rafter boards are the upper ones, the upper corner being the ridge. Thus, the struts rest against the headstock, distributing the load.
Strut beams
Rafters
The rafters of a hanging structure are mounted similarly to a layered structure. When installing attics, the tie is installed closer to the ridge, providing more space under the ceiling. In this case, the tightening is secured by cutting and bolting.
ATTENTION!
When installing a hanging system, a prerequisite for installation is the accuracy of calculations and the strength of the rafters and tightening.
The presence of errors leads to displacement of the axes of system elements, which ensures distortion of the structure.
This photo will tell you how to install rafters for a gable roof:
Installation of rafters
Hanging rafters
How to strengthen the rafters of a gable roof
It is necessary to strengthen the rafters of a gable roof when the load calculation is incorrect or frame defects are detected.
Strengthening can be done using:
- Beams, which are installed to transfer the load to them;
- Installation of struts with an inclined mount with a rest rest;
- Application of double-sided slats;
- Increasing the cross-section of rafter beams in the place of supports on the strut by applying sheathing from boards with nails or bolts;
- Wall made of boards, which are attached to the rafters in places where snow accumulation is expected to increase the load-bearing capacity of the rafters.
You can resort to strengthening the mauerlat beam and the base of the rafter beam. Due to increased humidity and reduced ventilation, these parts of the frame are more susceptible to rotting, so when arranging the roof special attention needs to be paid
Are you already at the finish line in building your dream home, and it’s time to understand the intricacies of the rafter system? Let's just say: pleasant worries await you: calculating the angle, weight and safety factor of the rafters, an agreement with a familiar craftsman or company, or preparing all the necessary tools for independent carpentry work.
And so that tomorrow all these worries do not become a headache and you do not worry about whether this or that knot is being done correctly, we have prepared this article for you. So, let's figure out how to make high-quality rafters for a gable roof with your own hands so that it is no worse than purchased ones.
- Short production times.
- Technological precision of all details.
- Identical, already adjusted dimensions of all structural elements.
But then be prepared for the following disadvantages:
- High cost (at least twice as much as if you planed the rafters yourself).
- Delay in delivery (especially during the season).
- Using low-quality or under-dried wood (and then the roof will “sink”).
So convenience or quality? If this is not your first time carving or planing something out of wood, feel free to take on making rafters! Here's what it all looks like in real life:
In the construction world, in simple terms, rafters are usually divided into the main ones, i.e. load-bearing ones, on which the roof is supported, and auxiliary ones, which are located inside the roof and serve as support for hemming the ceiling and walls of the attic (if one is planned). The strength and reliability of the future roof depends on how accurately and correctly you calculate the rafter system in advance.
The rafter system of any gable roof itself consists of the following basic elements that you need to make:
- Mauerlat.
- Vertical racks.
- Crossbars.
- Rafter legs.
- Spacers.
- Ridge run.
It is better to entrust complex roofing structures with multiple elements to a professional, but you can handle a small roof of a private house. To do this, you will need these simple formulas that will help you find out how thick the rafters should be, with what slope and what span:
How to draw up a project for a future roof?
The golden rule in roof construction is to measure seven times and cut only once. And first of all, it is important for you to understand that each rafter leg has its own individual location. Therefore, first, be sure to draw up a detailed project, and preferably in a special program. Only after this, using your 3D model of the future roof, mark exactly where and what kind of connections the rafters will have with the Mauerlat and with each other.
It is important to determine as accurately as possible the angle of inclination of the rafters and at what angle they need to be cut. And don’t worry about how to make all these rafters for a gable roof yourself: all you need is a regular machine.
Determining the angle of inclination of the roof: calculating the loads
The angle of inclination of a gable roof is made from 5° to 90°. But the most proven and standard option is 35°-40°, where loads are distributed most rationally and building materials are consumed.
Straight slopes are built when in the future there will be only a non-residential attic under the roof, the main function of which is ventilation and regulation of heat exchange. But when the under-roof space is planned to be residential, attic, they initially plan a so-called sloping gable roof. Its difference is that the slopes in the middle have a kind of kink, which changes their angle to a steeper one. This design is quite suitable both for arranging an attic and for protecting the entire house from bad weather.
Please note that most roofing materials are only suitable for pitches greater than 45°.
Constant and variable roof loads
The same loads determine what rafter pitch you need for your gable roof. This table will help you choose the right section of rafter legs:
Indicators of rafters for deflection
Even strong-looking rafters may not be suitable for constructing the roof of a residential building due to the fact that they have insufficient deflection properties. There are separate paragraphs in the SNiP section called “Loads and Impacts”.
And the easiest way to increase the deflection strength of the rafters is to make the cross-section larger. It’s a little more difficult to strengthen it with a special beam, bringing its edge to the strut.
Reinforcing elements for rafters
The more racks, struts and contractions, the more durability and stability the entire rafter system has.
If you have a suspicion or even an accurate estimate that a simple roof structure will not withstand future loads, make additional reinforcements for it. Such prevention will never hurt, but it will save you from many problems. Note that it is especially offensive when the garage roof falls in - right on top of the car. And such problems are not a joy for a residential building.
The rigidity of the rafter structure is enhanced by struts, additional purlins and support posts. The braces are designed to reduce the span of the rafter legs. Their angle of inclination to the horizontal is usually at least 45°.
A purlin is a horizontal beam that is parallel to the ridge and secured to vertical posts. More details in the video:
Determining the type of roof: cold or warm?
And now about the concept of the attic. If you are building a roof for a bathhouse or a small utility room, it can be done using the most simplified technology - install rafters, connect them at the ridge and cover them with sheets of roofing felt. But for the roof of a residential building, where ventilation is important, this principle cannot be used. There will already be at least three levels:
- The upper or first level of the rafters is about 200 mm.
- The average one is always equal in height to the auxiliary rafters.
- The third one is already on the edge of the wall.
This makes it convenient to install insulation, because the roof of a residential building is characterized by the fact that heat rises upward and, in the absence of thermal insulation, the roof covering is constantly heated.
The result: in winter, the snow melts and slides down, freezing and accumulating even more at the cold cornice. This causes a lot of problems: long dangerous icicles, a clogged drainage system, and the gradual destruction of the entire roof. Decide for yourself!
Determine the type of rafter system: layered or hanging?
So, now is the time to think about the support bases for future rafters, which also need to be prepared in advance and on which many parameters of the roof itself will depend. Thus, rafters are divided into layered, hanging and hybrid.
Hanging rafters are usually the lot of small and light roofs, the distance between the supports does not exceed 6 meters. But in buildings with a load-bearing middle wall or additional supports, layered rafters are installed to strengthen the roof. Or this combined option:
Another difference is that the hanging rafter system forces the Mauerlat to work in compression, while the layered rafter system works for shear. But the main task of both layered and hanging rafters is to transfer the loads of the entire roof to the walls and foundation as evenly as possible.
Selecting material for rafters
So, if you have decided on future loads, it’s time to choose the right material. The following are usually used for making rafters:
- Wood. Solid wood, boards or laminated veneer lumber.
- Lightweight metal profile. We are talking about galvanized steel profiles.
- Black metal. These are I-beams and steel channels.
- Heavy reinforced concrete structures for industrial construction.
Dry board: economical option
If large loads are not expected on the rafter system, then make the rafters from dry planed boards with a small cross-section. But if knee-deep snow is not uncommon in your area and the roofing material is not light, then you will have to make some of the component elements glued. That's the whole difference.
It is most convenient to make elongated side rafters and diagonal rafter legs from the board. So, a 40 mm thick board, which is often used for outbuildings, is not suitable for a roof. At least 50 mm! Moreover, the longer the rafter leg is planned, the wider the board itself should be. So, rafters 6 meters long will have to be made from boards 150 mm wide, and even longer ones - from boards 180 mm wide.
For the roof of a frame house, this is truly one of the best options!
And also rafters made from boards are the most economical, and at the same time they are almost as strong as lumber. It is only important to choose the right section and use high-quality material. Therefore, when purchasing material, be sure to take with you a special device for measuring wood moisture content and use it. There is nothing worse than damp rafters. And it’s not just a matter of future mold: such a roof will begin to warp and warp, because this material changes its shape when it dries. The fastenings at the rafters will fly off and even the covering of your gable roof will bounce off in places. In a word, there will be no problems!
But it is most convenient to splice rafters along the length from a regular board:
Durable metal: resists moisture
And, you will be interested to know that rafters can be made not only from wood! Thus, iron rafter systems, which were once used exclusively for industrial construction, are regaining their former popularity today. And, let us note, this roofing material has many advantages, the most valuable of which is the complete absence of fungus from dampness. After all, the space under the roof most often “pleases” with random leaks.
And the work itself with such rafters during installation is no more difficult than with wooden ones - see for yourself:
Beams: the benefits of high-quality wood
The timber is more durable, but the disadvantage is that it has a lot of weight and you have to make cuts at the fastening points. For a log this is not only a problem, but also some loss of the load-bearing capacity of such a rafter leg. But so far this material is the most popular for making rafters.
Most suitable for the manufacture of rafters is lumber that meets the requirements of GOST 8486-86 or 2695-83. And this:
- Humidity no more than 18%, measured with a moisture meter.
- Cracks that are not through and do not exceed half the length of the board.
- For each linear meter - no more than three knots, and each of them - no more than 30 mm in diameter.
Therefore, when purchasing wood for rafters, be sure to check the documents from the seller, which indicate the quality of the product.
The type of wood is also important. The fewer knots and cracks there are on the beams, the better. Some varieties also boast good moisture resistance and resistance to rot and pests. For the roof this is what you need. Therefore, we recommend making rafters from coniferous wood, which is rich in resin, and resin is a natural barrier against rotting. But special processing is still needed.
And also take into account this fact: when manufacturing a rafter system, you need to purchase 5-7% more material than necessary, because it will not always be possible to make an ideal rafter cut or notch of the required depth. There will still be overspending, so stock up on it in advance so that you have wood of the same moisture content and properties for the entire rafter system.
Otherwise, if you had to purchase some individual roof elements separately, they may take longer to dry (wood always dries), or vice versa. The distortions can be considerable, i.e. the entire roof frame will be constantly exposed to different physical forces of tension and pressure. Any experienced roofer will tell you how bad this is and what it entails. Therefore, take more material for making rafters than you plan. If everything goes smoothly, there will be something to use to make the first bench in front of the new house.
Treatment with antiseptics and propylents
And at this stage it is already important to protect the future rafter system from biological destruction. You don’t want your roof to collapse after a couple of years of use, do you? Therefore, be sure to treat the wood for the rafters with fire and bioprotection.
The rafters are usually impregnated with an antiseptic and then treated with a fire retardant on top. You can also alternate this processing several times. If you use universal impregnation, be aware that it usually contains products with different service life. For example, fire protection will end before bio.
But the choice of means for processing today is huge. These include universal protective agents, a variety of fire retardants, and antiseptics. It’s easy to decide: if you are building in a fairly hot and dry area, first of all use fireproofing impregnations, which deprive the wood of its natural flammability. And if your house will be located where the air humidity is high almost all year round, protect it from rotting.
You can, of course, use both drugs - but just do not mix, otherwise the whole material will deteriorate. You just need to choose one product as an impregnation, and the second as a protective surface layer. Just try to dilute everything in the concentration indicated by the manufacturer. But do not treat frozen or damp wood with anything: its fibers simply will not absorb anything.
Video tip on the topic of processing rafters:
Note that a brush or spray when processing rafters gives little result - complete immersion and subsequent drying are much better. Just use a regular container, cover it with film from the inside and make a “bathtub” for future rafters. Moreover, it is advisable to do all this on the ground, as soon as you bring the material to the site, because in the finished rafter system it will be difficult to reach the internal elements of the connections. And they are the most defenseless in terms of moisture penetration. After processing, dry the parts so that all sides are ventilated for at least 24 hours.
Do not forget also that wood, like any natural material, is subject to biological destruction. Therefore, in addition to fire-bio-protection, it is important to consider waterproofing in all places where the rafter system adjoins the brick walls of the house, if any.
Making the correct cuts on the rafters
Now let's move on to practice. First of all, you definitely need to make a convenient template according to which you will make even, identical rafters:
And follow these instructions:
You will have to tinker with the rigid mount:
If we are talking about moving units, then follow this principle:
In practice, everything is actually simple:
As you can see, the eyes are afraid, but the hands do!
How to assemble a rafter system?
Finally, the rafters are ready, and you can start installing them.
Build on the ground or on the roof?
So, in reality, everything is quite simple and somewhat similar to a children's construction set. The easiest and most convenient way is to make trusses directly on the ground, and only then raise them. It is a little more difficult to assemble the rafters directly on the roof, but it is easier to lift them there. This is where you start: if you have the opportunity (a crane, for example) to drag 200 kg of one truss onto the roof - drag it, if not - lift each individual rafter 50 kg using improvised means and do the assembly on the spot.
So, first of all, for convenience, make a template according to which you will assemble the roof trusses, and another template for mounting cuts on the rafters (use plywood). All you have to do is cut out mounting cuts on the rafters, attaching a template, and connect them together at a certain angle. This triangle is called a roof truss.
Attention to strength - rules for increasing length
If the thickness or length of the board is not enough to make a normal rafter leg, extend the rafters. And there are several ways:
- Connect the boards together by folding them with their wide sides and stitching them with nails.
- Lay the boards half the length, resulting in a particularly strong rafter leg that can withstand considerable loads.
- Make an oblique cut at the ends to create a vertical anti-slip stop, and connect with a bolt.
- Lay two overlapping boards a meter long, connecting the rafters with pins or nails.
Also keep in mind when calculating that the roof ridge accounts for about 50% of the load of the entire rafter system. Therefore, always make a ridge beam so that its safety margin is at least 25% greater than originally calculated.
And the most vulnerable parts of the rafter structures are the lower ones, those that rest on the Mauerlat.
Preparing roof trusses
You need to secure the rafters using:
- External straight bracket.
- Metal corner plate.
- Internal metal rod.
You can also connect such rafters with studs - this will even be stronger. To do this, instead of making a cut, we now make a cut into half the tree and connect the rafters with a ledge. Next, drill a hole for a 12-14 mm stud and secure it with nuts and wide washers.
Let's start with a review of proven old-fashioned methods:
If you decide to make roof trusses using a more reliable new technology, you will need the following tool:
Here's how they work:
In details:
When assembling a hanging type truss, you need to connect the upper ends of the rafter legs. To do this, cut the end of each at exactly the same angle at which you are making the roof, connect the beams with cut planes and secure with two nails. Cover the joint with a wooden cover or metal plate.
Another useful master class:
Lifting and installation of finished trusses
Already on the roof, first of all, you need to start by installing those rafters that form the two outer trusses of the gable roof (they are also called gable). To further secure them, install temporary struts. Next, stretch a strong cord between the outermost peaks of the trusses, which will become a level for the intermediate rafters.
Now we lift and place all the remaining trusses at a distance of at least 0.6 meters from each other. Again, if some of your structures turn out to be quite cumbersome, support them with the same temporary supports.
The rest is a matter of technique:
The construction of the roof frame is carried out according to the developed project, which specifies all the necessary parameters, including the type of structure, rafter spacing, cross-section of elements and method of installation of components.
Principles of system calculation
During the operation of the roof, its frame experiences high loads of various types.:
- constant (weight of the rafter system itself and the roofing pie);
- periodic (wind and snow load, weight of a person servicing or repairing a roof or chimney).
To correctly calculate and make a reliable roof, you need to decide on its configuration, choose the type of roofing, and calculate the optimal angle of inclination of the slopes. The degree of complexity of the frame and the dimensions of its elements depend to a certain extent on the parameters of the design load, the main part of which falls on the rafters. It is advisable to choose the dimensions of a wooden rafter, such as cross-section, with some margin of safety.
How to determine the length of the rafters? For calculations, you need to apply the Pythagorean theorem (if the length of the end wall and the height of the ridge are known), or the theorem of sines (if, in addition to the length of the end wall, the angle of inclination of the roof slope is known).
To make rafters, you can use boards or timber. Additional elements that give rigidity to the structure will help build a roof frame designed for high loads.
Determining the pitch of the rafters
To calculate the pitch of the rafters, it is necessary to take into account the weight of the roofing, the angle of inclination of the slopes, wind and snow loads. On average, the pitch (the distance between adjacent legs that form the roof slope) ranges from 70 to 120 cm.
To eliminate the risk of deformation of the rafter legs under high loads, it is recommended to use dry lumber when installing the rafter system. Usually this is a beam or board with a thickness of at least 50 mm. The exact dimensions of the wooden rafters and other elements are determined based on the requirements for structural strength.
The pitch of the rafters depends on the degree of roof slope and the length of the rafter legs. To build a strong roof by covering the large span between the ridge and the top of the wall, the pitch of the rafters should be reduced. For example, for a roof with a slope of 45°, the maximum pitch should be no more than 80 cm. The pitch of the rafters should also be reduced when using heavy roofing materials, which include ceramic tiles, cement-sand tiles, and asbestos-cement slate.
Calculation of the cross-section of rafter system elements
If you have to build a roof with your own hands, you need to do this. You should also pay attention to the characteristics of the material from which the rafter legs are made.
Regulatory documents regulate the load-bearing capacity of wood of various species. If the cross-section of rafters made of timber or boards weakened by cuttings and/or holes for bolted connections is considered, the load-bearing capacity of the wood is calculated with a coefficient of 0.8 from the standard value. It is also necessary to pay attention to the type of wood used for manufacturing - defects reduce its resistance to stress. The cross-section of the rafters is selected taking into account the standard dimensions of lumber. A continuous supporting structure should be made from timber or boards no more than 6.5 m long.
Having calculated the system and determined the dimensions of the rafter legs and crossbars, you need to calculate the total weight of these elements and add the resulting value to the design loads:
- the total volume of lumber required for the roof frame is multiplied by the volumetric weight of the wood;
- the resulting value (the dead weight of the rafters, kg/m2) is added to the calculated load;
- the design design diagram is recalculated using the result obtained above.
Treatment of rafter elements with an antiseptic
In private construction, the construction of a rafter system is most often carried out from lumber, since wood is affordable and allows you to make structures with your own hands without the use of complex tools. Wood material prepared for installation (such as timber, rounded logs) often arrives at the construction site already treated with protective agents under production conditions. But production usually involves boards or timber that are not impregnated with special compounds.
How to treat the rafters before installing the roof frame? Treatment is required to protect the wood from rotting and prevent fire hazards. Treatment with an antiseptic and a fire retardant can be carried out separately. Using a complex fire-bioprotective agent, treatment will take half as much time.
Treatment with an antiseptic or a combined composition should be performed in two steps. It is necessary to saturate the top layer of wood with a special liquid, applying it with a brush or roller. After the first layer has dried, the antiseptic treatment is repeated.
Pitched roof rafters
How to make rafters for a pitched roof? Construction of a rafter system for a single-pitched or gable roof with your own hands requires a careful approach to the manufacture of rafter legs. Dimensions are calculated at the roof design stage. To correctly make these structural elements, it is necessary to use lumber of a section and length regulated by the design.
The degree of complexity of the work largely depends on which structure is chosen for installation. If it is necessary to make layered rafters from boards or timber, each element is adjusted to the installation site when attaching it to the ridge girder and mauerlat. It is important to strictly monitor compliance with the geometry of the entire structure.
It is more convenient to make hanging trusses using a template in order to achieve an exact match of the dimensions of each structure. For this purpose, cutting into boards and assembling trusses is recommended to be done on the ground. Then it is necessary to check the horizontality of the mauerlat or support beams, and the geometric dimensions of the building box. Having eliminated possible shortcomings, you can begin installing roof trusses on the house.
Diagonal rafters
Arranging a hip roof rafter system with your own hands requires the installation of various types of rafters, such as:
- sloped (diagonal beams forming a triangular slope);
- central hip;
- lateral;
- shortened (narozhniki).
The side rafter legs are made of boards and installed similarly to the elements of a conventional pitched roof with a hanging or layered structure. The central hip rafters are layered elements. To make sprigs, bars or boards are used, which are attached to diagonal beams and the mauerlat.
How to make rafters for a hip roof? To properly install this type of roofing structure, you need to accurately calculate the cross-section and angle of inclination of the slant beams. The dimensions of the elements depend on the length of the span being covered. It is important to maintain symmetry when installing diagonal rafter beams, otherwise the roof may deform under load.
Manufacturing rafters to a given size
The use of standardized lumber for the manufacture of various elements of the rafter system makes it possible to optimize construction costs and simplify the calculation and installation of roof components. In particular, if it is necessary to make rafter legs of a certain section and length, a solid beam, its sections or boards can be used.
To make a rigid beam with your own hands, the method of joining the boards is used - they are connected with wide sides and punched in a checkerboard pattern with nails. A long beam of a given section can be made from four or more correctly joined boards - interconnected with a shift of half the length of the board. This beam is highly durable and can be used as a diagonal rafter.
When deciding how to lengthen the rafters, you can use the liner method. In this case, a third one is laid between two boards, protruding to a certain length. To connect the boards, nails driven in a checkerboard pattern are used. It is important not only to carefully align the boards, but also to insert board fragments (inserts) corresponding in thickness to the central board into the empty space between the outer elements. This method allows you to extend the length of standard rafter legs (not hip ones).
Principles of fastening rafters
To ensure the reliability of a rafter system that you build yourself, you need to decide in advance how to attach the rafters to the ridge and to the roof support. If you intend to make a fastening that will prevent deformation of the roof during shrinkage of the building, it is necessary to fasten the rafters together at the top with a bolt with a nut or a hinge plate, and at the bottom to install a special fastening element - a sliding support.
When constructing private houses, the roof is most often made of a gable roof. There are reasons for this. The first is that it is reliable. Copes well with wind and snow loads. Secondly, it is compatible with any roofing covering. The third is relatively inexpensive. The fourth is a simple design that is difficult to spoil. Fifth - she looks attractive. All this, and the fact that a gable roof is built with your own hands without special knowledge, determines its popularity.
The assembled gable roof with your own hands is ready for installation of the roofing covering
Step-by-step installation of a gable roof
As you saw above, there are a lot of rafter systems. Accordingly, each assembly has its own characteristics, but in general the order is the same. It is necessary to talk about the general step: pre-drying and processing of wood. This step is required if you bought fresh lumber rather than dried.
Using raw wood with natural moisture when building a roof will lead to problems: the beams will bend, they will dry out, and the geometry will change. All this will lead to the emergence of stress points and at the slightest sign of overload (lots of snow, strong wind or rain) negative processes will begin. Eliminating them is a complex and expensive undertaking. Therefore, either buy dry wood (no more than 20%, ideally kiln drying 8-12%), or buy the material a couple of months in advance and put it in ventilated stacks. Then treat with the necessary impregnations (against fungal attack and to reduce flammability) and only then use it in the installation of the rafter system.
Lumber should be dried in ventilated stacks. To do this, they are laid with short sections of boards. They are placed a meter from the edges and then every meter. Spacers must be installed under the lower one
We will tell you about the main stages of assembly and how to make a gable roof with your own hands in this section.
Mauerlat
The assembly of the gable roof rafter system begins with the installation of the Mauerlat. It must be positioned strictly horizontally, therefore, before installation, the horizontality of the wall to which it is attached is carefully checked, and if necessary, it is leveled with cement mortar. You can continue work after the solution has gained 50% strength.
Depending on the system, this is a beam with a cross-section of 150*150 mm or a board with dimensions of 50*150 mm. It is attached to the top row of the wall masonry. If the house is wooden, its role is played by the upper crown. If the walls are made of lightweight building blocks - foam concrete or aerated concrete and others - their rigidity is not enough to redistribute the load. In this case, a reinforced reinforced concrete belt is made on top of the last row of masonry, into which embedded fasteners are embedded - wire or pins. A beam or board is then placed on them.
There are several ways to connect walls and mauerlat:
- A smooth rolled wire of large diameter (two ends sticking up) is fixed in the masonry (in a reinforced concrete belt). Holes are then made in the board in the required places into which the wire is threaded. It then curls and bends.
- Studs with a diameter of at least 12 mm are immured in the wall. Holes are made in the Mauerlat for them, a timber/board is inserted) and tightened with nuts and wide washers.
- Having aligned the timber or board along the outer or inner edge of the wall, take a drill with a diameter of 12 mm and make holes for the anchor bolts. They (of the same diameter 12 mm) are hammered in up to the top, then tightened with a wrench.
The distance between the studs (wire) should not be more than 120 cm. A cut-off waterproofing must be installed on the wall (belt) under the Mauerlat. This can be rolled up roofing material or waterproofing material in two layers, or coated with bitumen mastic.
Installation of rafters
There are dozens of types of gable roof truss systems. First of all, you need to choose what yours will look like. Further, in order to make the work easier, a template is made from thin boards for all cuts, notches and other similar parts. To do this, you may need to assemble the first form on the roof, and then make templates using the finished form.
The assembly procedure depends on the type of rafter system. If the rafters are layered, they are installed gradually, assembled from elements directly on the roof. In this case, it is convenient if the ceiling beams are laid and, if possible, the rough flooring of the attic or attic.
In systems with hanging rafters, a truss is assembled on the ground - a ready-made triangle of tie and rafter legs with all the required struts and racks. The required number of farms is assembled immediately. Then they are lifted to the roof, placed vertically there and attached to the Mauerlat.
On the one hand, this is convenient - it’s easier to work on the ground, and with a high assembly speed, the accuracy is high: one truss is not much different from the other, which simplifies the procedure. But lifting prefabricated trusses can be difficult, especially for large buildings. To make this easier, install two inclined boards, one end of which rests on the ground, and the other sticks out slightly above the wall. The trusses are brought closer to this “lift”, one at a time they are installed below, ropes are tied and pulled along the boards onto the roof. If there is no winch or crane, this is the most acceptable method.
Assembling rafters requires certain knowledge: how and in what order to install them, how to mark and make cuts. Watch the video for assembling one of the headstock circuits.
The procedure for assembling the rafter system
That’s it, the gable roof is assembled with your own hands and is ready for installation of roofing material.
The process of installing rafters itself raises enough questions, but there are many ways and it is impossible to tell about them all. Watch one of them in the video. The system was large and was lifted to the roof in parts, and then assembled into a single structure. This is convenient for large houses.
Features of installing the rafter system of a wooden house
The difference between wooden houses is that the log house shrinks, and this leads to a change in the geometry of the rafter system. If the elements are fastened tightly, the roof may fall apart. Therefore, the fastenings are made floating. There are special sliding fasteners, which in this case are used to secure the rafters to the upper crown and to the purlins, if any (see photo).
In order for the rafter to move freely during shrinkage, its long part is fastened strictly parallel to its edge, and placed strictly perpendicular to the support. If necessary, a platform is cut out for it. Mark the fastening so that the hook is in the lowest position or near it. They are attached to special self-tapping screws that are included in the kit (regular ones do not fit). If the installation is carried out on a log, so that the rafter leg does not slip along it, a semicircular hole is cut out in the lower part on which it will rest.
Such fasteners are sold on any construction market, they are called “slipper”. Watch the video to see how to attach the slider to the beam.
Video on assembly and installation of gable roof rafter system
Building a gable roof with your own hands is not easy: there are a lot of subtleties and nuances, there are different methods of fastening and extension. Describing them in words is a thankless task. This is the case when it is better to see. Below we offer you a selection of videos that may be useful to you.
Video report on how a gable roof is made
The house owner's story about the stages of construction. There are interesting technical points that may be useful.
Two types of rafter connections: rigid and sliding
Video about the two most problematic types of connections.
How to determine the angle of rafters
Full video report on the assembly of the rafter system
This film takes just under an hour, but the process is demonstrated from start to finish in great detail. The roof is placed on, but when installed on buildings of another type (except wooden houses) there is no difference.
