The rafter system of a gable roof is considered one of the simplest in purely structural terms. It consists of only a few elements, the number of which decreases or increases due to the size of the roof itself. But despite its apparent simplicity, the process of erecting a gable roof requires knowledge of some nuances that affect the quality of the final result.
Rafter system for a gable roof
From the name it becomes clear that the roof structure consists of two slopes with rectangular shape in a plane. More often, the slopes have the same dimensions, but there are so-called asymmetrical designs in which the slopes differ in size from each other.
In this case, the slopes are installed to each other at a certain angle, which is called inclination. The line of contact is ridge beam, which is part rafter system. Simply called the ridge, it is the highest point of the roof.
The side planes formed by the slopes are called pediments. They have triangular shape. After constructing the roof, the sidewalls are lined with sheet or panel materials: plywood, OSB, even boards, etc.
The basis of the structures of the slopes are the rafter legs, also known as rafters. They are made either from lumber (timbers, boards) or from a steel profile (angle, channel). Wood is used in private house construction. It’s easier to work with, plus the lumber is cheaper.
The construction of a gable roof rafter system is not only about rafters. Besides them there are several more mandatory elements. The photo below shows all the elements of a gable roof. Let's label them.
Each roof element has its own purpose
Elements of a gable roof rafter system
Mauerlat. Essentially, this is a beam on which the rafters rest. Its purpose is to evenly distribute the loads from rafter legs on the walls of the house. If the Mauerlat is not used, then the rafters will put pressure on the walls pointwise, that is, large stresses will arise at the installation sites, which will lead to cracking of the walls.
Rafters installed at an angle.
Horse, aka ridge beam or purlin. Its task is to form the joining point of the rafter legs. Ridge beam is an optional element of a gable roof. There are designs in which it is not installed. But more on that below.
Puffs. They are not always used, but only for hanging rafters ah or, if the rafter system is installed on a wide house.
Floor beams, which form the ceiling in the room and the floor in the attic.
One of the floor beams, called let's lie down. It additionally serves as a base for the support posts that support the rafters. Not always used.
Support posts, they are also the headstocks that support the rafter legs. They are installed only if the span of the house is at least 6 m.
Struts, they are also diagonal supports. They are used only if the support posts cannot ensure the overall reliability of the rafter system.
There is one more element that is clearly visible in the photo below. These are support posts for the ridge girder. They are installed if the structure of the rafter system is heavy. That is, the entire structure is assembled under heavy roofing material, for example, ceramic tiles.
Layered rafters with support posts under the ridge girder
You might be interested! Warm roof– this is an important detail when building an energy-efficient house. From the article at the following link you can find out.
The roof rafter system (gable) can be assembled from layered or hanging rafters.
They got their name because their lower ends rest on the walls of the house, and their upper ends rest on the ridge girder. Wherein rafter elements are subjected to loads that bend them. The design is reliable, durable, with high load-bearing capacity.
The photo above just shows a layered rafter system. It is clearly visible that the legs rest on the ridge at the top. In this case, there are two types of fastening of the rafters themselves in the upper part:
fastening is done to the ridge:
fastening is done to each other with emphasis on the ridge (photo above).
It is necessary to immediately indicate that this type rafter system can be used if the distance between the walls of the house does not exceed 12 m. Because the rafters rest with their lower ends on the walls, and their upper ends only with each other (there is no ridge girder in the design). Hence the low load-bearing capacity with a large spread.
Hanging roof rafters have one purely design drawback - a large support load on the walls of the house. To reduce it, strings are installed between the legs to form a rigid triangle. Often the functions of puffs are performed load-bearing beams ceilings
If it is necessary to strengthen the hanging rafters, racks and struts are installed under them.
Hanging rafters of a gable roof
Two types of rafter systems determine two types of assembly technology. Let's look at each one separately.
There is a certain sequence for assembling layered rafters.
Two outer support posts are installed under the ridge beam. They will not only support the timber, but will also be the elements that form the gables of the building. They are attached at the bottom to the Mauerlat. In this case, they are strictly aligned vertically, and the upper ends are in the same horizontal plane. To do this, stretch a strong thread between the posts and check it with a level to ensure it is horizontal. If there are deviations, then one of the supports (low) is raised using wooden supports.
Intermediate support posts are mounted along a horizontally stretched thread in increments of 2-2.5 m. To prevent the beams of the posts from moving, they are supported with temporary fasteners: supports or tie-downs.
A ridge beam is placed on the racks, which is also attached to them.
Produced in pairs installation of gable roof rafters. Installation can begin from any side. The fastening is carried out immediately to the Mauerlat and to the ridge. The main thing is to maintain the distance between the legs, which is determined depending on the gravity and load-bearing capacity roofing material. Usually this parameter is indicated in the house design.
If necessary, intermediate support posts and struts are installed.
Installing rafters on a ridge along a tensioned thread
The technology for installing hanging rafters is different. To do this, the entire structure, assembled from two rafters and a tie, is assembled on the ground. That is, roof trusses are prepared in the required quantity, which are then lifted onto the roof. Sometimes craftsmen assemble roof trusses. They assembled one, installed it, and assembled the next one.
It should be noted that such farms have a significant mass. Lifting them manually is difficult and dangerous, so they use the services of a crane. And this increases the cost of construction.
Hanging roof trusses assembled on the ground
The most difficult thing is to display the farms. All of them are installed at the installation site with a planned step, where they are temporarily secured with jibs and supports. Then a thread is stretched between the outer trusses. It must be positioned so that, firstly, it is stretched strictly along the horizon, and secondly, along a structure that is higher than the rest.
All that remains is to raise the rafter structures that are below the tension level. And the last thing is the installation of the sheathing, which will secure all the trusses into one rafter system. Please note that in the lower part of the rafters will be fixed to the Mauerlat.
This might interest you! When the installation of the rafter system is completed, it’s time to roofing works. From the article at the following link you can find out.
length of rafter legs;
step of their installation;
cross-section of the lumber used.
With length, everything is simple; for this you will have to use the Pythagorean theorem, which is based on the formula: c 2 =a 2 +b 2, where c is the hypotenuse of the triangle (this is the rafters), a and b are the legs. The latter are the height of the roof and half the width of the house. All parameters can be easily measured.
The length of the rafter is l 2 +H 2
The installation pitch is more difficult, because much will depend on the weight of the roofing material and the loads from natural precipitation. The greater both loads, the smaller the installation step. But, as practice shows, this parameter varies from 60 cm to 2 m. The latter indicator is used if corrugated sheeting with large corrugation parameters, for example, H75, is used as a roofing material.
As for the cross-section of the rafter legs, here, as in the case of the installation step, the loads are taken into account, as well as the length of the legs and the step of their installation. Here the relationship is as follows: the greater the load, pitch and length, the larger the cross-section.
In the video, the installation process of the rafter system:
And one moment. Rafters for a gable roof are laid at a certain angle (indicated by the letter “a” in the photo). The slope is selected based on the choice of roofing material. That is, some coatings cannot be laid on roofs if the angle of inclination is less than the required one. Here are some ratios:
the minimum angle of inclination of the rafter system for slate is 22°;
for corrugated sheets – 12°;
for metal tiles – 14°;
soft tiles – 15°.
Ratio of roof slope to type of roofing material
On our website you can find contacts construction companies who offer turnkey roof design and repair services. You can communicate directly with representatives by visiting the “Low-Rise Country” exhibition of houses.
Gable roofs are traditional designs. But from the article it becomes clear that there are two rafter systems that form the basis for the construction of roofs. The one that fits the size of the house is selected. The loads pressing on them are also taken into account as a selection criterion. Therefore, it is important to correctly correlate everything, taking into account the nuances of construction processes.
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.
But then be prepared for the following disadvantages:
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:
Rafters in the construction world on in simple language It is customary to divide 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 the lining of 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:
Complex roofing structures with multiple elements it is better to entrust the calculation to a professional, but with a small roof of a private house you can handle it. 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:
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 compile detailed project, and better 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.
The angle of inclination of a gable roof is made from 5° to 90°. But the most proven and standard option– 35°-40°, where loads are most rationally distributed and building materials are consumed.
Straight slopes are built when under the roof in the future there will only be non-residential attic, main function which is ventilation and heat exchange regulation. But when the under-roof space is planned for residential or attic space, they initially plan a so-called broken line 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°.
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:
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 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.
The more racks, struts and contractions, the more durability and stability the entire rafter system has.
If you have any suspicions or even an exact estimate that simple design the roof will not withstand future loads, make it additional elements gain. 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°.
And the run is horizontal beam, which is located parallel to the ridge and is fixed on vertical posts. More details in the video:
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:
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, and clogged drainage system, and the gradual destruction of the entire roof. Decide for yourself!
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 like 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.
So, if you have decided on future loads, it’s time to choose suitable material. The following are usually used for making rafters:
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 some of constituent elements you will have to make glued ones. 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 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 special device to measure 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 from regular board It is most convenient to splice rafters along the length:
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:
The beam is more durable, but the disadvantage is that it has a lot of weight and you have to make cuts in the fastening areas. 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:
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 any individual elements you had to purchase roofs 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 strength stretching 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.
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, know that it usually contains products with for different periods services. For example, fire protection will end before bio.
But the choice of means for processing today is huge. These are also universal protective equipment, and 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 is located where the air humidity is almost high all year round– protect 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 a finished rafter system it will be difficult to reach internal elements 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, 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.
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're talking about about moving parts, then follow this principle:
In practice, everything is actually simple:
As you can see, the eyes are afraid, but the hands do!
Finally, the rafters are ready, and you can start installing them.
So, in reality everything is quite simple and somewhat similar to the children's designer. 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.
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:
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 truss structures- lower ones, those that rest on the Mauerlat.
You need to secure the rafters using:
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:
Here's how they work: 
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:
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:
21.02.2017 1 CommentRafter system gable roof- a simple design that even a novice developer can build with his own hands. 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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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 have corrosion protection.
To install a gable roof rafter system, you will need the following set of tools:
Keep all tools on the roof in a tool bag for safety reasons.
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
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
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 m2 roofing, lathing. 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 table values regulatory documents SNiP, 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.
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:
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 get on the wall and the foundation is not poured.
The rafter system of a gable roof consists of the following elements:
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:
For it, take timber 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. WITH outside brick the walls and mauerlat. 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.
The installation of a gable roof rafter system with your own hands is carried out in the following order:
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:
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:
Lathing is installed along the roof rafters. It serves to distribute the load from roofing material and snow onto the rafters. Acting air gap between the roof and the rafter system.
The design of the sheathing depends on the roofing material used:
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.
Arranged for protection from precipitation, play aesthetic role. Eaves overhangs are arranged tightly without gaps. The final stage on roofing.
Diagram of the eaves overhang of a gable roof
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. Gables support rafters and enclose attic space. They protect from wind and precipitation and provide stability to the roof.
IN wooden buildings the pediment is made frame. 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, they make a additional frame according to window size. 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, with inside under finishing material nail a vapor-proof film or a vapor-proof membrane.
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Rafter system - powerful roof frame for holding roofing and other elements.
How well is the roof frame constructed? The strength of the roof as a whole depends.
Otherwise, its functionality and ability to protect the building from external influences and provide warmth in the house.
Therefore, you need to correctly approach the choice of rafter systems and correctly draw up a rafter plan.
You can read how to calculate the rafter system.
Depending on the purpose of the room, the size of the gable roof, the structure of the rafter system is classified as follows: hanging system and layered.
Hanging rafter system for a gable roof has support only on load-bearing external walls building.
Depending on the width of the span and the design of the roof, the installation of hanging systems has features.
It is advisable to erect a hanging structure for buildings where the distance from one wall to the opposite does not exceed 6 meters. The frame has the shape of a triangle.
To strengthen bearing capacity faces of the frame triangle, use several methods:
Using these methods, it is possible to distribute the load throughout the entire structure.
Strengthening the frame triangle
When arranging the frame, you should pay attention to some points:
CAREFULLY!
Particular attention should be paid to fastening the elements, since the attic experiences loads both outside and inside.
In addition, the rafter system of a gable roof with an attic is equipped with insulation, which increases the load.
Rafter frame for mansard roofs
When spanning more than 6.5 meters, installing a hanging system requires installing more fastening elements to prevent sagging of the tie, which is caused by its own weight.
Points to consider:
When installing the system hanging type sometimes you can do without installing a Mauerlat and limit yourself to installing boards on film. In addition, the hanging system is characterized by the absence of complex components, which facilitates the work on arranging the roof frame.
Hanging system
The difference between a layered structure and a hanging one is that the structure has additional support points inside the room. Required condition installation of a layered system is the installation of a Mauerlat.
The system design provides for the installation of both spacer and non-spacer frames.
A non-thrust frame should be installed in houses with log walls. When installing rafters, their bases must be attached to the Mauerlat.
Options for attaching the system base to the Mauerlat:
When attaching rafter legs without connecting them at the ridge part should Special attention pay attention to the accuracy of calculations.
Even for minor discrepancies in the scheme, expansion pressure will act on the walls of the building, which may lead to the destruction of walls.
Spaceless frame
To strengthen the structure and give it stability, Screws are mounted to the pillars of the structure. You should use timber of the same cross-section as for the rafters. To increase strength, the screeds are nailed on both sides of the beam.
The same fastening option is effective for firmly fixing the ridge element, which prevents the roof from moving horizontally.
Frame with contractions
The struts enhance the load-bearing capacity of the wooden frame and ensure the strength of the rafter board.
An important requirement when installing a strut is a correctly measured cutting angle, which makes it possible for the strut to fit tightly to the elements being connected.
ATTENTION!
If, with a layered system, the support part is located in the center of the base of the frame, then the strut is attached at an angle of 45° to the horizontal line; if the support is closer to one of the load-bearing walls, then the attachment angle can be different: from 45° to 53°.
It is advisable to erect a frame with struts in places where there is a possibility of the foundation landing, or in wooden buildings, where slight shrinkage of the walls is acceptable.
Frame with struts
When there are two supports in the form of internal walls, then when arranging the rafter legs, beams are placed under them. If the beams are not installed, then a post resting on the internal support is nailed to the base of the rafters.
Rafter beams are installed on load-bearing supports. On the supports inside the room, beds are installed, onto which the load from the rafter beams from the racks falls. The rafters are cut so that they fit snugly against each other and secured.
With this design, the ridge girder is not installed.
To ensure that the structure is non-thrust, tie downs are attached.
The stability of the structure is ensured with the help of racks, which are installed horizontally from the inner base to the rafter leg, and joints, - wooden beams, which connect the bases of the racks diagonally.
If the structure is spacer, then a beam is attached above the purlin, connecting the frame legs - a crossbar.
Layered system
Types of rafter systems
Before installing the rafter system under the attic, it is necessary to correctly calculate the roof load and take into account other factors, which may affect its functionality. All wooden elements must be treated with antiseptics.
Installation of the rafter system is carried out in stages:
After installing the frame, they lay it on it vapor barrier film, install , elements and covering material.
Mansard roof installation
The attic of a gable roof has the simplest hanging system.
For attic floor It is advisable to make ready-made trusses on the ground, and then lift them to the roof, having previously installed the Mauerlat.
Trusses consist of rafter legs, firmly secured with a tie at the lower base. You can additionally use struts or headstocks.
Securing the tie rods to the rafters is of great importance. It is recommended to install the tie rods so that their beams are located half a meter behind the wall line, then there will be no need to additionally install an overhang.
You can read how to make rafters yourself.
The trusses are secured using upper and lower purlins.
Rafter system for the attic
When arranging the frame of a gable roof, the following elements are used:
The combination of several elements (rafters, racks, braces) in one plane is called a truss.
Rafter system of a gable roof, drawings and photos below:
Drawing of rafter system elements
Reliable fastening of structural components ensures the strength and durability of the structure and helps to increase its service life.
The strength of the base of a gable roof depends not only on proper fastening.
It also consists of the correct calculation of all frame elements, from a verified determination of the type of structure at the project stage.
Rafters for a gable roof are connected to different structural elements.
Depending on the span, the elements are attached:
