To protect the interior space of a house, a variety of types of roofs can be used. They look very nice, for example, four-slope, hip, multi-tongue. However, most often the owners of private houses erect ordinary gable roofs. This form of roof is popular primarily because of the ease of assembly, but also because of the reliability. In addition, under the roof of this variety there is enough space for a large attic or attic.
Design Features
Installation of the gable roof truss system, like any other, is carried out on the Mauerlat. Also, the design of such a roof may include:
- rafters;
- racks, runs, lying down;
- skate;
- sheathing.
To protect the truss system from moisture, hydro and vapor barriers are used. They are usually installed on top of the insulation. This material is necessary to protect the attic or attic from the cold. Of course, at the final stage, the frame of the house is sheathed with roofing material.
Mauerlat for a gable roof: installation features
This structural element of the roof frame is usually assembled from a very thick timber (section 150-200 mm). After all, it is he who serves as the main support of the roof. Mauerlat is laid on top of the walls of the house. If the latter are assembled from gas or foam concrete blocks, a reinforced concrete belt is preliminarily equipped. To fix the Mauerlat, anchor bolts are poured into it. Under a gable roof, the Mauerlat usually fits only on two walls - parallel long ones. This element is not used on cobbled, log and panel houses. In this case, the upper crown or strapping serves as a Mauerlat.
Roof rafters
This is one of the most important elements of the roof. The truss system is assembled in most cases using a material such as a beam of 100100 mm or 150150 mm. Also, a board 100150 mm can be used under it. Before erecting the rafter system, the material is cut in such a way that at the top the legs adjoin each other or to the ridge as tightly as possible (cut at a certain angle). Also sometimes choose landing nests in the lower part of the legs. This allows you to build a more reliable roof.
Wooden rafters can be attached to the Mauerlat, upper crown or strapping in different ways. Sometimes they are fixed with a “knot” for three nails and a thick wire. But more often, nevertheless, the legs are attached to galvanized steel corners on both sides. This greatly facilitatesassembly. At the top, the rafters are attached to each other using metal jumpers or to the ridge on the corners.
On wooden chopped buildings, timber (100100 mm, 150150 mm or 100150 mm) is fixed by means of special additional elements - “sled”. This ensures the mobility of the rafters. The use of such fasteners is justified primarily by the fact that when drying out, the walls of houses are able to shrink. Therefore, it is impossible to rigidly fasten the truss system (on nails or corners) in this case. Otherwise, she may simply be led.
Gable roof rafters: varieties
Sometimes the sloping beam of the roof frame can only be attached below - to the Mauerlat and above - to each other or to the ridge run. Such rafters are called hanging. But another type of frame is often used. In this case, an additional support is installed under the legs (along the entire length) in the middle of the slope. As a result, the roof is "broken". Such gable roofs are called attic, and their rafters are called layered. This is the most practical type of roof of a country house. The distance between the rafters - both layered and hanging - is determined based on the thickness of the selected timber, the length of the slopes, etc. Usually the step is 60-80 cm.
Sub-rafter frame system
On large-area houses, in addition to the Mauerlat, the sloping roof beam can be supported by girders, racks and beds. The first are installed horizontally, the second - vertically. Lying is called a beam laid along the floor beams. They are attached to it with a certain step along the entire length of the rack roof. Next on themskating run is installed. For this element, a bar 100x150 mm is usually used.
Skate run
Installation of a gable roof truss system using this element is done quite often. And this despite the fact that the roof in this case is more expensive. The fact is that the roof frame with a run is more reliable and better resists various kinds of loads.
This element must be installed in compliance with all required technologies. The accuracy of the geometry of the roof depends on how carefully it will be mounted. When assembling a roof with a ridge run, first install the extreme racks (along the gables). Next, an inelastic cord is pulled between them and leveled. Then, focusing on it, install all intermediate racks. In this case, the ridge run attached to them in the future will be located absolutely horizontally.
Crate
This is also a very important structural element of any roof. The board for the crate is usually chosen quite thick. Depending on the roofing material used, a 2.5-5 cm option can be used. Do not take a too narrow or wide rail for the crate. In the first case, the boards can warp, in the second - crack. The optimal width of the material for the crate is 20 cm.
The step between the boards, as well as their thickness, depends on the type of cladding chosen. Such a sparse crate is suitable only for rigid sheets. Under the roofing material and very thin metal, a solid one is mounted. For such a crate, it is usually not a board that is used, but sheets of thick plywood or OSB.
Heat-insulating layer and waterproofing
The design of a gable roof is such that absolutely any modern material can be used to protect its internal space from the cold. Most often, mineral wool is used to insulate the attic or attic. Sometimes polystyrene foam is also used. In very rare cases, roofs are insulated by spraying polyurethane foam.
As a support for mineral wool and polystyrene, a wire is pulled from the side of the attic. The sheets or plates themselves are installed directly between the rafters. Mineral wool is mounted simply by surprise. The gaps between the polystyrene foam sheets and the timber are sealed with special mounting foam and glued with adhesive tape. Steam and water insulators are fixed with a slight sag (2 cm) in a horizontal position at the final stage of assembling the truss system.
Roofing material
Metal tile, slate, ondulin, profiled sheet can be used for roof sheathing. Sometimes roofs are equipped with roofing material. The roofs of expensive large cottages are often covered with clay tiles. In general, there are simply a huge number of types of roofing materials. Metal sheets are fixed on the slopes by means of self-tapping screws. The roofing material is glued to a continuous crate using bituminous mastic. She also coats the seams. Clay tiles are also attached to the roof with self-tapping screws through the holes in it.
Rules for the selection of lumber
Gable roof truss installation should be done using only the highest quality lumber. When buying them, you should follow certain recommendations. Lumber intended for assembling the roof frame must be dry. The permissible percentage of its humidity is 18%. Usually in woodworking workshops they sell material that does not meet this requirement. Therefore, before assembling the roof, it is advisable to dry the tree under a canopy for at least six months.
You can build a roof immediately after buying timber and boards only if they are made from a "winter" forest. The fact is that in the cold season, sap flow stops in tree trunks. As a result, lumber made from such logs does not initially contain too much water.
When choosing boards and timber, in addition to their moisture content, it is worth paying attention to their quality, of course. The fewer knots in the lumber, the better. As for the type of wood, pine is most often used for assembling roofs.
Another parameter to consider when buying timber and boards is their geometry. The materials must be perfectly straight. It is not allowed to use “twisted” boards or timber for assembling the roof. Also, the material should not have too many cracks.
Protection of the truss system
The construction of a gable roof is a procedure that involves the use, among other things, of various kinds of materials intended forto prevent wetting of the beam and water ingress into the under-roof space. As a waterproofing agent, technical polyethylene film is most often used. Sometimes a special membrane is also used. Such material is much more expensive than polyethylene, but it also lasts much longer. Films of this variety can retain moisture coming from the outside, and at the same time let vapors coming from inside the house pass through them. This ensures that the heat insulator and lumber inside the roofing "pie" always remain dry. Which, of course, significantly extends the life of the roof itself.
Under the sheathing material inside the attic or attic, a special film is mounted, which is called vapor barrier. Sometimes special foil sheets can also be used instead. They cost more than film, but, among other things, they contribute to the preservation of heat in the attic or attic, creating a “thermos effect”.
After the installation of the gable roof truss system is completed, proceed to its sheathing. Roofing material should be chosen carefully. Indeed, the reliability of the roof directly depends on its quality. Therefore, when buying, first of all, you should pay attention to the reputation of both the manufacturer and the supplier.
Roof calculation: slope angle
Of course, in order for the roof to turn out to be absolutely symmetrical and as durable as possible, a detailed project must be drawn up before assembling it. This document should be accompanied by drawings of the roof in frontal and profile projection, andalso plan (top view).
The gable shape of the roof is also good because it is completely easy to calculate it. To do this, you need to determine the angle of inclination of the rafters, the cross section of the material and its quantity. The first parameter is determined based on what roofing material is supposed to be used for sheathing. So, for example, for a metal tile the minimum indicator is 12 gr. Ruberoid can be used on roofs with slopes up to 15 degrees. In this case, four layers are applied. When pasting the roof at 40 degrees, 3 layers are laid, and over 45 gr. - two. Ceramic tiles can be used on roofs with slope angles from 22 to 45 degrees.
If the roof is too flat, it can bend or even collapse under the weight of the snow cover. Very steep slopes are subject to strong wind loads. Therefore, when choosing the angle of inclination, one should take into account the climatic features of a particular area. That is, the maximum wind and snow load in your region.
Which angle of inclination to choose when building a house with a gable roof in a particular region of the country, you can find out using information from special tables. But in most regions of Russia, 35-45 grams is considered the best indicator. Mansard gable roofs are equipped in such a way that the angle of inclination of the upper rafters with respect to the horizon does not exceed 30 degrees.
Calculation of materials
Thus, it is not difficult to determine the optimal angle of inclination of the slopes. Once this settingis selected, you can proceed to the calculation of the roof frame. The first step is to calculate the required length of the rafters. Knowing the angle and length of the short wall of the house, it will not be difficult to perform this operation using the appropriate trigonometric function. To the resulting figure, add 20-40 cm to the overhang of the cornice.
Knowing the length and distance between the rafters (and their number), it is easy to determine how much timber should be purchased. To calculate the boards of the crate, you need to know the step between them. In this case, it should be borne in mind that on the cornice and at the ridge, two rows of material are stuffed with solid material. To calculate the number of sheets of heat insulator, film and sheets for sheathing, you just need to determine the total area of \u200b\u200bthe slopes. To the resulting figure you need to add 10% for losses.
How much will the roof cost
In addition to the drawings, the cost estimate of materials must be attached to the project. By calculating their required number, you can calculate the total cost of the roof. For 2016, the approximate cost of materials for the roof is:
- pine beam 150x100 mm (for rafters) - 612-700 rubles/pc. (6 m);
- pine board 25x200x6000 mm (for lathing) - about 500-550 rubles/piece;
- beam 200x200 mm (Mauerlat for a gable roof) - about 1200-1500 rubles / piece. (6 m);
- technical polyethylene film (80 microns) - 990-1,000 rubles. per roll (3x10 m);
- vapor barrier - 400-500 rubles. per roll;
- mineralcotton wool "Ursa" - 1,500 rubles. (package 2x9000x1200x50).
From roofing materials, the cheapest option is roofing material. A roll costs about 350-400 rubles. But most often, the owners of country houses cover the roofs with metal tiles. The cost of this material is about 300 rubles. per sheet.
What tools are needed
To install the rafter system, you will need a hacksaw (or electric saw), a screwdriver and a hammer. For sheathing the roof with metal sheets, among other things, you will need to prepare sharp metal scissors. It is impossible to cut material with a polymer coating with a grinder, otherwise the upper, protective layer of the sheets may be damaged. As a result, the roof sheathing will begin to rust very quickly.
If it is decided to cover the roof with roofing material, it is worth preparing a barrel for melting bitumen and a stick with a thick rag wound around it. You will also need several buckets.
Of course, for the installation of the roof you will need a reliable ladder, and possibly walkways knocked down from the boards. To install metal tiles, it is also desirable to prepare shoes with soft, but not slippery soles.
