The roof of the building is multifunctional. This is not only a kind of decoration for the home, it serves as protection from all kinds of climatic manifestations: snow, hail, rain, wind, and the burning sun. Its surface serves as a drain for water drainage from the basement and walls, contributing to an increase in the service life of the building. Therefore, for any type of construction, the stage of roof installation is so important.
In any design, two main parts are distinguished: bearing (rafter system) and enclosing (directly the roof) .
The most important element of the rafter system is the lathing. A competently made lathing of any roof serves as a reliable rafter support for the roof covering. There are various options for arranging the lathing, which differ in the choice of wood for the rafters and a specific roofing material.
What is a regular pitched roof lathing?
Is it a solid construction of boards or beams, laid on rafter legs, strictly perpendicular to the last . The lathing takes on the main load of the entire roof covering, redistributing it to the rafters.
It also keeps the roofing material in place in windy conditions.
Traditionally, the lathing is made from boards or bars coniferous trees. For this, they usually take bars of 5x5 centimeters, boards from 7 to 15 cm thick 2-3 cm, slats up to 7 centimeters wide. Various materials can be used to lath the roof. Their choice depends on the intended roofing material that was preferred for the roof construction.
It is not recommended to use boards with a width of more than 15 centimeters, because over time, across the fibers, they undergo a warping process.
The material must have such a quality that would ensure that there are no sags and bumps on the roof deck.
This deck must be strong enough not to bend under the weight of the average person. It should also not be unstable, otherwise the connections of the fasteners of individual roof structures may be broken.
The size of the nails used for installation is calculated as follows: the length of one nail must be at least twice the thickness of the board to be nailed.
It is advisable to carry out all work on the final installation of the roof in dry, clear weather, without rain, because the lathing must be dry during installation work. All lumber intended for its manufacture is treated with antiseptic agents.
The lathing can be:
Both types are used exclusively for a specific roofing material. For example, under shingles, you can use a strictly continuous roof lathing. For roofing materials that have their own rigidity, such as metal profiles, tiles, slate, a thinned lathing is quite enough. The installation of the battens can be done in two-layer and one-layer versions.
Two-layer crate, which is clear from the name, has two layers. The lower one is represented by supporting beams fixed on the rafter legs, located parallel to the ridge, the distance between which is from 0.5 to one meter.
The top layer is mounted from the ridge to the overhang, securely attached to the lower part beam: it is a grooved or edged board, OSB-boards, tes and plywood. It is possible to lay the top layer diagonally, with a 45 ° slope to the timber and boards of the bottom layer.
Usually, the two-layer installation method is used in cases where material savings are required, and there is too much step between the rafter legs. In addition, with the initial, first layer of double lathing, it will be possible to level the not too well-made rafter frame.
The hydro-barrier is designed to protect the insulation of the roof with the attic floor from moisture ingress. A large amount of it is in the atmosphere, and as a result of sharp changes in t, forms condensate drops on the inner surface of the roof covering. A simple roofing felt or a microperforated roofing film can act as a waterproofing roof.
Since this material does not have its own rigidity, roofing glassine, or roofing felt, is most often spread on a continuous crate. It does not make much difference how to arrange the material, horizontally or vertically, the main thing to remember is that the canvases are mounted with an overlap of at least 10 centimeters.
Horizontal installation from bottom to top. For a sparse lathing, a special under-roofing film is often used. It is pulled on top of the rafters, with the use of further installation of the counter-lattice.
They begin to fix the film with a stapler to the rafters, starting from the very bottom of the ramp.
Important! Roofing foil has two different sides. The top can be easily identified by the manufacturer's logo printed on it. It should face space, into the sky, and the lower one, without inscriptions, is directed towards the inside of the building. The fact is that the film has different properties in different directions.
The next rows of the film are laid on the previous ones, with an overlap of 15 to 20 centimeters.On both sides of the film there are marks located along its edges in the form of a strip, making it easier to work on its cutting and installation.
Counter-lattice bars prepared in advance are nailed onto the stretched film from above. The width of the rafter leg and the width of the bar must be equal, the length of the bar is equal to the width of the roofing film.
The block should be between 3 and 5 centimeters high: this value provides an adequate air gap between the roofing material and the water barrier.
All work should be carried out alternately, layer by layer : first a row of film, then a counter-lath, then a roof lath. Carefully moving along the already installed wooden crate, you can step by step proceed to the device of each subsequent row.
For the reliability of the structure, the bearing capacity of each part of the building plays an essential role, including the thickness lathing. It is directly related to the size and properties of the material, with the step size of the pivot points. In order to guarantee the required bearing capacity of the lathing, it is necessary to correctly determine its material (metal profile, board, timber), its parameters and the pitch of the lathing.
The required thickness of the timber or board for each specific case is calculated using a special formula.
It is possible to simplify the solution of the problem: between the rafters you need to nail a board, and try to stand on it. If no significant deflection is observed, then the choice of its size is made correctly.
For sheet materials a solid lathing is required, which is in fact a unique design.
They make it from a thick (at least 2.
5 cm) edged board with a width of not more than 14 cm. Too wide boards can begin to warp over time. The material used must be well dried.
In the case when the inter-rafter distance is more than one meter, and the acquired board noticeably bends under the weight of the body, it is better to make a two-layer lathing. Bars thicker than traditional ones (5x5 cm) will be required: they must be nailed, parallel to the ridge, to the rafter legs.
This will avoid deflection of the upper layer of the boards, which will spread diagonally on the laid beams or from the ridge to the overhang. Then the made continuous crate is covered with an overlap of ten centimeters with glassine or roofing felt.
Then the direct installation of the roofing sheets themselves is carried out. The lathing made in this way is very reliable and can be used for various materials. Its versatility allows you to successfully combine it with corrugated board, corrugated and flat asbestos-cement sheets, bituminous tiles, metal tiles, folded paintings.
On metal roofing, it can significantly reduce rain noise.
For metal tiles, you can make a crate in two different ways. You can arrange a sparse crate, which is adjusted to the size of the coverage wave, or the solid one described above. The latter method is well detailed, but there is little emphasis. According to the technology, the lowest row of metal tiles should be raised to the height of one wave.
Therefore, a board must be nailed to the edge of the slope, the thickness of which is equal to the size of the wave of the tile. Now let's look at the first option.
Single-layer sparse crate is made of edged board 3x10 centimeters, with a rafter pitch from 0.8 up to 1 meter. If the board is thinner (2.
5x10), then the pitch is reduced to 0.8 meters. Are there any peculiarities of the installation? It is first required to make a hydro-barrier from an anti-condensate micro-perforated film. Above has already been given a description of its construction. The sheathing board, the first from the eaves, must be one wave height higher than the boards in the main covering.
It is nailed under the hydro-barrier, to the very edge of the cornice. The subsequent one is nailed to the counter-batten in such a way that between the edge of the cornice board (the first) and the middle of the second there is a distance similar to the width of the tile wave. The remaining boards are nailed at a distance corresponding to the wave step of the selected metal tile. The nails are hammered in strictly in pairs, at the edge of the boards: the caps must be sunk into the wood. If short boards are used for the construction of the lathing, then their joints should have a checkerboard pattern.
Important! At the intersections and junction of slopes (ribs, ventilation ducts, ridge, gutters, chimneys) and along the overhangs of the cornices, a continuous crate is desirable. Otherwise, when installing additional elements, the self-tapping screws of the roofing will end up in the void.
A seam roof is successfully equipped with a continuous or sparse crate. If the roof has a complex geometry, or the roof has a slope of 3-14 °, it is advisable to use a solid batten. In others, it is quite acceptable to make it sparse, saving on materials.
We have already described how to make a solid crate. The features of the sparse design for folded paintings will be discussed below.
It is extremely important to properly calculate the required batten pitch for this type of coverage. Otherwise, it is quite possible that noticeable deflections of the steel sheets will appear, as a result of which the roof will become wavy, and not flat, as it should be. Usually, in such cases, to install the crate, they take a board measuring 3.
2 * 10 cm or a five-centimeter (5 * 5) bar. The board or timber is fixed from the eaves to the ridge at a distance of approximately 30-40 cm. On the rafters, even before the installation of the battens, an anti-condensation film should be laid (playing the role of a hydro-barrier), as well as a counter-lattice should be nailed.
The crate should be made from the cornice. The first board is nailed along its edge, which should cover the end of the cornice filing, then in increments of up to 40 centimeters to the ridge itself.
A solid lathing (0.6 m from the edge) is arranged at the points of installation of valleys and cornices, in the places of adjoining parts of the building that protrude. The very last ones to install are additional boards, to which transition bridges, snow holders and so on will later be attached.
The complete absence of irregularities, indentations and protrusions on the crate is a prerequisite. The bottom board of the eaves, ribs and ridge is recommended to be made straight.
Since a metal sheet adjoins the crate, the tree must be painted or treated with antiseptic compounds. The service life of the structure also increases when dried wood is treated with drying oil.
The structure of slate lathing usually consists of wooden beams perpendicular to the rafters. The distance between them depends on the size of the used roofing material. For standard sheets of asbestos cement slate (1.
2 * 0.68 m), it is about half a meter, while the beam itself should have a cross section of 5 by 5 centimeters. When using a unified version of this slate (1.75 x1.125 m), it must be kept within 0.
8 meters, and the dimensions of the timber are 7.5x7.5 cm.
Each slate sheet must have a support of at least three beams. For this reason, the curtain rail must be 6 mm thicker than others, or it must be lifted by means of shims.
Even bars are made three millimeters higher than the odd ones.
In the case when four battens are supposed to be laid under the sheet, they should have three different types of thickness: main, 2 mm more, and 4 mm more. This difference is ensured by the use of special spacers for the beams (pieces of fiberboard, roofing felt, roofing felt, etc.) or pieces of lumber of different sizes. This design provides a tight overlap of the roofing material, as well as a uniform load on the slate sheets.
Near the ridge, overhangs and grooves, the flooring of wood should be continuous. The listed principles of this design may well be used for the construction of the lathing for ondulin, having previously calculated the necessary step of the board or bar for a specific sheet.
The device of the lathing for ceramic, polymer-cement and cement-sand tiles in the work of roofers is considered the most difficult. For ceramic tiles, a sparse sheathing structure with five-centimeter bars is required. For cement-sand, a more massive timber is needed, 6x6 cm.
The event begins with a hydro-barrier device from a special film, then a counter-lattice is made. Then comes the most crucial moment.
It is extremely important to calculate as accurately as possible the size of the steps between the battens of the sheathing, and to carry them out in strict accordance with the calculations made. Ideal tiled roofing requires a whole number of tiles, both in the transverse and longitudinal direction.For a tile, you will need to calculate its covering value, since this indicator should be equal to the lathing step.
It can be 16-40 cm, depending on the type of profile and its manufacturer. Most often this figure is 30-33 centimeters.
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