Roof batten - selection, design and installation

The rafter system is a complex device consisting of a set of interrelated elements, which provides support for roof slopes. This is perhaps the most difficult in the design and installation of a structural unit of any structure. To make the framework durable, reliable and able to withstand intense loads, it is necessary to correctly calculate and determine the number, size and mutual distance between its elements. The lathing of the roof, despite its external simplicity, plays an important role, distributing the weight of the roofing pie between the supporting supports. In this article we will tell you what a crate is, as well as how it is done with your own hands.

Design and purpose

The roof lathing is a simple structure consisting of small cross-section rails fixed perpendicular to the frame's truss legs. This specific flooring can be made of wood or metal, varying the distance between the elements depending on the slope and roof structure, as well as on the type of roofing material chosen. The crate in the design of the truss frame performs the following functions:

• The distribution of the load from the roofing pie. Each square meter of the roof together with the snow mass can weigh more than 300 kg, so it is important to evenly distribute this weight between the rafters so that the roof does not deform.
• Shaping down The flooring of boards, plywood or slats, laid across the rafters, serves as the base on which the roof covering is laid and fixed. Extra support for soft materials and high weight coatings is especially important.
• For fixing roofing. Correctly chosen step of the batten allows the roofing material to be fixed evenly with the help of fasteners, thanks to which it can withstand more wind load.

Important! Properly designed obreshetka allows you to reinforce those places of the truss frame, which are subject to increased loads, for example, valleys, areas where gutters or snow holders are attached.

Materials

Many inexperienced builders wonder how to make the crate with their own hands, and, most importantly, from what. The fact is that it must be strong, reliable, durable, but at the same time light, so that it does not overly weigh down the structure. Depending on the method of arrangement for the manufacture of crates used:

1. Edged and unedged board. Natural wood - the most popular material used for the manufacture of flooring, which is attached to the roofing, as it is lightweight and durable. With the help of boards, you can make a solid, lattice or sparse crate, so this is a universal version of the flooring suitable for almost any roofing. Wooden crate has only one drawback - weak resistance to moisture, so it must be painted or impregnated with an antiseptic.

   

2. Moisture-resistant plywood or OSB. Various wood processing products are used to make a continuous batten, which is necessary for flooring soft roofing (ondulin, shingles, roofing membranes, roofing material), heavy materials (ceramic tile, slate) or for blocking rats with a minimum slope.
3. Metallic profile. A square hollow profile, metal corners or pipes are used to make a roof crate with a greater bearing capacity with relatively light weight, which is used to overlap roofs with a large area. It costs more than wood, but it lasts much longer, since it has high anti-corrosion properties.

Professional roofers consider it expedient to create a batten from a metal profile, which is more expensive only if the length of the roofing slope exceeds 6 meters, and the waterproofing coating is heavy.

Ways of arrangement

There are three main parameters of the design of the flooring on which the roofing installation should be made: the pitch of the batten, as well as the cross section of its elements and the material used for its construction. However, there is one more characteristic, the choice of which depends on the composition of the roofing pie. Lathing device can be:

• Single Layer. The single-layer lathing consists of only one tier of the rails, which are fixed across the rafter legs with a predetermined step during the calculation. The difference between this option is that between the wooden frame and the roofing coating does not form a gap in which air circulates. Therefore, this design is used when installing roofs "cold" type.
• Dual Layer. The two-layer construction consists of two tiers of the rails: a contra-lattice fixed along the rafter legs and the sheath itself located across them. Such a device allows forming a ventilation gap between the wooden elements of the frame and the roof covering of the roof, protecting them from contact with condensate and atmospheric moisture. Therefore, this design option is used when installing a "warm" roof, which includes insulation.

Remember that between the crate and the rafter legs must be laid waterproofing film that protects the roof frame from contact with water. Waterproofing is cut into strips, and then fixed with a construction stapler with strips across the roof truss. If desired, the joints between the strips can be glued with adhesive tape.

Kinds

Before you make a crate for the roof with your own hands, you need to calculate the total weight of the roofing pie, taking into account the maximum possible snow load in the winter period. These calculations will help determine the required bearing capacity of the flooring, and on the basis of this factor, you can choose the cross section of its elements and the distance between them. Metal or wooden lathing can have the following appearance:

1. Solid. Solid flooring is installed if the roof covering used to overlap the roof is of a soft type. Since it is not able to hold the form on its own, it requires a solid base of moisture-resistant plywood or OSB, the distance between the sheets when laying should not exceed 1 cm.
2. Grid. A lattice is called lattice or standard, if the distance between its elements is 25-45 cm. It is made of cut or unedged board or timber and is suitable for mounting most sheet roofing materials, as it provides a good level of support.
3. Sparse. She considers sparse lathing if the distance between adjacent laths exceeds 50 cm. Usually it is made of a metal profile welded between, as it should have a large bearing capacity. With the help of a rarefied base, roofs with a large area are overlapped, and also when heavy roofing materials are being installed for the purpose of reducing the weight of the structure.

Note that the appearance of the flooring used for fixing the roof covering is influenced not only by the material from which it is made, but also by the sheathing step. The heavier the roof and the gentler slopes, the less should be the distance between adjacent rails.

Criterias of choice

The choice of lathing is based on a competent calculation, taking into account all the features of the design of the roof. These calculations help to find the optimal material for its manufacture, the required cross section and the distance between its elements. The following criteria influence the design choice:

• The angle of slope of the roof. The greater the slope, the less snow accumulates on the surface of the roof, which means less stress on the roof frame, due to which it is possible to increase the step between the elements of the batten.
• Type of roofing. If the material has a rigid shape and is not deformed during operation, then a sparse or lattice crate is used for its installation, since it requires minimal support. Soft coatings, on the contrary, are laid on a solid foundation.
• Climatic conditions. If construction is carried out in a region with snowy winters, then the crate should be strengthened with additional elements so that it is able to withstand the additional load during snowfall.

Remember that the installation of the batten is done after the installation of the roof pairs, when their upper edges are aligned to the building level and are in the same plane, otherwise the roof will turn out to be a curve.

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