Gable roof lathing for corrugated board. Roof lathing for corrugated board: materials, technology and installation nuances. Metal lathing: the perfect solution

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One of the most crucial moments when installing a profiled sheet is to create a frame on which the roof will creep. In order for the lathing to be able to withstand significant loads and correctly distribute the weight of the roof, it must be strong enough, like the entire rafter system (read also: ""). The lathing under the profiled sheet is made by installing beams or boards on a support with further installation of roofing material on them. The lathing for a metal profile allows you to speed up the process of installing sheets, since the fastening of the roof is greatly simplified. Also, the lathing allows you to organize the correct ventilation system in the under-roof space.

The lathing device for corrugated board can be carried out using different materials. For private houses, the most common lathing is made of wood; in the case of industrial buildings, it is much more efficient to use. This makes it possible to withstand large loads on the sheathing system compared to a private house.

The thickness of the boards or beams depends on which step of the sheathing for the corrugated board was chosen. It, in turn, depends on the type of metal profile.

Installation of the lathing

Let's consider how to make a crate for corrugated board. The main board of the crate, which will run along the eaves, is always taken thicker than the rest. In places where it is planned to install a ventilation outlet, chimney or fire hatch, additional boards are installed. installed on top of a layer of hydro and thermal insulation. It is also important to remove ventilation.

Having decided on the main purpose of the roof and calculating the possible loads, they proceed to the choice of roofing material and the calculation of the sheathing. The correct choice of corrugated board and the optimally selected pitch of the sheathing for the corrugated board are the key to a long service life of the roof.

Profiled sheet profile parameters

When choosing a material, it should be remembered that the higher the height of the profile, the higher the load that the profiled sheet will withstand.

At first glance, it may seem that the main element of any pitched roof is the rafters. But this statement can be safely argued. The main function of the rafter system is to transfer the load to the supporting building structures, that is, the walls and foundation of the building.

External loads acting on the roofing system are very high. These are hurricane winds, torrential rains, and heavy snowfalls. But all of them, first of all, affect the roof covering attached to the crate. Therefore, it is the roof lathing for corrugated board that, in fact, is the main element of the roof structure.

Lathing for corrugated board on a roof made of wooden beams

It is the destruction of the sheathing under the corrugated board due to errors in the calculation or poor installation quality that leads to sagging of the roof, violation of hydro and thermal insulation, and even to a collapse of the roof. A greater disaster, especially if it happens in cold inclement weather, is difficult even to imagine. Therefore, the device for the sheathing for corrugated board must be carried out with special care and accuracy.

What material to use for the sheathing for the corrugated board?

A crate for a profiled sheet is called a special frame, which is designed for attaching steam and waterproofing, insulation and roofing. The lathing is made of wooden or metal structures.

Metal sheathing for corrugated board is used more often for roof frames of industrial buildings and, much less often, for cold non-insulated roofs. This is due to the greater load-bearing capacity, strength and durability compared to wooden options.

The device of the roofing pie - vapor barrier, waterproofing, insulation, counter-lattice and, in fact, the roof lathing itself under the profiled sheet

The rafter system and lathing of individual residential buildings are usually made of wood. Wooden lathing for corrugated boarding is much cheaper than metal and, importantly, much easier to install.

For the construction of the lathing, a wooden beam with a size of 40x50 or 50x50 mm is usually used, or an edged board with a thickness of at least 20 mm. In the latter case, as a rule, a board of 30x100 mm is taken.

Its strength depends on the size of the lumber used for the manufacture of the lathing. These dimensions are determined when calculating the bearing capacity of the entire roofing system. So, for example, the dimensions of a wooden beam for a lathing significantly depend on which step of the rafters and the step of the lathing for the corrugated board is chosen. The larger it is, the thicker the timber or board should be.

Lathing for profiled sheet - types and design features depending on the slope

There are two main types of battens used in the construction of residential buildings - solid and thinned. The device of a continuous crate is determined by its very name - boards or beams in it are mounted close to each other. Usually, to save material, a solid crate is made of a board.

In a sparse crate, the bars are installed perpendicular to the rafters at regular intervals. These gaps are the so-called step of the sheathing for corrugated board. It depends on the height of the wave or trapezium of the corrugated board, which determine its own bearing capacity.

Lathing for wall sheeting C21: 1 - counter lathing, 2 - profiled sheet, 3 - lathing step

For example, the pitch of the lathing for C21 corrugated board should be at least 300 mm with a relatively small slope of 7-8 °. Moreover, the greater the angle of inclination, the larger the step and the lower the bearing capacity should be the corrugated board. In particular, the lathing for the C-21 corrugated board with an angle of inclination of the roof of more than 15 ° should be with a pitch of 650 mm, which is more than twice as large as in the previous case.

The table below contains data on the required distance between the boards for the most popular grades of corrugated board and for two slope options.

The calculation of the lathing for the corrugated board is made on the basis of the planned slope and the brand of the corrugated sheet. In addition, the coefficients of wind and snow loads for areas with special operating conditions are taken into account without fail. In particular, for areas with frequent and strong winds, it is recommended to significantly reduce the pitch of the crate, up to a twofold reduction.

It should be borne in mind that the lathing for the profiled sheet is only the top layer of the roofing pie, to which the profiled flooring is directly attached. In addition to it, there is also the so-called counter-lattice.

It is made of a bar with a thickness of 30-40 mm and serves to create a ventilation gap under the roofing sheets. The bars of the counter-lattice are attached on top of the vapor barrier laid on the rafters along the rafter legs, and the lathing itself is already attached to them.

Sheathing for corrugated board - installation features

The installation of the lathing under the corrugated board has its own characteristics, which are regulated by building codes. Before construction, they must be studied without fail, because after reading these standards, you will know how to make a crate for corrugated board reliable and durable.

So, according to the requirements of building codes, all wooden roof structures must be antiseptic. This is especially important for the lathing. If the rafter system is located in a ventilated under-roof space and, moreover, is additionally protected by waterproofing, then the lathing for the roofing sheeting is separated from the ambient air only by the profiled sheet itself.

In addition, humid outside air constantly circulates in the under-roof ventilation gap. Therefore, special attention should be paid to antiseptic processing of wooden structures of the crate.

This is all the more important due to the fact that the lathing of the roof under the corrugated board is not accessible for inspection with impossible periodic revisions of the rafter system. From the inside, it is closed with a layer of vapor barrier and insulation, and from the outside - with a profiled sheet. Therefore, it will be possible to see only the results of its destruction from exposure to moisture. At the same time, the elimination of such consequences will require an expensive overhaul of the roof.

It is also important to take into account the peculiarities of installing the lathing in the area of ​​the roof ridge, on cornices, pediments and at the junctions to the passages through the roof of the smoke and ventilation ducts.

Steel bent profiles - corrugated board - wall and roofing material made of thin metal. Its qualities:
- Durability
- Versatility
- Durability
- Lightness
- Refractoriness

On the front side - a protective polymer coating, on the other - a protective varnish. Profiled sheeting is used for roofing, walls, fences, sandwich panels.

Step and size of the lathing for corrugated board

Despite the strength of the corrugated board, it shows its best qualities, securely fixed on a correctly made frame or crate. The higher the profile of the sheet, the more loads it will withstand in the future.

The lathing frame is the basis of any roof; its step is very important for the durability of a corrugated roof. If you correctly calculate the distance between the bars, the load on the sheet will be evenly distributed, it will not deform during snowfalls and other mechanical influences.

The step of the lathing depends on the type of corrugated board.

For a thin profiled sheet of grade C, a continuous crate is arranged, where the minimum gap is 10 cm. A simple solution is to use sheet material - wood-based panels, plywood. For strong sheets of grade CH and H, you can take a step between the beams of 50-70 cm, you get a sparse crate.

The most durable, but also the most expensive roof will be obtained using sheets with a thickness of 0.6-0.7 mm, whose profile is 3.5 cm. The spacing of the sparse sheathing can reach 1.5 meters. The load that such a coating can withstand is up to 600 kg per square meter.

In general, working with a hand tool for cutting profiled sheets is very laborious, takes a lot of time and effort. This allows us to conclude that cutting the corrugated board using a hand tool is ineffective and unprofitable.

Choosing a base for a professional sheet of different brands:

• For corrugated sheet of grade C20, the crate must be solid
• C35 - step no more than 30 centimeters
• С10 - solid crate
• C21 - standard, with a step of 30 cm
• C44 - a thin base is suitable

The step of the lathing depending on the type of corrugated board

Installation of lathing for corrugated board

If the building will be heated, then a waterproofing membrane is laid on top of the rafters. The film is laid out from bottom to top in horizontal rows. The overlap will allow moisture to flow freely over it. On the rafters, the membrane is fixed with a stapler.

The roof lathing for the corrugated board is mounted in parallel with the membrane fixation.

To increase the area of ​​the ventilated space, the membrane must not be stretched, it should sag slightly.

Sheathing boards are treated with antiseptics and fire retardants. This operation is performed prior to installation, so that the wood is evenly impregnated.

For the entire length of the rafters, a support bar with a section of 5x4 cm is fixed with self-tapping screws.You can use a whole bar, fixing it every 40 cm, or take shorter workpieces. The transverse crate is made from a 2.5x15 cm edged board.Using a stretched fishing line, they control how evenly the boards are located.

If the boards of the sheathing have to be spliced ​​along the length, their joint should fall on the rafters; in adjacent rows, the joints should not be at the same level.

The first and last rafter boards are fixed directly to the edge of the rafters. For those boards that will be between them, a step is chosen that is convenient for fixing the corrugated board of the selected brand. To be sure, you can use a template of the desired width.

Places where there will be a hatch for ventilation, a chimney, are strengthened with additional boards, to which sealing aprons are attached.

Having completed the work on one side of the roof, they move to the second slope. Having fixed the crate and the membrane there, the last is fixed to the ridge board, covering the same element of the other slope. To correctly perform this operation, the board of the other slope is planed with a plane.

The wind bar for corrugated sheathing should be thicker than the rest of the sheathing elements. The peculiarity of its fastening is that it should be located at the end of the sheathing, protruding to the height of the roofing sheet.

Sheathing scheme for corrugated board

Fastening the corrugated board to the crate

It is convenient when the length of the roofing sheet matches the length of the roof slope.

When ordering corrugated board, it is necessary to take into account the length of one rafter, adding 5-7 centimeters.

The delivered sheets are not pulled off, but removed from the bundle. It is convenient to lift them to the roof using guide rails. Do-it-yourself installation of corrugated board begins with even laying of the first sheet, which determines the geometry of the entire roof. Beacons - temporary slats protruding upward behind the cornice - will help to align it along the pediment.

It is best to fix the sheet on the crate with self-tapping screws with rubber washers, the places for them can be marked in advance. The self-tapping screw should gently press the metal cover, but not deform it. Installed in place, a metal sheet is connected to the adjacent one with rivets in the color of the decorative coating of the sheet.

Attention: there should be 6-8 pieces of self-tapping screws on one square meter of the roof.

If the sheet needs to be cut, the cut is located at the ridge. In the direction of the cornice, a cut made at the factory is turned.

The wind bar and the ridge are installed immediately, so that later you do not have to move along the profiled sheet, risking slipping and crushing the metal. Long drills with a rubber seal are used to fix the ridge elements. Having passed through the external wave of the corrugated board, the drill is fixed in a wooden beam.

Despite its strength, the corrugated board, made of thin rolled steel, needs a perfectly flat base that ensures an even distribution of the load. The larger the pitch of the lathing, the thicker the timber or board should be.

Video about the crate for corrugated board

Video instructions for installing the lathing with an illustrative example will make it easier for you to build it. The last video talks about how to properly attach the corrugated board to the crate.

The use of corrugated board allows you to equip a high-quality, functional roof. To ensure the reliability and durability of the coating, it is important that the lathing for the corrugated board is correctly calculated and correctly mounted.

Features of the profiled sheet

Decking is a fairly light and durable roofing material made of steel sheet. The rigidity of the profiled sheet depends on the thickness of the metal, as well as on the depth and configuration of the profile, the width of the corrugation. The step of the lathing on which this material is attached directly depends on the characteristics of a particular brand of corrugated board, the angle of inclination of the roof, the expected operational loads.

The higher the profile height, the higher the ultimate load that the profiled sheet can withstand.

The device of the sheathing for the corrugated board requires the use of wooden beams or boards, laid close or in a row perpendicular to the rafters. This structure provides the necessary strength of the roof, its resistance and uniform distribution of external loads.

It is installed when erecting truss systems made of wood or metal, as well as on roofs with a slight slope, made of reinforced concrete slabs. Installation of wooden lathing under the corrugated board is carried out using staples, nails, self-tapping screws, dowel-nails, depending on the material of the rafter frame or the base of the roof.

Principles of calculating the sheathing for corrugated board

Like most roof coverings, the profiled sheet is attached to the battens. The step of the lathing for the corrugated board is stipulated in the building codes. SNiP specifies the requirements for this parameter, based on the angle of inclination of the roof slope:

• with a minimum roof slope, for the installation of corrugated board, a solid lathing is required, or a lathing with a step not exceeding 400 mm (the choice depends on the thickness of the metal and the grade of the material used);
• with an average slope, the wooden base can be mounted with a step of 300 - 650 mm;
• if the roof has a large slope angle, the step can be up to 1000 mm;
• individual grades of corrugated board with high rigidity can be mounted with a lathing step of up to 300 or 400 mm, if the slope of the slope is more than 8 degrees.

More details about the dependence of the lathing pitch on the profile brand can be found in the table:

Table. Dependence of the step of the crate on the brand of corrugated board

When designing a roofing system, you should decide in advance on the material of the topcoat. Manufacturers of corrugated board in the accompanying documentation indicate the requirements for laying a specific material. It is recommended to calculate the sheathing for corrugated board, in accordance with the parameters specified by the manufacturer (they do not go beyond the requirements of SNiP).

In private construction, corrugated board with a profile of 35 mm in height from a steel sheet with a thickness of 0.6-0.7 mm is often chosen. Such material can be mounted on the purlin in steps of up to 1.5 meters, while the roof is designed for a load of up to 600 kg per square meter. You can safely move along such a roof when cleaning or repairing, but it should be noted that this structure of increased strength is somewhat more expensive than a roof made of corrugated board of lower rigidity.

If it is supposed to use corrugated board with a profile height of 21 mm or less, the step of the lathing for the corrugated board should be minimal, or a continuous lathing is mounted. This roofing material is not designed for high loads, it requires a solid base to avoid deformation of the sheets.

Profiled sheet with a profile height of 44 mm is practically not used in private construction, since this material is intended for the construction of the roof of industrial structures.

Preparation of material for lathing

To calculate the amount of lumber required, you need to know the length and width of the ramp, as well as calculate the step. In addition, it should be taken into account that two boards should be mounted at the ridge and the cornice in order to ensure the necessary strength of the roofing flooring. Reinforcements also require places of abutment to chimneys, skylights, ventilation ducts, etc. Another 10% should be added to the result of the calculations, since during the installation process the lumber will have to be cut to the required size and some will go to waste.

The cross-section of the bar must be at least 50 × 50 mm. Also, the lathing can be made of edged or unedged boards with a thickness of 50 mm. It is required to use well-dried lumber. It is recommended to use beams and boards made of spruce, pine, beech, alder. The material may not be planed, but you should pay attention to the straightness of its surfaces.

Boards and beams should not be warped; if necessary, the surface of the elements should be corrected.

The lathing for corrugated board is operated in conditions of high humidity, therefore there is a high risk of damage to wooden elements by fungus and microorganisms. To prevent wood rotting, lumber needs to be treated with antiseptics. Fire protection of roof elements is also required. Today, special compositions for fire-retardant protection are produced, which allow both types of treatment to be carried out at one time.

It is allowed to process an already finished crate, but the roof structure will be much more efficiently protected if it is assembled from elements that have been qualitatively impregnated with a fire retardant compound in advance.

Installation of lathing

How to make a crate for corrugated board? First of all, you should pay attention to the structure of the roofing pie of the pitched roof, if corrugated board is used as the topcoat. On top of the rafters, it is required to lay waterproofing from roofing material or a special waterproof membrane. requires high-quality ventilation, therefore, along the rafters, on top of the waterproofing, it is necessary to fill the bars with a cross section of 50 × 50 mm - the counter lattice makes it possible to create the required ventilation gap.

The battens are attached to the counter battens. For this, boards or bars are stuffed parallel to the cornice strictly horizontally. To simplify installation, it is recommended to tighten the rope by fixing it along the edges of the ramp and making sure it is horizontal, it is better to use a wooden template. The lathing is attached to the wooden bars of the counter-lattice with staples or nails, if metal elements are used, self-tapping screws should be used. It is attached to the concrete base of the roof using dowels.

In the lower part of the ramp, parallel to the cornice, the main board of the sheathing is attached, its thickness should be greater than that of the other elements. The thickness of the board is selected based on the height of the profile of the profiled sheet, as well as the length of the fasteners used, with which the outer side of the roofing sheet is fixed. It is necessary to install wind boards at the ends of the roof slope. Their surface should be higher than the rest of the lathing elements, to the height of the corrugated board profile.

Installation of the lathing under the corrugated board is then carried out in the direction from the bottom up. Each bar is attached to each rafter with one nail. To fasten the board to each rafter, two nails should be used along the top and bottom edges to avoid turning the board over and damaging the roofing under high loads. The elements of the lathing should be docked along the length on the rafter, securing each of the ends with nails or staples. On one rafter leg, the sheathing of adjacent tiers should not be joined.

How to make a crate for corrugated board, observing the installation technology, you can learn from a specially prepared video.

Today, many people prefer corrugated board as a lightweight, even and easy-to-install roofing material. It is not difficult to work with it, and any person can do it, just choose a high-quality mount and prepare the right base.

And in this article we will tell you what the crate should be for corrugated board of different types and shapes, with what step it should be mounted and what this step depends on. And our video tutorials and detailed illustrations will help you understand all the intricacies of such a design!

Imagine what happens if the sheathing for the corrugated board is not frequent enough: the sheets will easily bend not only under your weight, but also under a cap of snow, and in the spring the roof will look depressing.

Calculation and design of the lathing

Let's first understand the concepts. So, the lathing is a solid flooring or lattice structure that is mounted on top of the rafters and serves as the basis for fastening the roofing material. The lathing itself strengthens the spatial structure of the roof due to its rigidity, and it is made either from wood or from metal.

The extent to which the sheathing for the corrugated board will be sparse or solid depends on the roof itself. Solid flooring is called a flooring with a gap of up to 1 cm (i.e. not 100% monolithic), and such a sheathing is suitable for roll materials, flat slate and soft tiles. Solid flooring is also done partially at the intersection or junction of the slopes, along the eaves.

The most difficult is the sheathing of the hip roof:

Taking into account climatic conditions: snow and wind

The slope angle of the roof plays an important role. When the slope is steep, more than 45 °, snow and water are easily removed from it, but the steeper the slope, the more expensive it is to build the roof itself, and the more lumber will go to the crate.

Let's compare: for a roof with a slope of 45 °, one and a half times more building materials are used than for a flat one, and with a slope of 60 °, it is already twice as much. But the climate also plays a role.

So, for areas where there are strong winds, it is necessary to make the most gentle roofs, because corrugated board is the most sailing material of all existing roofs. In hurricanes, such coverings are torn down by the roots, so it is better not to give faith a chance. But in snowy areas, where the winds are not strong, I make steep slopes.

This reduces the snow load, because snow falls off such slopes by itself. And this is especially true for corrugated board, which is produced quite thin and can really bend under the snow (especially if the sheathing step was installed "by eye".

Consider also that the more dense the crate is made, the more it weighs. And all this is important to take into account when calculating the load on the foundation. Specifically, for the construction of a roof from corrugated board, coniferous bars are most often used, and their weight per cubic meter is from 500 to 550 kg. For comparison: OSB and plywood with the same volume will weigh 600-650 kg / m 3.

First of all, let's decide whether it is worth counting a crate for corrugated board at all. After all, quite often there is an opinion that it is easy to pick up a step, literally "by eye" or like a neighbor's, because the material is unpretentious. But in this case, you run the risk of facing the following consequences:

• Exceeding the cost of the roof, if the step of the sheathing was advised by the reinsurer.
• The deflection of the corrugated board under the first snow, if everything was done at random.
• Inconvenient fastening of sheets, when the edges of the corrugated board fall between the laths.
• Inability to carry out repair work due to the fact that it is dangerous to walk on the roof.

Therefore, so that neither "under" or "over" will work, and you are calm about your home, still make the necessary calculations.

You have several paths:

1. Use a special online calculator directly on the professional flooring manufacturer's website, which will calculate everything quite accurately.
2. Study a finished project that has been developed for your area and the same roofing. Surely there are such houses in the district, just do not take as an example the objects of self-builders, whose only consultants are members of the forum.
3. Consult with foremen who are already building near you. The fact is that the load on the lathing is calculated for 1 m 2, therefore, in principle, it does not matter what your roof length is, the main thing is that the angle coincides. This opinion is worth trusting, because in professional design they adhere to certain building codes and regulations.

If you do not regret calculating the time, you will benefit in the quality of the roof and significant savings in material for it. Snow and wind can create a load of more than 300-500 kg for each square meter of the roof!

Let's just say: a rafter system is a complex engineering structure that is not created “on the knee”. Indeed, there are no insignificant trifles in the roof, and even insignificant savings on the same crate in the future will necessarily result in more significant repair costs. And it is very difficult to remake the roof.

If, of course, you will lay the profiled sheet on a small roof above the garage, gazebo or shed, then you just need to visually understand how strong the crate should be and compare your data with the tables. So many do, and often their approximate calculations are correct:

If we are talking about the roof of a residential building, it is necessary to approach the issue of calculating the sheathing for corrugated board very responsibly. So, for different tasks and types of corrugated board, the following types of sheathing are used:

• Solid sheathing made of OSB or plywood. Required for minimum roof slopes.
• Solid lathing made of bars or boards, which I lay parallel to each other with a small gap. This option is suitable for non-corrugated corrugated board.
• Sparse lathing with solid counter-lattice. So, if the lathing was laid with a large step, then counter-rails are laid along the diagonal of the roof for additional rigidity.
• Sparse lathing for corrugated corrugated board, with a step several times smaller than the sheet itself.

But a sparse lathing for a large-sized roof is not suitable, because it is calculated so that the sheet lays down only two bars. Unfortunately, corrugated board is not such a durable material.

For the device of a continuous lathing, boards with a thickness of 30-40 mm are taken. It is not recommended to take boards wider than 140 mm, because this can warp.

By the way, almost no one makes a solid crate from boards for corrugated boarding, and it is replaced with a more practical sheathing of slopes with OSB plates or moisture-resistant plywood.

Sparse sheathing: for steep roofs

Traditionally, a sparse crate is equipped with a modern corrugated board. It is allowed to make it under rigid roofing material that withstands wind and snow loads well enough without collapsing or sagging.

For a sparse lathing, sawn wooden blocks and wooden poles are suitable. The main requirement for them is to have a minimum internal humidity, within 18-20%, not to have deformations, bends and knots. Such a crate must be treated with an antiseptic and, if desired, a fire retardant. Also, a sparse lathing for corrugated board is made of U-shaped galvanized laths.

The standard pitch of the lathing for corrugated boarding for the central strip of Russia is 35-40 cm, when using bars with a section of 50x50 mm or boards of 50x120 (140) mm.

Also, the crate is equipped with a single-layer or two-layer, but specifically for corrugated board one layer is enough.

Sheathing step and corrugation height

The step of the lathing installation under the corrugated board also depends on the type of profiles of the sheets themselves. Each profile has its own bearing capacity, which is determined by the height of the corrugation and the thickness of the rolled steel. For example, for grades with a bearing capacity, a continuous crate is laid, and with a high one - a sparse one.

For pitched roofs, the corrugated board is taken with a corrugation of at least 20 mm. These are NS-35, MP-20, S-44. And profiles Н-60 and Н-75 are used for self-supporting and flat roofs of industrial facilities:

In any case, the minimum section should be 30x100 mm, if the distance between the rafters is up to 1000 mm:

Lathing for certain types of corrugated board

Let's also outline some of the features of the lathing device for the most popular types of corrugated board, which are used in the construction of a private house.

So, if you use a C-8 profiled sheet on a roof from 15 °, then either take it with a thickness of 0.55 mm (be sure to check with a micrometer), or lay a continuous crate.

When working with profiled sheet MP-20, P-18, take sheets from 0.7 to 0.55 mm, and make a continuous flooring if the slope is up to 15 ° and a sparse crate, if more, keeping the distance between the boards up to 5 cm. The H-35 corrugated board of the same thickness, already up to 15 °, is allowed to be laid on the crate with a step of 50 cm and from 15 ° with a step of 1 meter, here the strength is just enough. At the same time, the same conditions for C-44 corrugated board, if the thickness of its sheet is within 0.55-0.7 mm.

For H-60 ​​profiled sheet, the roof slope is not less than 8 °, and the sheet thickness should be 0.7-0.9 mm. The step of laying the lathing is already done no more than 3 meters.

This table will help you figure things out:

By the way, if you are still worried that a heavy cap of snow will fall from the main roof of the house, then it will not be a pity to arrange a continuous flooring for an extension:

Choice of material: wood vs metal

As for the material for making the lathing, there are two options: metal and wood. So, metal strong rafter systems today are more often chosen for industrial high-rise buildings, where high strength, fire safety and relatively low weight are important.

Wooden lathing: a building classic

If you opted for a wooden crate, then when buying, arm yourself with a ruler and check all the declared parameters. As a material, take bars with a section of 50x50 mm or 23x50, or boards 32x100 and 50x100 mm. The main thing is that they are treated with an antiseptic.

Also count the number of extra bars to bypass chimneys, fire hatches, and other similar locations. In those places, the consumption of wood will be twice as much. In addition, not one, but two boards are laid at the edges of the roof for added strength. As an alternative to the bars, a board is also used, with a thickness of 50 mm:

Alder, beech, spruce and pine are suitable as wood for the sheathing under the corrugated board. You need to wake them up with an antiseptic and fire retardant, or purchase already prepared for construction. The main thing is to protect the crate from rotting and fungus, because moisture in the under-roof space is not so rare.

Let's take a look at how thick the wooden lathing should be. So, the most popular is a board with a section of 22x100 and 25x100 mm. It is affordable, but only suitable for simple lightweight roofs due to lack of strength. A 32x100 mm board is considered more suitable. This can be used to install a sparse sheathing on the rafters with a step of 90 cm.

Grooved boards, 25 and 32 mm, with a tongue-and-groove connection are also suitable for continuous sheathing.

Calibrated boards are taken to create a sparse sheathing for corrugated board. They are durable, well-crafted, accurate geometries, but expensive.

Lathing from a bar of 50x50 mm is made already at a step of rafters from 90 cm, and without such material one cannot do in working with complex structures, which have many additional elements. The bars themselves are strong and thick, and therefore well protect the metal roof from deflection. That is why a timber as a lathing is most often found with a high corrugation corrugated board, which is initially laid in order to withstand a significant load. Planks won't help here, of course.

But for arranging a wooden lathing for corrugated boarding, it is not recommended to use half-edged and uncut lumber. Here are some good tips from a professional roofer to show you how to work with wood sheathing:

Metal lathing: the perfect solution

Today, the use of metal lathing for private construction is becoming especially relevant, especially in urban conditions. Moreover, it makes sense to initially build an all-metal roof: with steel rafters, and with steel crate, and with steel corrugated board. As a result, such a roof turns out:

• relatively light (lighter than a wooden truss system), absolutely not susceptible to insects, rotting and fire;
• perfectly flat, without a knot or hitch, which cannot be said about wood;
• does not bend or deform over time;
• fully compatible with profiled steel sheets.

Mount the metal crate on the rafters using bolts or welding. If the same raw materials were taken for the manufacture of rafters and lathing, then the fastening is reliable. Those. here you will be spared unwanted chemical reactions due to the junction of dissimilar materials like metal and wood.

There is no problematic "wood-metal" contact, convenient fastening, high fire safety and reliability of the roof itself. Moreover, the roof with metal rafters and crate is also insulated! Therefore, such a steel frame does not in any way interfere with the arrangement of a cozy and warm attic.

And the thickness of the metal lathing for the corrugated board is no longer difficult to choose. It depends on the height of the steel profile used.

Here are the basic requirements for metal sheathing for corrugated board:

1. The fastening of the sheets must be reliable and withstand local climatic conditions.
2. The thickness of the sheets must be selected according to the step of the metal crate.
3. The step of the lathing should be calculated according to the same scheme as the wooden one.

For the manufacture of metal lathing, both galvanized steel and aluminum-zinc coated steel are suitable.

The most important thing is to mount the frame so that in the end all its elements are in the same plane. If the batten is wooden, line it with wooden wedges. If it is metal, most likely, it will initially be more accurately mounted than wooden.

And all thanks to the exact geometric parameters of all parts. Plus, the metal frame is more resilient. And for arranging a roof for corrugated boarding, some metal rafters are enough, but more often it is necessary to make an additional crate to increase the rigidity.

Master class: how to make and install a crate

Now we will show you in practice how to make a crate for corrugated board yourself. There is a definite difference in technology if you are building a cold roof for an attic or a warm one for an attic. So, for a cold roof, it will be enough to lay a dense wind-waterproofing, and fix it on top with a crate. And for arranging the roof of an ordinary gazebo, a simpler option is also suitable:

For a workshop or a small bath, the crate already needs to be done according to all the rules:

If we are talking about the insulation of slopes, such waterproofing must be "breathable". For this purpose, it is advised to use modern superdiffuse under-roofing membranes with high vapor permeability.

Even if you are building a cold attic right now, do just that. Over time, when you understand how valuable and useful living space is, you will want to make the attic residential, and in this case, you just have to insulate the sloped walls from the inside - and you're done. But if non-breathable waterproofing was laid on the slopes under the crate, there will be a lot of work.

In addition, a superdiffusion roofing membrane does not require a special ventilation gap between the insulation and the film, as is necessary with films of low vapor permeability. Just be careful: membranes with high vapor permeability have front and back sides, and it is advisable not to confuse them.

The outer side is often made in color, with branded markings. In addition, usually the membrane is rolled into rolls so that it is convenient to roll it out on the rafters. Therefore, first of all, nail two boards of 50x50 (50x100) and 32x50 (32x100) mm along the eaves, one on top of the other, and lay waterproofing on top of these boards.

The first layer of membrane should be rolled out along the roof overhang so that the edge descends just into the gutter. The overlap of the strips is 10-15 cm, be guided by the line marked with a dotted line on the roll:

Next, nail down the falling bars of the counter-lattice 50x50 mm over the waterproofing. This must be done! After all, a roof made of corrugated board must be ventilated (remember about condensation and corrosion), it is these bars that will create a ventilation gap.

Secure the counter grill with wood screws or galvanized nails. Do not use non-galvanized hardware, because due to corrosion, wooden blocks will start to rot.

And the eaves overhang is most often covered with a ventilation mesh. At this stage, install the drainage system (we will not dwell on this in detail).

Now lay the sheathing bars under the ridge, and also cover with waterproofing. We turn to the construction of the lathing. For this purpose, a metal bar is applied, nails are driven under it and the marking lace is stretched. This is the most proven method for level mounting.

Planks or lathing bars must be placed strictly parallel to the cornice, and fastened to the base with nails, staples or even dowels in some cases. Work from bottom to top, attaching each block to each rafter with one nail or staple.

If your crate is made of boards, then you need to fasten it in two nails along the lower and upper edges, so that over time, under high loads, the boards do not turn out, and the roofing does not get damaged.

But the principle is one: join the crate elements only on the rafters, and do not leave their ends loose. At the same time, it is also impossible to dock the crate of adjacent tiers only on one rafter leg.

At the end, lay two rows of bars on the ridge roof under the future ridge element, and on the ends of the ramp - wind boards. At the same time, they should be at the height of the profile of the sheets, and exactly higher than the rest of the elements of the wooden lathing.

In addition to the "rope" method, such self-made tools are also practiced that greatly simplify and speed up the installation of the lathing:

Why so many worries, you ask? When the crate is ready, it should be a perfectly flat surface. Otherwise, there will be problems with the fastening of the corrugated board and the overall quality of installation.

Pay attention also to this point: if the rafters are not deep enough so that then between them you can lay insulation on its thickness, then you will need to attach an additional frame to the rafters.

In real life, it all looks like this:

As you can see, with the proper approach and adherence to the accuracy of the geometry of the sheathing, a neat and durable roof is obtained from the corrugated board!