How to make sheathing for corrugated sheets: a complete guide

Installing a roof or erecting a fence from corrugated sheets is a process where the quality of the foundation directly affects the durability of the entire structure. Sheathing for corrugated sheets performs the function of a load-bearing frame that takes on wind and snow loads, transferring them to the rafter system or foundation pillars. Errors at the stage of assembling the frame can lead to metal deflection, leaks and even roof collapse, so the choice of the design and pitch of the beams is approached with special care.

There are several types of frame, the choice of which depends on the purpose of the structure and the angle of inclination of the slope. For single-pitch roofs of garages, gable cottages or outbuildings, different approaches are used. Edged board, timber or metal profile pipe are the main materials used in modern construction. A correctly calculated pitch of elements allows you to save on materials without loss of strength, and also ensures a tight fit of corrugated sheets.

In this article we will analyze in detail the installation technology, SNiP standards for lathing pitches and the secrets of professional roofers. You will learn how to prepare lumber, why it is important waterproofing before starting work and what tools will be needed for a quality result. Understanding the physics of load distribution will help you avoid typical mistakes that beginners often make when building on their own.

Selection of materials and wood preparation

The foundation of a reliable roof or fence is high-quality material. Most often, edged softwood boards are used for wooden sheathing, as it has sufficient strength and resistance to rotting when properly processed. The moisture content of lumber should not exceed 20-22%, otherwise, after drying, the structure may collapse, which will lead to deformation of the roofing. Beam 50x50 mm or a board with a thickness of 25-32 mm and a width of 100-150 mm are considered the best options for most private buildings.

Before installation, all wooden elements must be processed antiseptic compounds and fire retardants. This extends the life of the structure by protecting it from mold, insects and fire. It is better to carry out impregnation in two layers, allowing each to dry according to the manufacturer's instructions. Some craftsmen prefer to use ready-made calibrated material, but its cost is much higher than that of a regular board.

An alternative to wood can be metal profile, especially if a fence or roofing of industrial facilities is being built. Metal lathing does not require antiseptic treatment, does not change geometry when temperature changes occur, and lasts for decades. However, it is more expensive and requires the use of special fasteners - self-tapping screws with EPDM washers or welding, which complicates the installation process at home.

• 🔨 Edged board - a classic option that requires pre-processing and calibration.
• 🏗️ Profile pipe - a durable solution for fences and flat roofs, resistant to corrosion when galvanized.
• 💧 Antiseptic - an essential component for protecting wood, extending the life of the frame up to 50 years.

Calculation of the sheathing pitch depending on the slope angle

The key parameter in the design is the sheathing pitch, that is, the distance between the centers of the beams. This indicator directly depends on the angle of inclination of the roof and the load-bearing capacity of the selected corrugated sheeting. The smaller the angle of the slope, the more snow will accumulate on the surface, therefore, the more often the frame elements should be located. For low-slope roofs with an angle of less than 15 degrees, it is often recommended continuous lathing, eliminating metal deflections under the weight of precipitation.

When the angle of inclination increases above 30-45 degrees, the snow load decreases and the pitch can be increased. In such cases, the distance between the boards can be from 300 to 600 mm or more, which allows significant savings on lumber. However, the wind load in a particular construction region should always be taken into account, as it also affects the structural rigidity requirements.

It is important to consider the brand of the profiled sheet. For roofing, a material with a wave height of at least 35 mm is usually used (for example, NS-35 or S-44), which has high rigidity. Wall profiled sheet (C-8, C-10) has a low wave height and requires more frequent steps or a solid base, otherwise it can be deformed even under the weight of a person during installation.

⚠️ Warning: Never rely solely on visual assessment. The calculation of the sheathing pitch should be made taking into account the maximum snow load for your region, specified in the building codes.

Installation technology: from cornice to ridge

Installation begins with installation cornice boards, which is attached to the ends of the rafter legs. It should be thicker than the main elements of the sheathing by the height of the corrugated sheet wave, so that the first sheet lies flat and does not sag. After this, the first lath is installed; the distance from the edge of the eaves is usually 300-400 mm, but the exact value depends on the length of the overhang.

Next, the pitch of the remaining bars is marked. For accuracy, you can make a template (conductor) from a strip of the required length, which will significantly speed up the process and eliminate errors. The boards are attached to the rafters with nails or self-tapping screws. The length of the fastener should be three times the thickness of the sheathing board to ensure reliable fixation. When joining boards along the length, the seam should fall on the rafter leg, and it is recommended to place the joints of adjacent rows in a checkerboard pattern.

In the area of the ridge and valleys (inner corners of the roof), sheathing is always done solid or with a reduced step. This is necessary to securely fasten additional elements and prevent leaks in the most vulnerable places. Reinforcement is also required around the chimney pipes and skylights, where additional bars are installed to secure the aprons.

Roof angle	Type of corrugated sheet	Recommended Step	Installation features
Less than 15°	NS-35, S-44	Solid or up to 150 mm	Requires waterproofing and reinforced fasteners
15° - 30°	NS-35, N-60	300 - 450 mm	Standard step, level check
More than 30°	Any roofing	500 - 600 mm	Saving material, a rare step

Features of lathing for a fence made of corrugated sheets

When erecting a fence, the role of sheathing is performed horizontal joists (veins) that are welded or screwed to vertical posts. Unlike the roof, there is no rafter system, and the entire wind load falls on the pillars and crossbars. For fences up to 2 meters high, two rows of joists are usually sufficient, located at a distance of 30 cm from the top and bottom of the fence. If the fence is high or the windage is large, add a third lag in the middle.

The material for the logs is most often a profile pipe with a cross section of 40x20 mm or 30x20 mm. Fastening to brick or concrete pillars is carried out through U-shaped brackets or clamps, and the logs are simply welded to the metal posts. It is important to maintain horizontal lines, otherwise the fence will look skewed, and the corrugated sheets may not meet at the joints.

Do you need a mortgage for a gate?

Yes, gates and gates require a reinforced frame. The pillars must be buried below the freezing depth, and the crossbars must be made of a larger cross-section pipe, for example 40x40 mm, to withstand the weight of the sashes and wind loads.

The corrugated sheet itself is attached to the joists using roofing screws in the lower part of the wave. The fastening pitch is usually one wave, and on the outer sheets and in windy regions - through the wave. This provides rigidity to the canvas and prevents it from flapping in the wind.

• 📏 Two logs - standard for fences up to 2 meters high in quiet regions.
• 🌪️ Three logs - necessary for high fences or places with strong winds.
• ⚙️ Profile 40x20 mm — the optimal cross-section for the crossbars, providing a balance between price and strength.

Waterproofing and ventilation of the under-roof space

Correctly made lathing is also a guarantee of effective ventilation. There should be a gap of at least 30-50 mm between the waterproofing film and the underside of the boards. This one ventilation gap allows air to circulate, removing moisture that condenses on the inside of the metal or penetrates through minor coating defects. Without ventilation, the wood will quickly rot and the insulation will lose its properties.

To create a gap on the rafters, a counter-lattice is often placed on top of the waterproofing - bars 30-50 mm thick, running along the slope. The main sheathing is already attached perpendicularly to them. This scheme is the most reliable for residential buildings with an insulated attic. For cold non-residential attics, the use of counter battens is also desirable, but in some cases it is permissible to attach thin lathing directly to the rafters with the waterproofing sagging between them by 2 cm.

⚠️ Attention: The waterproofing film cannot be stretched like a drum. Between the rafters it should sag slightly (10-20 mm) so that the material does not tear during thermal expansion or shrinkage of the house.

In places where pipes and communications pass, the waterproofing carpet must be carefully taped with special tapes and placed on vertical surfaces. The sheathing in these areas is done with a gap to leave space for installing walk-through elements and aprons.

Common mistakes and how to avoid them

One of the most common mistakes is to use uncalibrated board different thickness. This leads to the fact that the plane of the slope turns out to be wavy, the corrugated sheet lies unevenly, and cracks form at the joints. Before installation, it is advisable to sort out all the material and set aside bent or defective specimens for use in less critical places.

Another problem is saving on fasteners. Nails or screws must go deep enough into the body of the rafters or joists. If you use too short hardware, the structure may be torn off by a strong gust of wind. Also, you cannot ignore the protection of the ends of the boards: this is where rotting begins, so all cuts must be generously coated with an antiseptic.

Some developers forget that wood is a living material that reacts to changes in humidity. If you mount a damp board tightly end to end, when it dries, it may decrease in size and the sheathing pitch will increase, which is critical for corrugated sheeting with a narrow profile. Therefore, when using fresh lumber, it is recommended to leave small gaps between the elements.

Can I use leftover boards of different widths?

You can use boards of different widths, but only if they are the same thickness. The width only affects the pitch, which is easy to calculate, but different thicknesses will create level differences, which is unacceptable for a profiled sheet.

Do I need to paint the sheathing?

Painting is not necessary if a high-quality antiseptic is used. However, painting or treating with a fire-retardant compound that changes the color of the wood allows you to visually control the quality of the impregnation and serves as additional protection from UV radiation.

What is the sheathing pitch for profiled sheet C-8?

Profiled sheet C-8 has a low load-bearing capacity, so it is recommended that it be covered with continuous lathing or a pitch of no more than 100 mm, regardless of the angle of the slope, in order to avoid deformation of the wave flanges.