Choosing a roofing material for a garage is a task that requires a balanced approach, because the durability of the entire building depends on it. A garage is often a free-standing building or an extension that is subject to the aggressive effects of precipitation, wind and temperature changes. That's why corrugated sheet remains one of the most popular solutions due to its durability, ease of installation and affordable cost.
However, the variety of profiles, metal thicknesses and types of polymer coatings can confuse even an experienced builder. The wrong choice of sheet brand can lead to leaks, deformation of the roof under the weight of snow, or rapid corrosion. In this article, we will look at what technical characteristics are decisive for a garage roof and help you avoid common mistakes when purchasing material.
Before you go to the store, you need to clearly understand the difference between a wall and a load-bearing profile. Many owners try to save money by buying a thin wall sheet, without taking into account the snow loads of the region. This is a risky economy that can backfire in the first winter.
Key criteria for choosing corrugated roofing
The first thing you need to pay attention to is the marking of the sheet. Not all types of profiled sheets are suitable for roofing, although visually they may appear similar. The main difference lies in the height of the corrugation and the presence of additional stiffening ribs, which give the sheet the ability to withstand loads.
The second most important parameter is the thickness of the metal. A thin sheet (less than 0.45 mm) is easily deformed when walking during installation or under the pressure of snowdrifts. The optimal solution for a private garage is considered to be metal with a thickness of 0.5 mm, which provides a balance between price and strength.
- 🏗️ Corrugation height: for the roof, a wave height of 20 mm is recommended, which ensures sufficient rigidity.
- 🛡️ Coverage type: the protective layer must be resistant to ultraviolet radiation and mechanical damage.
- ⚖️ Structure weight: light corrugated sheeting does not require reinforcement of the rafter system, unlike heavy materials.
It is also important to consider the angle of inclination of the slope. The higher it is positioned, the higher the corrugation should be to ensure efficient water flow and eliminate the risk of leaks. For flat roofs, the use of corrugated sheeting requires special sealing of joints and is often not recommended without professional calculations.
When ordering corrugated sheeting, always add 10-15% to the estimated area for trimming and overlaps to avoid material shortages in the midst of work.
Analysis of popular brands: C8, C21, NS35 and others
There are many brands on the building materials market, but for garages several basic options are most often considered. Brand C8 is a classic wall profile with a wave height of 8 mm. Although some people use it for high-angle roofs, it is a risky choice for a garage due to its low load-bearing capacity.
A more reliable option is S21. This brand is already considered universal and is often used for roofing pitched roofs. The wave height of 21 mm allows the sheet to better resist wind loads and snow. This is the “golden mean” for budget construction.
If your garage is located in a region with heavy snowfall, you should take a closer look at the brand NS35 or H60. These profiles have a pronounced trapezoidal shape and additional grooves that act as stiffeners. Such a sheet will withstand the weight of a person when servicing the roof and heavy snow cover.
⚠️ Attention: Using the C8 brand for a single-pitched garage roof is strictly not recommended without continuous sheathing, as there is a high risk of the sheet sagging between the slats.
When choosing between brands C21 and HC35, budget often becomes decisive. However, the difference in price can be offset by the service life and lack of need for repairs after a couple of years. The supporting profile will last longer in aggressive external environments.
Metal thickness and type of polymer coating
The durability of the roof directly depends on the quality of the protective layer and the thickness of the steel base. The standard galvanizing thickness must be at least 140 g/m², which corresponds to the first class of galvanizing. A smaller amount of zinc will lead to rust after 3-5 years of use.
The polymer coating performs decorative and additional protective functions. The cheapest option is polyester (PE), which withstands temperature changes well, but is easily scratched. More expensive matte polyester (MPE) hides minor installation defects and looks more noble.
- 🎨 Polyester (PE): glossy surface, thickness 25 microns, budget option with a service life of up to 20 years.
- 🌫️ Matte polyester (MPE): thickness 35 microns, high resistance to fading and corrosion, imitates texture.
- 🛡️ Pural: premium polyurethane-based coating, resistant to scratches and chemicals, service life over 40 years.
For a garage, which is often an unheated space, the elasticity of the coating is critical. When the metal cools suddenly, it shrinks, and if the polymer is brittle, it can develop microcracks, opening the way for corrosion. Therefore, in cold regions it is better to overpay for high-quality coating than to change sheets every decade.
The best choice in terms of price/quality ratio for a garage is 0.5 mm thick corrugated sheeting coated with matte polyester (35 microns).
Calculation of the amount of material and components
Correct calculation of the material will allow you to avoid unnecessary costs and downtime. First you need to measure the area of the slopes, taking into account the overhangs of the cornice. Usually the overhang is about 20-30 cm to protect the walls from rain.
In addition to the sheets themselves, you will need additional elements. The ridge will cover the top edge of the roof, the end strips will protect the edges from the wind, and the eaves strip will direct water into the gutter or simply neatly form the overhang. Self-tapping screws must be purchased with a rubber EPDM washer that will not dry out in the sun.
| element | Purpose | Installation features |
|---|---|---|
| Horse | Protection of the upper junction of the slopes | Attached to the top wave through the sheet |
| Self-tapping screws | Fastening sheets | Screwed strictly perpendicularly into the lower wave |
| Sealant | Sealing under the ridge | Follows the wave profile, prevents birds from getting hit |
| Wind bar | End protection | Covers the end of the sheathing and the edge of the sheet |
The number of self-tapping screws is calculated based on a consumption of approximately 6-8 pieces per square meter. You should not skimp on fasteners: cheap self-tapping screws without a magnetic head or with bad rubber will become the weak link of the entire structure. It is better to immediately take fasteners in the color of the corrugated sheet.
Preparing the sheathing and base for installation
The quality of the base under the corrugated sheet determines the evenness of the roof and the absence of deflections. For a garage, sparse sheathing made from edged boards or timber is most often used. The pitch of the sheathing depends on the angle of inclination: the smaller it is, the more often the boards should lie.
If the slope angle is less than 15 degrees, it is recommended to make a continuous sheathing from moisture-resistant plywood or OSB board. This will prevent the metal from being pressed through and provide additional waterproofing. The tree must be treated with an antiseptic and fire retardant.
☑️ Preparation for installation of corrugated sheets
A waterproofing film must be laid under the corrugated sheeting, even if the garage is not residential. It will protect the internal space from condensation that forms on the back side of the metal during temperature changes, and from possible minor leaks. The film should have a sag of about 2 cm between the rafters.
⚠️ Attention: Never install corrugated sheeting directly on the rafters without lathing and counter-latching - this will lead to rapid rotting of the wood and corrosion of the metal due to lack of ventilation.
Laying technology and typical mistakes
Installation of sheets begins from the bottom row. The sheets are laid with an overlap in one or two waves (depending on the brand and angle of the roof). It is important to align the first sheet with the cornice, as it sets the direction for the entire row. Fastening is carried out with special roofing screws.
The most common mistake is overtightening or undertightening the screws. If you overtighten, the rubber washer will burst or become wrinkled, and water will flow into the hole. If you don’t tighten it enough, the sheet will dangle and the wind will tear off the seal. The washer should fit tightly to the metal, slightly deforming.
When working on the roof, you need to walk only in soft shoes, stepping into the lower part of the wave (into the hollow), where the sheet lies on the sheathing. You cannot step on the crest of the wave - this will lead to deformation of the profile and disruption of the geometry of the sheet.
What to do if you need to cut corrugated sheeting on the roof?
You cannot use a grinder with an abrasive disc - it burns out zinc and polymer, triggering corrosion. Use only electric metal scissors or a special scissor attachment on a drill/grinder.
The final stage is the installation of additional elements. The ridge is attached through the wave to the ridge; it is advisable to place a sealing tape under it. The end strips are mounted with self-tapping screws of 30-40 cm. After installation, it is advisable to walk along the roof and check all the joints.
Comparative table of corrugated sheet characteristics
To make a final determination and choice, it is convenient to use a summary table that shows the differences in the parameters of the main brands applicable for garage construction.
| Parameter | S8 (Wall) | C21 (Universal) | NS35 (Carrying) | H60 (Carrying) |
|---|---|---|---|---|
| Wave height, mm | 8 | 21 | 35 | 60 |
| Recommended lathing pitch | Solid | Up to 650 mm | Up to 1200 mm | Up to 3000 mm |
| Snow load | Low | Average | High | Very high |
| Cost per m² | Low | Average | High | High |
As can be seen from the table, for most standard garages with a rafter pitch of 60-80 cm, the optimal choice is C21. It is cheaper than load-bearing brands, but much stronger than wall C8. If the garage has a large area or is located in a snowy region, switching to HC35 will be a wise investment.
Is it possible to put corrugated sheets on a flat garage roof?
Technically it is possible, but this requires creating an artificial slope using expanded clay or screed, as well as using a grade of at least H60 with careful sealing of all joints. For flat roofs, rolled fused materials or membranes are more often used, since they are more reliable in a horizontal position.
What color of corrugated sheeting is better to choose for a garage?
From a practicality point of view, dark colors (brown, green, blue) are less dirty from dust and look more noble against the background of the garden. Light shades (white, beige) better reflect the sun's rays, which is important if the garage is metal and gets very hot inside in the summer.
Is it necessary to process sections of corrugated sheets?
Yes, this is critical. When cutting a sheet with scissors or a saw, the integrity of the zinc and polymer layers on the edge is violated. The cut must be painted with a special anti-corrosion paint for metal in the color of the coating to prevent rust.
Can you hear rain through a corrugated roof?
Yes, the sound of pattering rain is quite strong. To reduce noise, it is necessary to install high-quality heat and sound insulation. A layer of mineral wool or foam plastic, laid between the rafters under the corrugated sheet, completely dampens the noise of precipitation.