Installation metal garage - this is not just buying and assembling a box from corrugated sheets or sheet iron. This is a complex engineering process that begins long before the first truck with materials arrives. Many car owners make the fatal mistake of thinking that a lightweight structure can be placed directly on grass or lightly compacted sand. In practice, this leads to misalignment of the gate, deformation of the frame and the rapid formation of condensation, which will destroy your car in a couple of seasons.
Correct foundation preparation - this is the foundation (literally and figuratively) of the durability of your structure. The soil under the structure behaves unpredictably: it swells in winter, is washed away by spring meltwater, and sags under load. If you do not take these factors into account, even the most expensive garage-shell will turn into a pile of scrap metal. In this article we will analyze all stages of site preparation, from choosing a location to final leveling.
It is important to understand that a metal garage, unlike a brick or concrete one, has its own characteristics. It is lighter, but at the same time more sensitive to ground movements. Frame geometry must remain perfect so that the gate leaves close tightly. Any distortion of the corners will lead to the fact that in winter you simply will not be able to get inside, as the doors will jam. Therefore, the approach to site preparation must be professional and thorough.
Choosing the optimal location on the site
The first step is not digging the earth, but analyzing the territory. Terrain plays a key role. The ideal option would be a flat area, but if your site has a slope, it will have to be leveled. Don't try to fit a garage into a difficult landscape without excavation work - this will save money now, but will require huge investments in structural repairs later.
Please note groundwater level. If in the spring there are puddles in the chosen place, it means that the water comes close to the surface. In this case, installing a metal garage without a serious drainage system and raising the floor level is strictly not recommended. Moisture will constantly attack the metal from below, causing corrosion, and dampness will reign inside.
⚠️ Attention: Never install a metal garage in a low area where water flows from the slopes of the roof of the house or neighboring buildings. Constant flooding of the foundation will destroy any waterproofing in one season.
Also worth considering access roads. The car not only needs to drive into the garage, but also, possibly, turn around or back up. If the space is too narrow, you run the risk of scratching the sides on gates or walls every day. Plan your maneuver area in advance by clearing it of bushes and trees.
Cleaning the area and removing the fertile layer
After choosing a location, the physical work begins. First of all, the area must be completely cleared of vegetation. Grass, roots of trees and shrubs are not just garbage, they are an active biological environment. The roots will grow, destroying the prepared base, and the organic matter, rotting under the floor, will create voids and release moisture.
Removal fertile layer (turf) is a mandatory procedure. Usually the top 15-20 cm of soil is removed. This is done for several reasons. Firstly, fertile soil is rich in organic matter, which rots over time, causing subsidence. Secondly, this soil is full of seeds and roots that will grow through any covering if they are not removed.
To do this job you can use excavator or mini loader, if the area is large, but for a standard single garage, manual work with a shovel is often sufficient. The main thing is to remove the soil evenly over the entire area of the future building with a margin of 50 cm on each side for ease of work.
- 🚜 Remove the entire plant layer to the depth of a spade bayonet.
- 🌳 Remove all tree roots and large stones.
- 📏 Mark the perimeter with a reserve for drainage and blind area.
- 🗑️ Take out the removed soil or distribute it around the garden.
After removing the soil, the surface must be carefully leveled and compacted. For this purpose it is used vibrating plate or hand tamper. A dense base is necessary so that the cushion of sand and crushed stone does not go deep into the soft earth. If the soil is clayey, special attention should be paid to tamping, since clay is prone to heaving.
Drainage system design
Water is the main enemy of a metal garage. Even if the groundwater is deep, precipitation can cause problems. Device drainage system around the perimeter of the garage allows you to remove excess moisture and keep the interior dry. This is especially true for regions with heavy rainfall and snowmelt.
There are two main types of drainage: surface and deep. For a metal garage, a combination of surface drainage and wall drainage is most often sufficient. A trench is dug around the prepared pit or site into which the drainage pipe, wrapped in geotextile. The pipe must have a slope towards the water intake or storm sewer.
How to check the need for deep drainage?
Dig a hole 1.5-2 meters deep where the garage will be installed. If water appears at the bottom within 24 hours, then the groundwater level is high and you will need a serious drainage system or choose a different location.
Crushed stone is poured over the pipes, which serves as a filter. It is important not to confuse crushed stone with sand when backfilling a trench. Crushed stone does not silt up as quickly as sand and provides better water flow. The drainage is covered from above with a layer of geotextile to prevent soil from getting into the system.
| Drainage type | Laying depth | Material | Purpose |
|---|---|---|---|
| Superficial | 10-30 cm | Trays, pipes | Rainwater drainage |
| Wall-mounted | Foundation base level | Perforated pipes | Groundwater protection |
| Plast | Under the entire slab | Crushed stone, geotextiles | Decreased moisture levels |
| Trench | Below freezing | Drainage pipes | Drainage of water from the site |
If you ignore drainage on wet ground, you are creating a "bathtub" under your car. The water will evaporate, increasing the humidity inside, which will lead to corrosion of the car body and the garage itself. Capillary rise moisture through a concrete floor is a real problem that can only be solved by proper waterproofing and drainage.
Selection and preparation of the foundation
A metal garage is not a heavy structure, but this does not mean that it does not need a foundation. On the contrary, for lightweight structures the requirements for foundation rigidity are often higher, since they cannot compensate for ground movements with their mass. There are several types of foundations suitable for metal hangars.
The most popular and reliable option is considered monolithic slab. It serves as both a foundation and a floor. The slab distributes the load evenly over the entire area, which prevents local subsidence. The thickness of such a slab is usually 10-15 cm, but for severe operating conditions or installation of an inspection pit, reinforcement may be required.
☑️ Preparation for pouring the foundation
An alternative could be strip foundation. It is cheaper in terms of concrete consumption, but requires a separate floor installation. The tape is good on stable soils where strong movements are not expected. However, for a metal garage, where tightness around the perimeter is important, a slab is still preferable.
⚠️ Attention: When pouring the foundation, be sure to use reinforcement cage. Even for a lightweight structure, the lack of reinforcement will lead to cracks in the concrete at the first frost, which will compromise the integrity of the floor.
Before pouring concrete, it is necessary to lay waterproofing. Usually thick polyethylene film or roofing felt is used. It is laid on top of a sand cushion. This prevents moisture from leaving the concrete solution into the ground and protects the future floor from capillary moisture. The quality of waterproofing directly affects the microclimate inside the garage.
Installation of sand and crushed stone cushion
The foundation of any good foundation is a properly prepared cushion. It performs two functions: drainage and shock-absorbing. Sand-crushed stone mixture (PGS) or separate layers of sand and crushed stone make it possible to compensate for soil movements and drain water from the base of the foundation.
The installation technology is simple, but requires consistency. First, a layer of coarse crushed stone (fraction 20-40 mm) is poured, which is compacted. Then comes a layer of sand (preferably river sand, which does not contain clay). The total thickness of the cushion can vary from 20 to 40 cm depending on the type of soil.
Use geotextiles between the cushion layers and the soil. This will prevent the sand from mixing with the ground and silting of the drainage layer, preserving its properties for decades.
Each layer must be shed with water and compacted thoroughly. Vibrating plate indispensable here. If compaction is poor, the cushion will sag over time, dragging the concrete slab with it. You can check the quality of the tamping in a simple way: when you step on the surface, you should not leave a deep mark.
It is important to consider that the sand must be clean. The presence of clay inclusions is unacceptable, since clay retains water and expands when freezing, causing frost heaving. If you use ready-made ASG, make sure of its quality, or it is better to purchase materials separately.
Waterproofing and insulation of the base
Metal has high thermal conductivity, so temperature changes inside the garage occur very quickly. To reduce the formation of condensation and make staying in the garage comfortable, the base is often insulated. Extruded polystyrene foam (XPS) is an ideal material for laying under a concrete slab.
Sheets of insulation are laid on top of the waterproofing in two layers with overlapping joints. This creates a continuous thermal circuit, cutting off the cold from the ground. Insulation is especially important if you plan to use the garage as a workshop or store temperature-sensitive materials there.
Waterproofing also requires attention. In addition to the film under the stove, it is worth doing cut-off waterproofing along the perimeter so that moisture does not rise along the ends of the slab. To do this, the edges of the waterproofing material are released outward and subsequently pressed against structural elements or a blind area.
The combination of XPS insulation and high-quality waterproofing under the slab reduces energy loss and prevents dampness, extending the life of the car and the garage itself.
Don't skimp on waterproofing materials. Cheap films can tear when installing fittings. It is better to use specialized membranes or dense polyethylene with a thickness of at least 200 microns. The tightness of this layer is the key to a dry floor.
Final alignment and preparation for installation
After the concrete has gained strength (usually 28 days to complete, but 7-10 days to start work is enough), you can begin the final stage. The surface of the slab must be perfectly flat. The presence of bumps or holes will make it difficult to install the garage frame. Horizontal checked with a laser level or a long rule with a bubble level.
If irregularities are found, they can be eliminated using self-leveling mixture or cement screed. The height difference should not exceed 2-3 mm per 2 meters of length. This is critical to ensure that the bottom of the garage fits tightly to the foundation.
Before installing the garage, it is recommended to mark the perimeter of the slab. This will help accurately position the structure. Also at this stage are mounted embedded parts or an anchor, if the garage design provides for a rigid connection to the foundation. In windy regions this is a mandatory safety requirement.
- 📏 Check the diagonals of the site - they must be equal.
- 🧹 Clean the stove surface from dust and debris.
- 🔩 Install anchor bolts according to the garage drawing.
- 💧 Treat the ends of the concrete with a water repellent.
Only after careful preparation of the site can you order delivery and installation of the garage itself. Proper preparation will take time and require investment, but it will ensure that your metal garage will last for decades, protecting your vehicle rather than requiring constant repairs.
Is it necessary to make an inspection hole in a metal garage?
It is possible to make an inspection hole in a metal garage, but it requires a special approach. The pit must be made of monolithic concrete with high-quality waterproofing, since the metal of the garage does not protect against ground moisture as well as a permanent structure. In addition, the groundwater level must be low. It is often easier and more efficient to use a mobile overpass, which can be taken outside if necessary.
Is it possible to install a metal garage in winter?
Installation of the structure itself is possible at any temperature, but site preparation (earthwork, concreting) in winter is extremely difficult or impossible without special additives and heating of the concrete. It is better to prepare the site in the fall, before the onset of frost, so that you can immediately install the garage in the spring.
How to protect a metal garage from lightning?
A metal garage is an excellent conductor and target for lightning. If it is located separately from the house, it is recommended to install a lightning rod. Grounding the structure is also a mandatory electrical safety requirement, especially if electrical wiring is installed inside the garage.