Every motorist sooner or later faces the need to look under the bottom of his vehicle for diagnostics or minor repairs. Having your own overpass or observation pit in the garage greatly simplifies this process, saving time and money on the services of service centers. However, in order for the design to be safe and durable, a competent flyovertaking into account all loads and features of the soil.
In this article, we will discuss in detail the stages of design, selection of materials and direct construction. You will learn how to calculate the sizes correctly. passenger-car Or the SUV was freely placed on the ramp, and what nuances of waterproofing can not be ignored. Creating a high-quality drawing is the foundation without which it is impossible to build a reliable structure.
Before starting excavation work, it is necessary to determine the type of design. This can be a full-fledged observation pit, mini-overpass or combined version. Dimensions of flyovers It depends on the model of your car and the size of the garage. Errors in the planning phase can make repair work impossible or, worse, the structure collapses under the weight of the machine.
Selection of design type and calculation of dimensions
The first step in creating a drawing is to determine the type of lift. For a garage, you most often choose between a classic observation pit, which is below the floor level, and a ground overpass. Ground construction requires less earthwork, but takes up more usable space. Overpass calculation The height of the garage ceiling should be taken into account so that the driver can work comfortably without hitting his head.
The width of the working area is determined by the track of the car. The standard width for passenger cars is about 1500 mm, but for versatility it is better to lay 1800-2000 mm. The length of the working part should allow you to place the entire body, but for convenience often make a length of 4-5 meters, which allows you to drive the car with a margin. Height of the flyover Usually ranges from 1500 to 1800 mm, which provides sufficient clearance for lying down operation.
- 🚗 Routine width: The minimum width of the race should be 30-40 cm more than the track of the widest car.
- 📏 Length of ramp: The optimal length for a comfortable ride is at least 3 meters with a slope of no more than 15-20 degrees.
- 🚙 Safety margin: the design must withstand the weight of the car with a margin of at least 2 times the maximum weight.
⚠️ Note: When designing, consider not only the current car, but also the possibility of buying a larger SUV or minivan in the future. Saving space now could be a problem in a few years.
An important parameter is the angle of entry. Too steep a lift can lead to damage to the bumper or a decrease in clearance at the time of arrival. If you are building a ground overpass, the length of the upper section (the ramp) should be sufficient for a smooth climb. In the drawings, this element is often referred to as runway It requires special attention to the reinforcement.
Required materials and tools
For the construction of a reliable overpass requires high-quality building-material. The basis of the design is concrete, reinforcement and materials for waterproofing. The use of cheap cement or small diameter reinforcement can lead to cracks and destruction of walls under soil pressure. Concrete must be grades not lower than M250 (B20) to ensure the necessary strength.
In addition to basic materials, you will need a set of tools. To work with metal, a welding apparatus, a Bulgarian and measuring devices will be required. If it is planned to arrange an observation pit with brick or block walls, a master, level and container for the solution are necessary. Waterproofing materials They are selected depending on the level of groundwater in the area.
☑️ List of required materials
Particular attention should be paid to the choice of valves. For the formation of the frame of walls and floor, a rod fitting of class AIII (A400) with a diameter of 10–14 mm is used. Bundle of elements is better to produce knitting wire, since welding can weaken the metal at the joints. For formwork, trimmed boards with a thickness of 25-40 mm or moisture-resistant plywood will suit.
Design stages and drawing creation
Creating a detailed drawing is a key step that should not be missed. On paper or in specialized software, it is necessary to display all dimensions: length, width, height, thickness of walls and floor. Overpass scheme shall include incisions showing the position of the reinforcing layers and the waterproofing. This will help to avoid errors in the installation of formwork and pouring concrete.
The drawing also indicates the places for niches. Niches in the walls of the observation pit are designed for storing tools, lamps and spare parts. Their location should be convenient, but not violate the integrity of the supporting structures. The depth of niches is usually 200-300 mm, and the height depends on the type of items stored.
| Parameter | Minimum value | Optimal value | Commentary |
|---|---|---|---|
| Breadth of passage | 2000 mm | 2500 mm | Stock accounting for different cars |
| Length of work area | 4,000 mm | 5000 mm | Comfort for long cars |
| Ceiling height | 1800 mm | 2000 mm | Standing up for work |
| Thickness of walls | 150 mm | 200 mm | Depends on the ground. |
When designing, take into account the need to install stops for wheels (blowers). They prevent the car from slipping off the overpass. In the drawing, these elements are indicated as wheel-off They are located on the ends of the lifting paths. The height of the breaker shall be at least 100 mm.
Preparation of the pit and foundation
Construction begins with the marking of the territory and digging the pit. The dimensions of the pit in the plan should exceed the dimensions of the overpass by 30-50 cm on each side for the convenience of installing formwork and laying waterproofing. The bottom of the pit is carefully tamped and filled with a layer of sand and rubble, which serves as a drainage cushion. Flyover foundation takes on the main load, so you can not save on the preparation of the base.
After laying the pillow (usually 10 cm of sand and 10 cm of rubble), the rough floor is filled. For this purpose, a concrete mixture of the M200-M250 brand is used. The thickness of the floor is 100-150 mm. Before pouring, a layer of waterproofing is necessarily laid to prevent capillary moisture rise from the soil. Concrete flooring It should be carried out in one step for the monolithic design.
- 🚜 Earthworks: When digging the pit, monitor the condition of the walls to avoid falling soil.
- 💧 Drainage: At the bottom of the pit, provide a water collection pit with a pump for pumping it.
- 🧱 Reinforcement: the grid of rebar on the floor should be raised above the rubble by 3-5 cm for proper distribution in concrete.
If the groundwater level is high, a more complex drainage system around the pit may be required. In such cases, it is recommended to make external coating waterproofing of walls after their construction. It is critical to ensure the tightness of the joint between the floor and walls, as this is the most vulnerable place for leaks.
Wall construction and reinforcement
The walls of the observation pit can be made of concrete blocks, bricks or by the method of monolithic concreteting. Monolithic construction is considered the most durable and durable. For her, a formwork is assembled from boards, inside which a reinforcement frame is mounted. Wall reinforcement is produced in two layers with a step of cells 150-200 mm.
The walls are also filled with concrete of the brand not lower than M250. It is important to vibrate the mixture carefully when pouring to remove air bubbles and ensure the density of the structure. Formwork can be removed in 7-10 days, but the full strength of the concrete will gain only after 28 days. Monolithic walls It is better to resist the pressure of the soil than the masonry of blocks.
⚠️ Note: When pouring high walls (more than 1.5 meters), it is not recommended to pour the entire volume at once. Pause or use a phased pour to avoid breaking the formwork under the pressure of liquid concrete.
In the process of reinforcement, do not forget to lay the embedded parts for fastening shelves, lighting and ventilation. If you use blocks, be sure to do vertical reinforcement every 3-4 rows. This will give the masonry the necessary stability and strength to break.
Waterproofing and finishing
Protection from moisture is the key to a long service overpass. Even if groundwater is deep, seasonal precipitation can saturate the soil. For waterproofing, bitumen mastics, roll materials (ruberoid, glassisol) or penetrating compositions are used. Waterproofing of the flyover It is applied to the outside of the walls after removing the formwork or is superimposed in the masonry process.
After drying waterproofing, the sinuses between the wall and the ground are reversed. The earth should be covered with layers of 15-20 cm with mandatory tamping. This will prevent soil from subsidence around the pit in the future. The inside of the pit can be plastered or tiled to improve lighting and ease of cleaning.
For lighting, it is better to use low-voltage lamps (12V or 36V) with a moisture-proof housing. The sockets and switches shall be located outside the observation area. Quality finishing Turn the garage pit into a comfortable workplace.
Frequently Asked Questions (FAQ)
Which brand of concrete is better to use for the overpass?
The best choice is concrete of the grade M250 (class B20) or M300 (class B22.5). These brands provide the necessary strength and frost resistance. The use of lower grades, such as the M150, is only possible for light soils and low loads, but the savings in this case are risky.
Do I need to waterproof if the groundwater is deep?
Yes, waterproofing is necessary anyway. Groundwater can rise in the spring or after heavy rains. In addition, waterproofing protects concrete from aggressive chemicals contained in the soil, prolonging the life of the structure.
Can a metal frame be used instead of concrete walls?
Yes, you can make a flyover from a metal channel and a corner. Such structures are faster in installation, but require high-quality anticorrosion treatment. Metal overpasses are often made ground-based, as they do not require complex waterproofing of the pit.
How to calculate the angle of inclination of the entrance ramp?
The angle of inclination should not exceed 15-20 degrees (about 25-30% of the slope). To calculate the length of the ramp, use the formula: Length = Height of lift / tan (angle). For a height of 1.5 m and an angle of 15 degrees, the length of the ramp will be about 5.6 meters. A ramp that's too steep is dangerous for a ride.