How to make a foundation: step-by-step instructions, types, and useful tips

The foundation is the basis of any building. The overall stability of the structure, its durability, and safety depend on its strength and reliability. A common question arises: how to make a foundation? In this article, we will detail the main types of foundations and provide step-by-step recommendations that will help you carry out the work correctly. We will pay special attention to popular queries: how to make the layout of the foundation, formwork, waterproofing, concrete mix, and we will also discuss how to make a foundation for a garage.

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1. Main types of foundations

The choice of foundation type is determined by the size of the building, soil characteristics, and operating conditions. Let’s consider several of the most common options:

1.1 Strip (beam) foundation

• Features: The most common due to its relatively simple technology and acceptable price. It consists of a continuous reinforced concrete “strip” laid under all load-bearing walls of the house.
• Where it is used: For the construction of private houses, cottages, garages, and outbuildings with moderate loads.
• Advantages:
  • Relatively low cost
  • Simplicity of installation
• Disadvantages:
  • Requires a significant amount of earthworks
  • Not always suitable for sites with complex terrain

Note: In some sources, the term “beam foundation” is encountered, but the term “strip” is most commonly used.

1.2 Slab foundation

• Features: It consists of a solid reinforced concrete slab located on a prepared cushion (sand-gravel mixture).
• Where it is used: For massive and heavy houses (with concrete or stone walls), as well as in areas with weak or unstable soil.
• Advantages:
  • High resistance to uneven subsidence
  • Can be used on problematic soils
• Disadvantages:
  • Relatively high consumption of concrete and reinforcement
  • Higher costs for foundation preparation

1.3 Column foundation

• Features: Consists of separate columns (made of concrete, brick, metal, or wood) connected by a beam (horizontal bar).
• Where it is used: Under light frame buildings, gazebos, terraces, or outbuildings on uneven sites.
• Advantages:
  • Less concrete volume compared to strip foundations
  • Less earthworks
• Disadvantages:
  • Not suitable for heavy houses
  • Requires careful protection against soil freezing

1.4 Pile (deep) foundation

• Features: Reinforced concrete, metal, or wooden piles are driven or screwed into the ground to transfer the load to deeper layers.
• Where it is used: On weak soils, peat bogs, areas with high groundwater levels, or significant terrain variations.
• Advantages:
  • Can be used even on very problematic soils
  • Reduction of earthworks volume
• Disadvantages:
  • Complexity and cost of installation (often requires special equipment)
  • Requires precision in execution

1.5 Surface foundation

• Features: Formed from a small excavation or is laid directly on the ground using special pads and beams.
• Where it is used: For very light buildings (warehouses, temporary structures) and only on dense and stable soils.
• Advantages:
  • Low cost
  • Speed of installation
• Disadvantages:
  • Suitable only for light structures
  • Prone to frost heave and other soil deformations

2. Stages and tips for building a foundation

Regardless of the chosen type of foundation, there are general steps to follow:

2.1 Foundation layout (site preparation)

1. Site clearing: Remove vegetation, stones, debris, and other obstacles.
2. Leveling the terrain: If necessary, remove the top layer of soil or add fill to reduce slopes.
3. Marking:
   • Use stakes and string to mark the outlines of the future foundation.
   • Check the diagonals of rectangles or squares to ensure the corners are right angles.
   • For accuracy, use a construction level and tape measure.

Life hack: To simplify the foundation layout, use the Pythagorean theorem (checking diagonals) or laser levels.

2.2 Earthworks and excavation

1. Excavation: The depth depends on the type of foundation and the frost depth in your region. For a strip foundation, it is usually 0.5–1.5 m.
2. Foundation preparation:
   • Sand-gravel cushion (10–20 cm) for drainage and leveling.
   • Compaction of the cushion (using a vibratory plate or manual tamper).

2.3 How to make formwork for the foundation

1. Material selection: Boards with a thickness of 25–40 mm or plywood sheets (water-resistant) are most commonly used.
2. Formwork installation:
   • Secure the formwork panels with stakes or special supports from the outside.
   • Check verticality using a level.
3. Sealing joints: To prevent concrete from leaking, joints can be taped with construction tape or foamed.

Tip: The formwork must withstand the weight of the concrete, so it is better to provide additional braces.

2.4 How to make concrete for the foundation and reinforcement

1. Concrete preparation:
   • Composition of classic concrete: cement (M400 or M500), sand, gravel (fraction 5–20 mm), water.
   • Proportions: approximately 1:2:3 (cement : sand : gravel) plus water to the desired consistency (not too liquid!).
   • You can order a ready mix from a concrete truck – this will save time and improve quality.
2. Reinforcement:
   • Use metal reinforcement with a diameter of 8–16 mm (depending on calculations).
   • Tie the rods with wire or use plastic ties.
   • For strip foundations, usually two or three horizontal rows of reinforcement are made with a step of 15–20 cm.

2.5 Pouring the foundation

1. Gradual pouring: Pour concrete in layers of 20–30 cm.
2. Vibration and compaction: Use a deep or surface vibrator to remove air bubbles.
3. Leveling the top layer: Use a rule or trowel for a smooth surface.

2.6 Care for concrete

1. Moistening: In the first few days, it is advisable to moisten the concrete with water, especially in hot weather.
2. Covering: Cover the surface with polyethylene film or tarpaulin to avoid rapid evaporation of moisture.
3. Curing time: The initial strength gain lasts 7–14 days. Full strength is achieved in about 28 days.

2.7 How to make waterproofing for the foundation

1. Horizontal waterproofing: Before laying walls on the foundation, be sure to lay roll waterproofing (roofing felt, hydroisol, etc.).
2. Vertical waterproofing:
   • Apply coating or bitumen-polymer materials to the outer walls of the foundation.
   • For additional protection, you can use torch-on roll materials.
3. Drainage system: To divert groundwater, install perforated drainage pipes around the perimeter of the foundation and ensure they lead to a drainage well.

3. How to make a foundation for a garage

Building a foundation for a garage has its own peculiarities:

1. Determining the load: If the garage is intended for a passenger car, a strip foundation with a depth of 60–80 cm is usually sufficient. For heavier structures or garages with a second floor, a slab foundation may be required.
2. Ease of access: Leave space for entry, considering the height of the foundation and the floor level.
3. Waterproofing: Since garages often come into contact with moisture (rain, snow on wheels), it is worth paying special attention to waterproofing work on the floor and around the perimeter of the walls.
4. Ventilation: Provide openings or channels to prevent moisture from accumulating in the room.

4. Additional tips for the strength and durability of the foundation

1. Quality materials: Do not skimp on cement and reinforcement, as the reliability of the entire structure depends on this.
2. Proper formwork: Ensure that it does not deform during the pouring of concrete.
3. Level control: During the pouring of the foundation, check the horizontality of the top layer.
4. Reinforcement extensions: If the foundation is to be poured in parts or you plan to install monolithic reinforced concrete ceilings, leave reinforcement extensions for reliable connection.
5. Insulation: If you are building a house for permanent residence, provide thermal insulation for the foundation (for example, with extruded polystyrene) to protect against frost heave and retain heat.
6. Timely care for concrete: Do not neglect watering and covering the foundation in the first week to a week and a half, as this significantly affects the quality and strength of the concrete.

5. Conclusion

Building a foundation is a key stage in the construction of any building, whether it is a house, cottage, or garage. To ensure the reliability and durability of the structure, it is necessary to correctly determine the type of foundation, perform quality layout, ensure proper formwork, prepare suitable concrete and reinforcement, as well as carry out waterproofing. Adhering to construction standards, using quality materials, and careful control of all stages of work are the keys to a strong and safe structure.

We hope that the tips and recommendations provided here will help you understand how to make a foundation correctly and avoid common mistakes. If you have any doubts, it is better to consult professionals, as correcting mistakes in the foundation always costs much more than building “from scratch” according to all the rules.

May your foundation serve as a strong support for many years!