At the initial stage of constructing a townhouse, the foundation structure is the most crucial part. Only with a solid foundation can a multi-story house be safely built without subsidence or collapse.
The foundation not only directly affects the building itself but also impacts surrounding structures. Poor foundation handling can lead to unforeseeable consequences for both the homeowner and neighboring areas.
Therefore, investors must clearly understand the technical factors, structural design, and practical construction experience required for proper execution.
Subgrade Concrete
Subgrade Concrete
This layer is located beneath the foundation concrete, tie beams, and structural elements that come into contact with the soil. The primary function of the subgrade concrete is to:
- Level the foundation pit surface
- Prevent moisture loss from the concrete layer above
- Reduce soil deformation caused by external forces
- Protect the reinforced foundation concrete
Formwork for Foundations and Tie Beams
Foundation and tie beam formwork typically comes in two types: plywood formwork and brick wall formwork. While both serve the function of shaping the structure, their inspection methods differ.
- Brick wall formwork:
- Must be aligned straight and built firmly to prevent collapse when pouring concrete.
- The brick walls should be sealed tightly to minimize water loss from the concrete.
- Plywood formwork:
- First, the wooden panels must be cleaned before use.
- The thickness of the plywood determines the required support system.
- This type of formwork is easier and quicker to install but is also more prone to collapse, requiring strong reinforcement.
Ensuring proper formwork installation is essential to maintaining structural integrity. A well-aligned foundation and tie beam prevent misalignment of steel reinforcement and ensure accurate concrete volume, avoiding unnecessary shortages. Additionally, it reflects the skill level of construction workers.
Steel Reinforcement
The steel reinforcement must meet quality standards and match the agreed specifications in the construction contract. Since the foundation is the core of structural stability, high-quality steel should be used, such as Vietnam-Japan steel.
Incorrect steel placement not only wastes materials but also poses a risk of subsidence, cracking, or collapse over time. Therefore, rigorous inspection is essential.
Steel Reinforcement Inspection Criteria:
- Must comply with technical building standards and be of certified quality.
- Structural steel must match the pre-approved design drawings calculated by engineers.
- Steel bars must be arranged in straight, orderly rows; primary and secondary bars must not overlap haphazardly.
- The steel must be clean and free from rust.
- The anchoring length of the reinforcement should meet the technical requirement, typically 30-40 times the diameter of the bar.
Concrete Pouring
After completing thorough surface cleaning and steel inspection, proceed with foundation and tie beam concrete pouring.
Concrete is categorized into two types:
- Manually mixed concrete
- Commercial ready-mix concrete
Regardless of the type, quality control is essential before pouring.
- For manually mixed concrete:
- Inspect the quality of sand, gravel, cement, and water.
- Ensure proper material quality and correct mixing ratios.
- For commercial concrete:
- Verify the factory delivery certificate and the concrete volume.
- Conduct sample collection and slump testing before use.
A critical step during concrete pouring—regardless of the type—is using specialized vibration equipment to compact the concrete and ensure structural integrity.
Concrete Curing
Many people overlook the curing process, assuming it is unnecessary. However, this is a misconception. Improper curing can lead to cracks, reduced structural lifespan, and weakened durability.
Once the concrete has set and hardened, the curing process should begin.
Concrete Curing Methods:
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Water curing: Regularly spray water onto the concrete surface to maintain moisture.
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Covering method: Use plastic sheets or wet burlap to retain humidity and prevent moisture loss.
Proper curing ensures long-term structural strength and enhances the durability of the foundation.
