How are slab foundations built?

Site Preparation

The first step in building a slab foundation is preparing the site. This phase is crucial as it sets the groundwork for everything that follows. The preparation involves clearing the land of any debris, vegetation, or existing structures that might interfere with the construction. This step ensures that the site is clean and ready for excavation.

Excavation

Once the site is prepared, excavation begins. The goal here is to create a level surface that matches the dimensions needed for the foundation. The depth of the excavation depends on several factors, including the soil type and the load-bearing capacity required by the building. It is also influenced by local building codes that dictate specific requirements based on geographic and environmental considerations. Excavation must be done carefully to ensure that the foundation will sit on stable soil that can support the weight of the structure.

Installation of Formwork

After excavation, formwork is installed. Formwork consists of temporary moulds made from wood or steel that hold the poured concrete in place while it sets. The formwork is designed according to the architectural plans and provides the shape and dimensions of the foundation slab. It is critical that the formwork is sturdy and well-built, as it directly influences the quality and the structural integrity of the finished foundation.

Reinforcement

To enhance the durability and strength of the concrete slab, reinforcement materials such as steel rebar or wire mesh are used. These materials are laid within the formwork before the concrete is poured. They help to distribute the loads and stresses across the slab, preventing cracking and structural failures. Reinforcement is particularly important in areas prone to earthquakes or other types of ground movement.

Pouring and Levelling Concrete

With the formwork and reinforcement in place, the next step is pouring the concrete. Concrete trucks deliver the mixture, which is then poured into the formwork. Skilled workers use tools like screeds and floats to spread the concrete evenly across the formwork and level it off. This step is vital to ensure that the surface of the slab is smooth and uniform, as any imperfections could affect the stability of the walls and structure built on top of it.

Curing Process

After the concrete has been poured and levelled, it needs to cure. Curing is the process by which concrete hardens and gains strength. This stage is critical and requires keeping the concrete moist and protected from extreme temperatures for several days. The curing process helps the concrete reach its maximum strength and durability. It is often overlooked but is essential for the longevity of the foundation.