What is a Raft Slab?

A building’s foundation serves to make sure that it is stable and that it stands firm for a long time. From an engineering standpoint, a foundation functions to distribute a structure’s load (or weight) over a large area so that the soil directly beneath it does not get overloaded. For construction purposes, a foundation provides a surface that is level to build on properly.

A raft slab is a concrete slab that contains slab thickening in areas to create beams that give more strength and assists with distributing the load in an even fashion. It is a common type of foundation for building new properties in Australia.

Raft SlabRaft slabs are designed to spread the load of the building over a bigger area, making them ideal for constructing on soil that is relatively loose. A raft slab is also used when there is a possibility for movement at lower levels of soil, such as land that has already been mined. 

The type of foundation used will depend on the conditions of your soil. Being informed about what kind of foundation will be used for you is important, but it is definitely mandatory to consult an engineer for these kinds of decisions.

Is Raft Slab Better Than Waffle Slab?

Raft slabs are wider than waffle slabs and, therefore, offer more surface area for the adhesive to bond with. But to help you decide which one is better for your home or building project you might want to consider its pros and cons.

Raft Slab Advantages

  • It generally requires a much lesser amount of concrete than a waffle pod slab, saving you more labor as a result.
  • Builders have more experience working with this kind of slab.
  • It is more suitable for sloping lots, as well as high wind areas.
  • It allows moisture through while still maintaining its high-quality look, unlike wood boards which will warp after sitting wet too long due to expansion/contraction caused by temperature.
  • Flexible inside different environments.
  • A traditional slab is much prone to damage or cracks in comparison to a raft slab.
  • They have already been designed to work with large-scale buildings.
  • Can be installed almost at any given lot characteristics due to their floating properties.

Raft Slab Disadvantages

  • Careful attention to the drainage system is a must.
  • Low energy rating.
  • The biggest problem with the raft slab is that it is expensive.
  • More costly than the waffle slab.
  • One common issue when building raft slabs is cracked in the surface, but some builders don’t realize it can happen, mostly only evident once you start driving over them. Raft Slab is a complex material that must be handled with care. 

Leave a comment