It may be a tired cliche that every home needs to be built on a solid foundation, but it is no less true for that, and choosing the right style of foundations for your new home is vital to its long-term strength, stability and safety. However, choosing the right foundation type for your home is not as easy as it once was, and a variety of more modern foundation types are taking the place of traditional raft, pile and pier foundations. One of the most popular of these innovative new foundation types is commonly referred to as waffle slab foundations.
What are waffle slab foundations, and how are they constructed?
To the untrained eye, a completed waffle slab foundation looks very similar to a conventional raft foundation made of ordinary, poured concrete slabs. However, waffle foundations differ in a number of ways.
Conventional raft foundations are formed by excavating a void for the foundation, before digging a further set of parallel trenches into this excavation and reinforcing the earth between them. If you could look at the underside of a foundation constructed in this way, it would appear to have a number of parallel 'ribs'; these ribs provide strength, stability and resistance to foundation damage, and have been an integral part of all raft foundations for a number of years.
Waffle slab foundations are essential an extension of this basic concept. Instead of digging trenches in the space excavated for the main body of the slab, a number of square void formers (essentially reinforced plastic boxes) are arranged in the excavated area, before being covered with poured concrete. This creates a distinctive 'waffle' pattern on the underside of the foundation, which outperforms the traditional parallel 'rib' arrangement in a number of areas.
What are the advantages of choosing waffle slab foundations for my new home?
Good for expansive soils
One of the main reasons waffle slab foundations became so popular so quickly is that they perform exceptionally on ground laded with expansive soils. These clay-rich, highly absorbent soils can massively increase in volume when exposed to water, and the shifting, heaving movements created by this absorption can cause severe cracking, crumbling and subsidence of more conventional slab foundations.
Waffle slab foundations are far more resistant to these movements, largely because the reinforcing 'ribs' of the foundation extend in found directions rather than two. This reinforces the foundation against the irregular shifting movements caused by expansive soils, and also helps root the foundation more firmly in place to prevent damage caused by foundation movement.
Little ground penetration required
Because waffle slabs do not require as much excavation to build, they are very useful for constructing homes in areas with pre-existing subterranean structures, such as water pipes and gas lines. This makes them especially popular for use in urban and suburban areas.
Unlike convetional raft slab foundations, waffle foundations do not require excavation of extensive trenches, and the void formers used to create the distinctive waffling, while not reusable, are cheap and easily replaced. Consequently, waffle slabs tends to be considerably cheaper and faster to construct, cutting down on labour costs and allowing your home build to run to a tighter schedule.