House foundations aren’t generally considered one of the most exciting aspects of the home renovation or building process, however they are vital to the overall structural integrity of your home. Until the 1970’s, Melbourne homes were traditionally built on timber or concrete stumps with timber bearers. As construction processes and techniques have advanced in recent times, foundations have also evolved with concrete slabs becoming the new normal. With over 30 years’ experience completing home renovations and extensions throughout Melbourne, Duncan Thompson Extensions is a trusted home renovation builder who understands the different foundation types available and can guide you on the most suitable choice for the new addition to your home. Read on to learn more about each foundation type and a few factors that may determine which one is the better solution for you.

Building on Stumps

This involves a sub-floor of horizontal bearers (beams) that support joists (a smaller, closer spaced beam on which the flooring material rests). The bearers sit on stumps which are adjusted in length to all be level with each other.

Building on a Concrete Slab

Slabs are simply large solid expanses of poured concrete that contain reinforcing materials such as steel mesh and reinforcing rods The slab can be a sub-floor and floor structure, with other flooring finishes laid on top, or it can be sub-floor, floor structure and floor finish if it is polished and finished with a lacquer. Depending on the site and soil requirements, there are a number of different slab designs available. 

Things to Consider

There are pros and cons around which method is better, but it can depend on a few factors such as:

  • The site, especially the soil type and the topography
  • The style of the home
  • The preferences of the homeowner
  • The cost to construct

There are also a few other things to take into consideration when selecting a foundation type, these include:


Generally speaking, homes built on a concrete slab achieve higher energy ratings due to excellent insulation provided by the concrete. Homes built on stumps may require careful attention to insulation of the subfloor in order to achieve an acceptable energy rating.


Concrete slabs can significantly reduce the transfer of noise from one level of a house to another, and between rooms on the same level. While most airborne noises aren’t transmitted through a slab, impact noises might be. An acoustic barrier can be included in the ceiling to reduce such noise.


Concrete slab foundation usually costs less than stump foundations, this is mainly due to the fact that construction of the stumps and sub floor framing is more labour intensive. They also require more insulation and the extra height stumps require may mean more cladding materials around the exterior of the home.


Concrete slab foundations are usually considered to be more solid and less susceptible to movement within the building. If done correctly, a concrete slab foundation should have an infinite lifespan.

Block Type

Usually concrete slabs are used for flat building sites, although they can be used on a sloping site, but this will often cost a lot more. Stumps are commonly still used for homes and extensions on sloping sites, where the floor level is raised above natural ground level whether this is to capitalise on views or to adhere to a minimum flood level requirement.

Which Foundation is Best for My Extension?

Renovations and extensions can often incorporate concrete slabs even when the original building does not. Extensions can use slab-on-ground or suspended slabs and when renovating rooms with timber floors, it may be possible to replace the timber with a concrete slab for added insulation. Each site is different and each home is different, but remember that no matter which foundation type used in your home renovation, the outcome will be the same – the result will be a solid home built to stringent Australian standards.

At Duncan Thompson Extensions, we look at each site individually and can advise on the best foundation solution for the project. If you want an experienced Melbourne home renovation builder who is passionate about quality workmanship and design, contact us today on (03) 9836 8655 or enquire online now.