Is a concrete slab the right foundation for my ecokit home?

Foundations are one of the most important elements of a house. It is crucial to get them right as they will have to last years to come and take a lot of abuse from the elements – water, heat, frosts…

In the case of improperly poured foundations, it doesn’t take much for the foundation to lose its integrity. Here are some tips on what to watch for when planning and pouring a concrete slab.

The choice of a most suitable foundation type for your site is the first step in making sure it lasts forever. Start by getting a geotechnical report (commonly known as ‘soil test’) to find out what category your soil is. It is crucial to choose the right type of foundation suitable to your soil – getting this wrong can cost you a lot of money and a lot of headaches!

Concrete slab generally means a slab-on-ground. This type of construction is particularly popular in housing construction around Australia. A slab on ground for an ecokit home can be one of a number of different types of slab such as a raft slab, waffle pod slab, slab with dropped edge beams or a reinforced slab on fill.

Attention must be given to a potential ground movement and keeping out the damp and the cold. Another important component of a slab footing is the termite protection.

Concrete slab floors with direct thermal contact to the ground can present challenges to the maintenance of personal comfort in homes and add to heating bills. A solution to breaking that direct thermal contact is to use insulative material.

Benefits from the installation of such a system can accrue in both summer and winter. During winter, heat loss through the floor of a building can be decreased, while in summer, differences between floor and air temperatures are minimized and condensation on cool floors is avoided- providing a more comfortable and energy-efficient environment.

If you are building a high-performance, energy efficient home and you live in a climate where you either heat or cool your home most of the year, we strongly recommend insulating your slab. At ecokit, all our projects are modelled in PHPP (Passive House Planning Package) to calculate accurately the heating and cooling demand and to determine if the slab insulation is needed or not. In most cases it will be, no matter what your builder says.

A natural insulation for a concrete slab

If your slab requires insulation, polystyrene will be most likely the material specified by your engineer or builder. Don’t get me wrong, polystyrene is perfect for this job – it’s lightweight, easy to work with, it’s a great insulator and it’s also cheap. Unfortunately, polystyrene also causes very bad environmental pollution.

Before the construction of our prototype home in Jindabyne, I searched high and low for a natural material that could be used instead of foam materials. I have been recommended hempcrete however I couldn’t find any confirmation it can be used for a structural floor.

Then, I stumbled upon AUSPERL Perlite, marketed as easy-to-install, light-weight bags that may be used as insulation below concrete floors as demonstrated in the accompanying photographs and schematic diagrams.

Perlite under-slab insulation is a natural, inorganic product that does not rot nor provide habitat for rodents. Because of its neutral pH, the product does not foster corrosion in piping and electrical wiring that may be in the underfloor area. In addition, perlite is dimensionally stable under varying temperatures and it is not combustible.

Avoid excessive moisture

Plumbing leaks can wreak havoc on your foundation. to avoid any major incidents. It is usually recommended to have the plumbing inspected every few years.  Catching a leak early will not only save your foundations, but it will also help you save thousands on your water bill. Avoiding moisture in the concrete or around the house also helps prevent mould build-up that can eventually spread inside your walls and into your home.

You should keep an eye on all of the cracks you notice around the house, including their length and width. Check the cracks for growth on an annual basis and call a contractor if you think there may be an issue.

Large trees in close proximity to the building

Large trees close to your planned home can also be detrimental to your foundation as the roots can dig their way into the foundation and cause serious damage. Roots can also erode the soil and create a drainage problem. As a rule of thumb, if the branches can reach the house then the roots can as well. If your house already has trees that are too close to your chosen building site, then consider having them relocated to a different part of the property if that’s possible or installing a root barrier around the foundation to prevent any issues.

Concrete slab is a common type of foundations and if designed and done properly, they are totally suitable for an ecokit home. Although foundations are not included in the Essentials package, we can still help you to select the right type of foundations or organise the engineering of the slab for your ecokit home. Just sent us your site survey and geotechnical report (soil test) and let’s have a chat!