Two important factors to consider in relation to foundations are site investigation and specification.
A site investigation helps determine what sort of work will be required to achieve a good solid load bearing sub-soil, prior to foundation works starting. The foundation is the first most important part of any build as this is the base for supporting the structure in future years. It will also have an overall effect on the quality of the build and the thermal efficiency of the house design. When deciding on the foundations required, you also have to make sure all of the specifications and details you use comply with current regulations and are in line with the local building authority’s guidelines as these will impact on the design and type of build system.
Ideally, you should incorporate a local specialist (e.g. Technician, Engineer or ACJ Group) to oversee the designs and build. Arrange for the site to be properly assessed by a structural engineer who can make recommendations on the appropriate foundations required.
There are many different types of foundation designs and procedures incorporating different insulated build ups. These designs and systems are dictated by the type of ground you intend to build on and on your house design. Examples include, traditional brick n block methods, standard timber frame or high insulated closed panel construction. The build type and its relation to the ground works will dictate the best solution for creating a sound foundation.
There are a variety of systems currently being used for foundations including pilings, piers and concrete spread footings. The more traditional build method for brick n block and timber frame construction is a solid poured concrete block creating a footing/slab running the area of the load bearing walls required external and internal. Building blocks can then be used to build the external supporting wall head, up to the required area for holding in the house floor design and creating a starting point for the external walls to be built from. This is key to creating a smooth and successful build. Diligence is required to maintain quality and in the setting out of all dimensions, making sure the wall heads are as level and plumb as possible. The internal foundation build can vary and will have a variety of layers building up to the finished floor level.
A common procedure would be to incorporate compacted hard-core, sand blinding, vapour barrier DPM, solid insulation, reinforced concrete slab, floor battens and flooring. If you are incorporating under floor heating, this build-up will replace the battens and flooring resulting in a poured concrete wet mix spread over to form a finished floor to suit supplier’s recommendations.
If you want to build a high insulated low energy home always check the cost implications of the build-up specified and be wary that designs and details can be over engineered and specified so having a set price for the foundation will be key as this is an area that can absorb a lot of the project’s budget. This will also help to cost out the rest of the build and materials required, allowing you to alter any specifications if needed to help achieve the project build within budget.