First Steps in House Construction
The foundations are the first major feature in house building, but before this, a survey is normally carried out to check the ground and the surround of the proposed foundation site.
A professional ground survey is carried out by a structural engineer, who will probably have trial holes dug around the site to get an idea of the best means of placing the foundations.
By hiring a structural engineer, you will probably have to accept that most will opt for the most robust answers to foundations, having been given the onus of responsibility for finding problem free solutions.
It is of course possible to self-assess the construction site in the knowledge of what an engineer would normally look out for, such as proximity to trees and root systems, soil types, is it clay, marshy, etc. which are often recognisable without trial digs.
The local building inspector, who will have to be used once the build begins, should have experience of the area, local builders and householders near the site should be able to help build up a picture of whether a specialist engineer is needed or not.
Pricing the foundations can be an inconclusive affair until the ground is opened up, it may then be straightforward, but may also reveal expensive obstacles to deal with such as old foundations, or wells, pits, or undocumented drainage channels.
The depth of the foundation will be indicated by the building inspector, and the width by the method of the base. If a minimum layer of concrete is laid, 250mm, with the intent of building up with blocks, there will have to be room for brickies to work.
The usual and more economical is strip foundation, in which concrete is poured in to the required height, which is usually to within two brick courses of finished ground level.
Construction foundation sizes are determined by the loads to be placed on them. The load is spread across the property, focusing it on the walls which are built on top of the foundation.
The roof, for instance is a very heavy component within the structure, and that weight is transmitted via roof trusses to the walls of the building. Similarly the suspended floors weight is spread to supporting walls.
The whole of the “loading” is calculated for the property and the foundations constructed in accordance.
There comes a limit to the depth that trenches can be dug and concrete filled, at around 2.5metres, so piling is the normal after this.
Piling drives tubes downwards until they reach a stable course, and the “tube” filled with concrete, and the whole foundation gets topped with a ground beam to build off.