Building Foundations

Getting Down to the Foundations

Building new houses, or even building extensions onto existing houses, will mean that whatever the type of build that will go up, it is going to need footings and foundations.

Foundations will not be seen once the build is complete, but that doesn’t take away the importance of getting them established correctly.

The foundations by their very name, are what the house will be built on, and will be responsible for bearing the load of everything from the roof down to the damp course.

Architects plans must be adhered to, but often, until the ground is broken into, it is not clear what depth the trenches are going to have to be.

The plans will certainly lay out where they are going to be, and accurately marking out with survey line first, can bring the plans into perspective.

The trenches will signify load bearing walls, and the minimum depth for all of these is 1 metre, but each site is different, and the local building inspector will make the judgement on the necessary depth at this point.

The criterion is the nature of the soil itself. The sides of the trench are as important as the floor of it in supporting the load, and firm load bearing soil such as clay or chalk would be fine for the minimum depth trench.

To find stable solid ground, the digging can go down as far as 2.5 metres, after which it becomes uneconomical and unsafe to go down further and calls for engineered foundations.

In general conditions, trench fill foundations can be used, with ready-made concrete poured into the trench, to within 150mm of the surface. These are normally dug using backhoe loaders or similar construction equipment ideal for the purpose. Backhoes are one of the most versatile pieces of equipment found on many construction sites due to their flexibility for many different tasks. Find the best backhoe loaders at Hanlon CASE, suppliers and maintenance for leading construction equipment.

Should the build be in softer soil, strip foundations can be used to spread the load of the building out over a greater area. This will entail a concrete base of around 250mm at the bottom of the dig, and then building up with blockwork to ground level.

Should neither of these two types of foundation be suitable because unstable ground is too difficult to achieve then engineered foundations will be required. The most common of these are pile foundations.

Piles are driven into the ground by a pile-driver, and the tube filled with concrete to become a pillar. The whole foundation is topped off with a ground beam to build off.

At this stage of digging foundations it is as well to dig the drainage trenches. Provided they are deep enough it is prudent to lay the cabling for services, such as water, gas and electricity to save disruption prior to first fixing.