Tips & Tricks

Excavate and Build Under Question

A video Tutorial

This video was made in relation to a question we received about stopping water running under a house – but the concepts for excavating and building under an existing house are similar.

Note that to increase your space under a house, you can remove posts but steel or timber beams are needed to support the floor loads. You’ll need a structural engineer to help with this work.

Excavate and Build Under a brick House

The conventional way of excavating and building under a house is to stay clear of the brickwork walls and building new retaining walls and slabs to suit the required head height.

Retaining wall under an existing house for a build in under project

Staying away from the existing external footings is a good idea as brickwork is liable to crack if the ground subsides or shifts when excavating. The new retaining walls only need to be low walls and the strength of the retaining wall can be built into the new slab.

Undermining a house footing to create more space

Don’t forget to consider drainage when building your retaining wall because you might find that water running downhill through the ground suddenly starts seeping through your retaining wall.

The best way to attack these drainage issues is by collecting water and diverting it away from your house before it gets anywhere near the walls. Spoon drains are better than pipes because they are self cleaning and easy to maintain whereas pipes tend to get cloged with leaf litter.

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