Always check underground before starting work

Another day in the office. Always check underground before starting work.

Recently we were assessing some existing foundations, before starting building work, with a Sheffield City Council Building Control Surveyor. The project involves building a first floor extension on top of an old single storey extension.

We also had a look at the drains as well. Turns out they are about 1.8 metres deep underground and fairly big ones, about 225mm diameter, so serving a lot of houses further up the drain run.

Turns out the old extension was possibly built illegally, with the foundations too shallow and bearing down on top of the drains. This is risky as the weight of the extension may crush the drains, causing failure and backing up of the foul drains further up-stream, which could be really messy and disruptive. There is legislation in place to ensure this sort of thing doesn’t happen.

As a result, we now have to consider special piled foundations to reinforce the old extension and to take down the weight of the old extension and new extension on top so the loads are distributed down below the level of the drains.

We are also consulting with the local water authority to see if the project is feasible and if they will allow it. This is before any designs are prepared. If it turns out the water authority don’t give permission then we won’t bother preparing the designs, thus saving the clients money. So, just make sure you always check underground before starting work.