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Foundation for second storey extension


I bought my end of terrace house 3.5 years ago which already has a 3.5 x 3.8 metre extension to the rear of the property. According to the documents I have, originally this was a conservatory built in 1983 and then converted to an extension in 1987. I have the planning permission approval documents but no plans.

We now want to build a second storey extension over the top of this extension (currently a flat felt roof). How would I know if the foundations are deep enough? And if they're not, is there something I can do to enable me to build on top of this? If there is a method for checking the depth of the foundations, is it something I can do (basic DIYer) or would I need some sort of certificate to verify it?

Thanks in advance.


2 Answers from MyBuilder Extension Builders

Yes you need to dig a pilot hole next to the footing..... I doubt very much that you have the correct depth of footings which will need to be minimum 1m.

The existing structure can be underpinned to make it strong enough to take a second storey but this will not be cheap....... If you find that the footings are not deep enough I would consider a loft conversion instead ;)


Answered 4th Jan 2015

A couple of pilot holes would need to be dug in order to determine the depth of your existing footings , a call to your local building control can put your mind at ease they will likely send out a BC Inspector to advise you on any actions you are looking to undertake.
Many Thanks Dan


Answered 4th Feb 2019

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