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Extensions
How can we build over an existing ground floor extension which has inadequate foundations?
Anonymous user 28 February 2024 - 2.34 PM
We want to buy a house with a ground floor extension of approx 4.7 x 10m which was built in the late 1970s. Our aim is to add more bedrooms. We suspect the foundations aren't strong enough & the vendors won't agree to digging inspection pits. What are our options to extend upwards if the foundations aren't good enough please? And what are the likely costs in a worst case scenario situation?
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6 Answers
Anonymous user
worst case scenario demolish and rebuild ,might be able to underpin existing,underpinning allow 8-10k rebuild allow 70k plus depending on spec/scope of works roof structure ect
Answered18 June 2011
6
Anonymous user
hi lee complete building there a few ways to do this steel work up and over with concrete pads to the right depth or pillars on the inside of the old extension to pick up steelwork.
both ways are not cheap
hope this helps
Answered18 June 2011
4
Anonymous user
I can understand the vendors not letting you dig trial pits, as you havent yet committed to buying the house.
Only option is if you do buy the property, is first dig some trial holes to accertain the depths/thickness of existing foundations, engage an architect and structural engineer, they will then advise if foundations need underpinning.
There are now more modern methods for underpinning foundations.
Your architect and s/e will advise and all needs to go through planning and building regs.
Cant advise on the cost as the scale of works is unknown at present, the foundations might even be ok.
Answered18 June 2011
4
D WILSON
Hi your cheapest & quickest option is to knock it down & start from scratch, underpinning is time consuming & expensive. You might be lucky when you can dig a test pit. Costing will depend on many variables including your type of finish i.e kitchen, bathroom etc.
Answered18 June 2011
3
Rupert Burrows Design Contracts
You either have to underpin the existing, or pull it down and start again. Underpinning can cost you an arm and a leg.
Answered18 June 2011
2
Anonymous user
Ask a structural engineer.
It may be you have either to underpin the existing foundations or another way could be using Universal beams and Stanchion to make a steel frame to support the extension above A structural engineer should be able to help with this and also supply plans and calculations for the building control officer (BCO)
Cost is expensive depending on what would be specified
John
Answered18 June 2011
1