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Groundwork & Foundations

Demolish or underpin

I have recently been granted planning permission to extend my kitchen on the ground floor into a space behind the attached garage, (This will take around a third off the back of the garage to square off the new kitchen) and above, a first floor extension running over both the new kitchen and garage. Its a 1970s detached house near Bolton.
Having got quotes for just the build/plumbing/electrics/plastering etc (No fittings) then a builder and inspectors in place, it seems that the garage foundations are not deep enough to take the extra floor. My builder has recommended that the garage be demolished (it's about 9ft x16ft) and rebuilt.

The cost to do this is virtually the same price as the extension build, so doubling the price. Obviously, I was aware there could be an issue with the foundations but didn't realise how much it would cost.
My architect has suggested that underpinning by pouring concrete under the garage (at least the two thirds of it as the other third is in the new build) might be an option. I am not looking for a 'cheap' job, but trying to get the best out of my budget. My builder won't do it, probably due to time. I am just looking for advice on what might be the best option. Many thanks Paul

5 Answers from MyBuilder Groundworkers

Best Answer

I wood under pin it .it is cheaper than take the old slab out


Answered 12th Jul 2019

Have you considered using steel , I have done this a lot recently dig pits front and back of your garage and then use RSJS to span the area causing no load bearings on the garage at all not expensive and quite straight forward to do


Answered 12th Jul 2019

I would definitely underpin.Its cheaper than pulling down the whole building and it will save time and money on the new build. Any good builder would be able to carry this out.


Answered 11th Jul 2019

Under pin with out a problem


Answered 12th Jul 2019

I would brake the concrete ( 9 feet by 5 feet ) that will may take a day and pour a new concrete slab which would take around 3 cubic meters of concrete.Easier...


Answered 13th Jul 2019

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