Can I build on top of a garage?

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Our house was built in 1968 and has a link attached garage that is not quite a double, but perhaps 1.5x the width of a single. The concrete floor in it is badly cracked and rather damp.

I am thinking that it may be possible to extend the garage width wise and also build another storey on top. I guess it will be down to what foundations exist as to what is possible, but they are buried under the concrete.

What type of trade can determine if it is possible to build on top, or whether the whole lot should be demolished and start from scratch? With builders, surveyors, building inspectors and architects all potentially part of the equation - who do I start with?

with thanks

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Problem with that is that it will destroy the tarmac drive that goes up to the garage. I expect someone will have to dig out some concrete inside. But who is qualified to assess - 'yes, it will be OK to build on top'?

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Question is....are builders always right? Are they 'qualified' to make that judgement? It would be a nightmare if they say 'yes, you are OK', then get plans drawn up, planning permission granted, then it all goes wrong and have to start from scratch when I may as well have done that in the first place.

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Ah - OK. If it that is the way, I can dig down myself and find a structural engineer in. Again, do they need to see just one point or a point under each wall?

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elanfan said:

There was a thread here not long ago where a neighbour wanted to infill a link in a terrace. Basically had his arse handed to him.

Not sure what that means, but when I said 'link attached' I meant that the garage is kind of connected to the house, but only by a shared flat roof that goes over a passage and becomes the garage roof. We do not have a neighbour.

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Here is back view. The walls are double. Red brick inside Marshallite outside.

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And the front

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And how it joins the house...

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Thanks everyone. Sounds like I need a structural engineer after I have got enough floor up to see the foundations. That will provide enough information to make a decision.

Many thanks.

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Thanks. House was built 1968. I did Not sure whether the Council will be able to supply us with plans. If they exist Ivsuspect they will be in an archive.

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Electronicpants said:

Rip the roof off and put in 4 steel columns around the perimeter of the garage walls on pad founds internally (like an oil rig/mezzanine floor), steel perimeter frame connecting the 4 columns above to form your new second floor and garage "roof" and lay the joists into the steel, then you are separating any element of the original build with new, your new second floor would be a light weight design timber kit with a lathed render finish, however it may be cheaper to knock it down and start again!

Edited by Electronicpants on Thursday 17th June 11:33

Thanks - sounds like a plausible idea!