Hi all,
From searching around it seems that I should expect to pay £700 to £1500 per m2 for an extension (this is near Aylesbury, so probably over £1,000 I’m guessing).

I am planning to raise a single story double garage to two stories. I would salvage the current tiles myself, which should (baring many breakages) be sufficient for the new roof. I’m not sure that the pitch of the roof is the same as the main house, so assume the ‘A’ frames will not be reusable (unless I’m very lucky).

It would be great if anyone could help with the following:

– How often is it possible simply to build on top of the exisiting walls (I accept that an inner skin of blocks and insulation may be needed as it is currently just a garage)?
– If this is not possible due to foundations not being suitable, how much will it cost to get the old ones out and new suitable ones in?
– How much could I knock off the cost by salvaging and reusing the roof tiles myself?

Many thanks for any help

  • Mark Brinkley

    Good questions, Kev. Wish there was a straightforward answer. The chances are that there isn’t a great deal of value in the salvaged materials and there will be a lot of hassle in using the existing garage structure, especially if you want to use it as living space in future. It may well be simpler (and therefore cheaper) to demolish the existing structure and start again. The state of the foundations is almost unknowable without demolition and it’ll take a brave engineer to say that what exists is adequate for an extra storey above, so you may well have to replace the foundations in any event, in which case demolition may be the only sensible option. The only question is the salvage value of the existing materials which can only realistically be done by valuing what’e there on site and comparing it with the cost of replacements.

  • Stephen Margerison

    Hi Kev, the answer is probably YES ! you can build on the existing structure. so first, dig down next to the garage in say 2-3 places, and expose the foundations (on both sides) unless one side of the garage is attached to the house. Then you can leave that side, Then ask your building inspector to come take a look. Only he can tell you ! I would suggest a timber frame be fitted, as its easier and a lot less weight. The timber frame would be mechanically bolted to the existing gable wall. then across to the new inner wall you have to build. then up you go. If you need further details, e mail me as I have just done the exact same thing.
    regards, SKM

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