Extension over a single skin garage

14 Feb 2011
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United Kingdom

I am concidering building over our attached garage to make an extra bedroom and en suite bathroom. I was wondering if someone could help.

The garage is off the side of our semi detached house and was added 5 or 6 years after the property was built. It garage is single skin so I presume i will have to dig down to build another wall of masonary as to support the 2nd floor.

My question is, as I want to brick the external of the new extension to keep in fitting with the rest of the street, would i have to build the internal skin of masonary for both floors or could i build the internal to support the 2nd floor and have the new extension above the garage as single skin and just insulate???

I would be very grateful if someone could help out on this matter.

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Are you saying you only want to do the first floor part as single skin?

Either way first thing to do is check your existing foundations/wall will lend themselves to having the additional loading of a floor, new inner skin and first floor walls + roof. If not then you're into an engineers solution or knocking the lot down and restarting. Dig down to expose the foundations and then get building control out to have a look.
Thanks for the reply

I have spoken to my local building controler and from the plans from our garage, it says the footings are 700mm deep single skin so I will need to dig down to build an internal skin of masonary. Would it be feasable to bulid the 2nd story using only a single skin and insulating?

Many thanks
In a majority of jobs we do, a single skin garage would be demolished to make way for a new build extension with new foundations etc.

The reason being that it more cost effective and less hassle. For example, the brick coursing may be out of kilter with the house, out of level, inadequate foundations, no provision for inner skin, etc etc.
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The garage was built in 1995 and with the info from building control with 700mm footings will be adiquite to build a internal skin.

If i was to go down this route is it feasable to build and have a cavity wall for the ground floor and to support a second floor with pitched roof being single skin and insulation?

Thanks for the reply
There may be some stability issues with a two-storey single skin extension

If you don't want to demolish the existing, then you could span some steel beams on new internal piers (or steel columns) with new pad foundations, to form a cavity wall at first floor level

Or possibly with timber beams and form a timber framed cavity wall

Or even a timber frame and clad extension, but this may not fit in with the rest of the house
Here's one I did earlier, steel beams were supported off existing piers in the corners which in turn supported the new inner skins/floors

You'll quite possibly need an engineer BTW.

If you want some Planning and/or Building Regs drawings PM me, I'm in Devon too!:cool:
I'm planning on doing something similar above our garage although our house in only 5 years old, is timber framed and the first floor is not only a single skin walled garage but is also a breakfast area off the kitchen. I have no idea how a builder will approach building the inner skin walls for the garage and the extension above?
Hi Andy, How are you getting on with this? I am also in Devon and am facing the exact same quandary at the moment...

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