How thick is an external wall?

melt71

Strange question I know, but I am in the early stages of planning a 2 storey extension and need to know how thick the external walls will be so that we know how big the actual rooms will be inside - the extension will be at the side of our house on our driveway which is just over 2.5m wide. We will be building right up to the boundary.

We know the rooms will be long and thin but we just want to make sure that it is workable. ie will we be able to get a bed and wardrobes in there comfortably!

At least 3 neighbours have put similar sized extensions on their driveways but all of the drives are slightly different sizes so I can't get any info I need from their plans.

We plan to project manage this ourselves as my OH used to be in the building trade and his friends will be doing most of the work needed, so if anyone has any advice or links about doing an extension of this size I would be very grateful

Many thanks

hewhoisnotintheknow

open your front or back door and measure it

andrew-b

Depends on the type of construction used...
brick outer leaf/ block inner leaf,
timber frame
block inner/outer plus render and so on.

Andy

andrew-b

See here:
http://forums.moneysavingexpert.com/showthread.html?t=981697


Andy

bryanb

Remember, you will need the cooperation of the landowner next door if you intend to build up to the boundary. Remember the width of foundations, the neighbour will probably not want them on his land.

melt71

hewhoisnotintheknow wrote: »

open your front or back door and measure it

Thanks for that :rolleyes:

If you read the question I am asking about new builds not my existing walls! I wanted to know if there was a standard width required for building regs.

Thanks for taking the time to reply though.

melt71

bryanb wrote: »

Remember, you will need the cooperation of the landowner next door if you intend to build up to the boundary. Remember the width of foundations, the neighbour will probably not want them on his land.

I should reword that a little, we are intending to go right up to the limit but not onto his land!

We've already had planning permission granted for a single storey extension many years ago but we never built it, as it went up to the boundary but obviously didn't go onto his land. This will be a completely different extension and will be at the same levels as the existing house front and back whereas the other was 1/2 way down the drive but went right out into the back garden.

Thank you Andrew-B. Our existing build is block & brick.

macka0

knock of 300 mm for both skins and cavity

planning_officer

Have you actually sought advice from the LPA about your proposed extension? Rarely will you be allowed to go right up to the boundary at first floor level.

Thomas_Crown

macka0 wrote: »

knock of 300 mm for both skins and cavity

As soon as I saw the question I thought 11 inches as that was the thickness of a standard wall at one time.( 4'' wall - 3'' cavity - 4'' wall). 300mm is 11.75 inches in real money.:D

McAzrael

Thomas_Crown wrote: »

As soon as I saw the question I thought 11 inches as that was the thickness of a standard wall at one time.( 4'' wall - 3'' cavity - 4'' wall). 300mm is 11.75 inches in real money.:D

3" cavities are quite rare now because they struggle to take enough insulation. 100mm brick/block - 100mm cavity - 100mm block - 15mm plaster is quite typical, so 315mm all told. As someone has pointed out up there, you will also have to allow at least another 150mm for the footings (unless you have a particularly generous neighbour), more if your neighbour does not want your guttering over his land.