Wall width/foundations on extension

[GoldBoo]

Looking for some advice please, we’re looking at having a small rear porch built (just somewhere to house the tumble dryer, hang a few coats and pairs of shoes). But I’m trying to find out (1) what is the depth of the average wall and (2) how far beyond where the walls will be do the foundations need to be dug out? Just so I can work out what we'll actually end up with in terms of internal space. Thanks

Bump

We are going out 3m walls are brick and block, and are 30cm thick. Foundations are huge but we are going up a second story so don't know if that means they are bigger.

Yes, 30cm for your average external wall (internal walls are thinner). Can't help on the foundations, ours was double storey too.

Foundations are now usually required to go down 1 metre don't hit rock, in which case they just keep digging.

Ours went down 2.4 metres! Took a lot of concrete to fill them

Depends on your ground conditions. A basic strip foundation on solid ground would extend 75mm either side of your wall. However, you can get a structural engineer to design them flush with your wall.
A traditional modern wall would have 100mm brick with a 100mm cavity with 100mm blockwork construction plus 3mm plaster etc.
Have a consultation with a designer/ architect though.

Interesting, thanks everyone. So to get an idea of where the internal space would start, I just need to measure in roughly 400mm..

If we were to have a half brick wall conservatory, are those low walls any thinner?

What are you trying to do and what's the space? Very small extensions can be quite expensive per square m.

We have a space of 2x3 metres (before it would start to eat into areas of the garden that I like and don’t particularly want to build on), I would like a small rear porch type area just to house a tumble dryer and the kids coats/wellies when they come in and out from the garden. At the moment all the mud gets dragged straight into the house and I would like to be able to shut off a mucky area. Perhaps it’s too small.

I wouldn’t want to fit any fancy shoe storage in either. Just a trug for wellies and a few wall mounted hooks. Having them come into the house straight onto my lovely clean carpet is driving me a little insane at the moment