foundations depth....

[b21playa]

Hi all

Does anyone know the rough depth of foundations for a 1930's house?

Well actually its an outbuilding (WC and store) about 1m from the house. Was built with the house.

I was planning on extending this (subject to permission) and needed to know what depth I had to dig for footings to be able to price up the work.

Does the depth need to be the same?

Thanks in advance
B21

 

[Static]

Chances are the existing 1930's WC has a few brick corbels are next to no foundation below. Probably about a spades depth down.

If you are looking to put a perminant structure up then you should be doing proper foundations for the part as well as potentially improving the old. 1m deep footings are pretty much the norm (unless your near trees and in clay or on a river bank or anything else unusual).

Kinda depends what you are looking to do with your WC.. will the shed/wc become part of the main house? or will it still be independant? are you converting it into habitable space?

 

[schiz]

Having been in similar position (1930s house, lean-to beside) a spade depth may be optimistic . As Static says, 1metre is standard, but your building control officer has the final say on this, so no point pricing up the job until you've spoken to him/her.

 

[b21playa]

Thanks all for the reply

Ive just dug down a bit (3bricks down) and can still see bricks below

I want to just make the WC bigger to accomodate a sink and shower cubicle. The rest of the area will be used as a laundry room.

 

[freddiemercurystwin]

If single storey, you'll likely be able to retain any existing walls you want to keep by insulating on the inside and do the new in traditional cavity. As long the wall is sound and as long as you're doing a simple flat roof above if its stood up since the 30's it ain't going anywhere now. It would be hard for BC to insist you rebuild it because of this. As mentioned 1m is the norm, the inspector for your area will be familiar with the strata and will be able to give you a good idea as to what you can expect when you come to do the founds. Phone Building Control and ask to speak to the inspector for your area, they're usually happy to offer simple advice like this. Realistically when he inspects the foundation trenches he'll probably stick his thumb in the ground to see if its firm or not. He may possibly want to see a trial hole dug to expose the existing wall base.

 

[b21playa]

indeed it is a single storey, only 2m x 1.8m in total with a pitched roof. Was going to construct it in solid 140mm concrete blocked, laid flat (as I have about 250 left over), external render and internal insulation

 

[Deluks]

Why laid flat? lay them normally, 140mm wall thickness will be much more than adequate.

 

[b21playa]

Why laid flat? lay them normally, 140mm wall thickness will be much more than adequate.

because the old wall are double brick and these will line up better, so I wont have steps in the brickwork.

 

[Deluks]

Why laid flat? lay them normally, 140mm wall thickness will be much more than adequate.

because the old wall are double brick and these will line up better, so I wont have steps in the brickwork.

Don't quite follow, You will be rendering outside so joints won't be seen. If you want a flush wall internally then just make up the space with extra insulation, bonus.

 

[b21playa]

Why laid flat? lay them normally, 140mm wall thickness will be much more than adequate.

because the old wall are double brick and these will line up better, so I wont have steps in the brickwork.

Don't quite follow, You will be rendering outside so joints won't be seen. If you want a flush wall internally then just make up the space with extra insulation, bonus.

Wouldnt it be better for me to have block laid flat and then insulate all the walls (old and new)?

I have enough blocks spare in the garden and want to use them up to be honest, as its a mess in the garden

 

[Deluks]

Could do. Could also freecycle or ebay the blocks. Also, with extra space for insulation you will be able to use a thicker but much cheaper form of insulation and still get the same performance.
Polystyrene or rockwool slabs for example.

 

[b21playa]

Just dug down the side on the wall to expose footings

7 bricks down (600mm) and it seems the last brick is sitting on a clay tile. Didnt have time to dig any further as it started to rain

does this seem about right?

Also how wide will footing have to be and at what depth?

 

[b21playa]

could the existing building just the laid directly on the soil?

I can see concrete, but a sort of clay tile under the bricks.

Tomorrow I will demolish the back wall and dig down to double check

 

[noseall]

could the existing building just the laid directly on the soil?

Older buildings' (footings) were laid directly onto soil.

 

[b21playa]

could the existing building just the laid directly on the soil?

Older buildings' (footings) were laid directly onto soil.

Hi

Thanks for reply.

So if I was to extend the building slightly, how would I match the foundations up?

Should I ensure the top of my new foundations is the same as the bottom of the new or the bottom of the new is the same as the bottom of the old?