Foundations for long retaining wall

[Ramsey]

Hi,

Please can I get some advice on a long retaining wall that I need to build.

Basically, the wall will be a semi-circular retaining wall, going from about 0.5 metre either end, with the middle being about 2 metres high. The wall will be built with concrete blocks laid flat, with a stone wall facing. That means the thickness of the wall would be the width of the block (215mm) plus the thickness of the stone wall in front (300mm).

I plan to dig the foundations myself, then get a company to lay the concrete, and a brickie to build the wall. But, how deep and wide will the foundations have to be? Also, because the wall will be about 35 metres long, will it need to have expansion joints in it, and will the foundations need expansion joints of any kind or will just poured concrete all in one go be ok?

Many thanks,

Ramsey

[lutonlagerlout]

i have done curved walls but maybe only 20 m long
you need to find the centre of the arc and measure from that
footing needs to be at least 700mm wide to give you 100mm tolerance
i have never put expansion joints in footings but if the ground is clay you may need clayboard expense
IMHO it will be better if the brickie builds both the blocks and the stone simultaneously otherwise you could get problems
i know you should have expansion joints every 9 m or so but it will look kak on the stone work
can you not step the wall thats a very flat arch rising only 1.5m over 35 m?
cheers LLL



Edited By lutonlagerlout on 1192901444

[Ramsey]

Thanks LLL,

How deep do you think the foundations will need to be?

I don't reckon I'll use clayboard, as it is only a garden wall and not a building foundation.

I don't understand what you mean about:

can you not step the wall thats a very flat arch rising only 1.5m over 35 m?

Thanks,
Ramsey

[lutonlagerlout]

do you mean curved from a plan view i.e. above or curved from an elevation view?
i would hazard a guess at 450mm deep with 300 of concrete,
and rams its a bit more than a normal garden wall really,are there any trees nearby etc etc
if you hit chalk you are fine
cheers
LLL

[Tony McC]

Foundation should be 200mm wider than wall width to allow for 100mm of spread either side, and not less than 150mm deep. If you have a weak sub-grade, you might need steel re-bar and/or additional concrete depth.

It's not usual to incorporate expansion joints in concrete foundations but it can be done if they're considered necessary by an engineer (which you should be using a sthis wall is more than 1200mm high).

Vertical exp joints are now incorporated in stone walls just as they would be with bwk. I thought it was a max of 10m centres, but LLL could be right with his 9m figure: he does more walling than I. At 35m long, I'd suggest 3 exp jts at 8.75m c/c but check with your engineer.

[lutonlagerlout]

i am only going by recent drawings of BWK i have seen ,but i do feel expansion joints ruin the look of face stonework
without seeing the site its impossible to say 100%
cheers LLL