Back-filling House Foundations

[Paul200]

Hi all

I've recently had to chisel my way under the wall of our house to install a mains water pipe (we had a private water supply previously). The foundations are actually a minimal 150mm approx. of concrete on top of the solid rock that is present very close to the surface here on the SW coast of Scotland - I hesitate to say 'Shale' in case I get fracked :?

Now the pipe is installed I'm wondering how to go about re-instatement. Should I replace the stone I removed from below the wall with concrete, or will back-filling with the spoil from the trench be sufficient? I haven't disturbed the existing 'foundation' because the pipe had to be as deep as I could get it - there is still some rock spanning the hole as well as the concrete.

My thoughts were to make a masonry culvert around the pipe and continue building up to the rock/foundation above. Then back-filling around this with the trench spoil. Any thoughts please?

Cheers

Paul

 

[Woody2Shoes]

Hi - if it were me - and assuming your foundations are still unaffected - I'd put a few shovel-fulls of pea shingle or fine grit around the pipe itself (normal way to protect it from sharp-edged stones) and then just back-fill with the same material you took out of the hole - job done!

A bit like this idea: http://www.draindomain.com/pipe%20beddi ... ation.html

I also just found this: http://www.waterplc.com/userfiles/file/ ... y_pipe.pdf

Cheers, W2S

 

[Paul200]

Thanks for that Woody. I've actually seen the water company fact sheet in my research. My real concern is not so much the water pipe but the fact that my house foundation is the rock that it sits on - part of which I have removed. Normally the pipe would go under a concrete foundation slab or, with deep foundations, through a ducted hole drilled in the wall. My operation was a whole lot more brutal than that and I don't know the accepted method to reinstate it. To be honest, the whole house is a steep learning curve. Bits of it are 180 years old, stone built straight onto the rock with not a hint of damp anywhere. Other bits are about 30 years old with sweating concrete floors. They really don't make 'em like they used to!

 

[blackrodd]

If I recall correctly, Here in Sunny Devon, concrete footings and mains services are recommended at a depth of 500mm, for frost protection so for you're own benefit, I would enquire what you're local Building Control recommend to help prevent freezing water pipes etc.
You ought to sleeve the pipe where it passes through the building to allow movement in the various temperature changes we can experience.
Concrete or solid fill ( masonry etc) around the sleeved area.
Regards Rodders

 

[Paul200]

Hi Rodders

750mm up here for water - but with an allowance for common sense. I was glad about that bit when the trench contractors hit the rock. I managed to keep the bottom of the trench at 500mm under the wall and that was acceptable to Scottish Water. The pipe is well insulated and sleeved.

Thanks for your confirmation - better get the mixer out.....

Cheers

Paul