Footings Help needed!!

[kld05]

Hi

I'm going to be digging out footings for a single story extension, the problem is where the footings need to go there is a clay drainage pipe running the linear length of the proposed footing at about a 800mm to 1m deep. I can't move the pipe as it goes under next doors extension, so I would not be able to redirect.

Can I concrete over this pipe if it was protected some how? if so how would I protect it?

Any advice would be good!

 

[^woody^]

You need to move the wall if you can't move or divert the drain. Don't forget any required build over agreement from the water authority

 

[Static]

You need to move the wall if you can't move or divert the drain. Don't forget any required build over agreement from the water authority

Ditto this, building the pipe in is not an option..

 

[suggett1976]

Ask building control to come out and get there advise.

 

[theoldun]

Providing you have minimum of 800mm cover above drain and finished ground level, then building on top of a drain is an option, but a very very expensive. option. For a standard 5x3 single storey extension, it will cost as much to come out of the ground as it will from DPC to completion, consequently it is better to either divert drain dependant on fall, or move wall.
If you want to know how to build on top, then say so,
Regards oldun

 

[^woody^]

So

 

[noseall]

So.

 

[joe-90]

So.

 

[landyandy]

So.

 

[tony1851]

It IS possible to build astride a pipe. I did this on my own extension 10 years ago and had no problem.
It is tricky, and expensive, but it involved building two separate foundation strips each side (below invert level) and then bridging over the gap (which was about 18" wide) with a continuous row of 6"x4" p/c conc lintels, and then building the wall on top of that. It needed about 20 lengths of lintel. BC was happy with it; no problems whatsoever so yes - it can be done.

 

[^woody^]

Yes, we've done highly engineered beams and rafts and ground alteration to bridge sewers. The concept is to remove direct loading above and at the side of the pipe, but at what point does the amount of design and expense make it impractical and infeasible?

In addition, the water authorities are very weary in agreeing complex solutions for domestic work which is going to prevent access to their drains and increase risk of damage. The simplest solution of a smaller, bigger or no extension does always seem to be preferable

 

[tony1851]

I wasn't saying it's an ideal solution, just that it is technically possible and, imo,
not out of the realms of DIY.

 

[theoldun]

Nice to know Tony that somebody else also knows their way around under ground on the tube train.
Your way is the easy way and least expensive. We have done an extension and a new build house this way and approval was given both by building control, sewerage undertaker and NHBC for the house. The only additional item we did, was to rattle out existing clay pipe and relay with new PVC-U with accessible entry size IC at each end. Reason so if there ever was any problem with the pipe work a liner or sleeve could be drawn through and blown into place.
The very expensive one that we priced was on very poor ground and had to be piled 4 metre deep with 300mm dia flight auger piles, filled with concrete and RE top to bottom with starter bars above cap
Pairs of piles each side of drain run with 300x300 RE caged ground beam above pairs of piles. Then caged 300x300 ring beam over top of ground beams and piles to remainder of perimeter. The overrsite was RE 150mmm thick tied into cage and the whole flooded and pokered to form raft.
So, yes Tony, you are right there are options, and we agree not outside the realms of DIY.
Can not understand woody, why you said So!!! when in the next breath you say, and we quote, Yes, we've done highly engineered beams and rafts and ground alteration to bridge sewers. The concept is to remove direct loading above and at the side of the pipe, but at what point does the amount of design and expense make it impractical and infeasible?
If you have done it, and already know the concept, beggars belief, why you still want to know how?
The additional expense is the clients decision. Nothing to do with us.
Regards oldun

 

[noseall]

If you want to know how to build on top, then say so,

I think you missed the joke there Old Codger.

 

[^woody^]

The old dude knows so much about building, he has had to use his prefrontal cortex for storing foundation details instead of humour recognition