DIY Doctor

Centering wall on house foundations

Postby astate » Sat Jun 16, 2007 7:35 pm

Read the previous posting with regards centering the wall on a garden wall foundation. My question is related but concerns foundations for a house.

I currently have a contractor building a large extension at the back of the house. He dug what seemed to me to be extremely solid foundations onto good rock (chalk). However, when he started laying the brick work, the outer layer is very close to the edge of the concrete. The foundations aren't really strip, but vary between about 900mm and 500mm in thickness (the site slopes a bit). Their width is 600mm. On one retaining wall he has laid blocks within 6cm of the edge of the foundations. This wall will be about 5m high (the bottom courses are heavy aggregate (?) slabs laid flat, above the DPC I believe he will be using lighter blockwork. (NB This wall probably has foundations at the thinner end of the range).

I have read that for strip foundations the walls should be centered. However, does this apply when the foundations are very thick?

I have tried to find resources on the web to read up on this without success. Any advice on a useful reference?

Any insight would be appreciated.
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Simply Build It

Postby thedoctor » Thu Jun 21, 2007 8:22 am

See our project on foundations all of the guidelines are in there. If you are worried in any way you can call the building control officer for your job, her will be required ( He should already have been oin site to pass the foundations) to visit the job about 9 times during the course of construction but he will only look at the ground just befoire the foundations are poured and then again when the walls are up to DPC level, by which time the top of the concrete will probably be covered so he will not see how close the wall is to the edge but, again, if you are concerned, please give them a call. It has been known for building companies to set out buildings incorrectly and rather than go to the exopense of moving the foundation, or extending its width, they will build on its edge. This is not acceptable unless the building has been designed this way and has ring beam, or other construction details built into the plans to allow for, say, drain pipes passing very close to the building.
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Postby pedro » Wed Sep 26, 2007 7:42 pm

I have builder doing a base for a conservatory, he is doing his own thing with complete disregard to drawimgs. the main problem is the shallow depth of the foundations and the blockwork running off line with the founds,with the result that there is a foundation projection of only 20mm instead of 150mm either side of the blockwork sitting on the founds. I stopped all work and the rep from the nation wide conservatory company( the builder is a sub-contractor) arrived to see for himself. The result is that they are coming back in a couple of days to demolish what he has done and dig out the shallow foundations and start all over again. I requested that they bring in another builder but they say they are obligated to give him the chance to correct his unacceptable work. There was a whole list of other things he was missing or taking short cuts with so I will be watching very closely next week.
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