Period Foundations

[skier-hughes]

Not terribly period but very pertinent to work we do, as we have discussed foundations and digging many times.
Those who run a business may also want to look at their insurance cover, or whether they have any and if they do actually need it........... of course you do!
http://www.expressandstar.com/news/2013/06/05/12k-bill-after-wolverhampton-house-collapsed-into-trench/

 

[elizabeth]

Wow! we will be extra, extra cautious when it comes to having a trench dug next to our wall (due to start next year). Did he undermine the foundations? We have to have soil removed which has been banked up against our wall to our house and then possibly create a French drain or preferably an open ditch, which has to be quite deep. Our wall is stone plinth with cob on top so we are using a builder who specialises in cob. Things could become unstable easily so having seen your clip we will take care and have props at the ready.!!!

 

[worms]

Interesting that the builder seems to have been representing himself in court and all credit to him that he held his hands up and accepted responsibility. However, I would have thought that if he was being represented by a lawyer there would have been questions asked about the adequacy of the foundations at number 69! I also wonder if any insurance would pay out where a case hasn't been argued in court by a solicitor?

 

[andrew gayton]

And the party wall surveyor said? :roll:

 

[andrew gayton]

http://www.hse.gov.uk/construction/safetytopics/excavations.htm

The angle of repose is the relevant consideration here.

 

[CliffordPope]

I'm intrigued by the theory of foundations.
Modern constructions seem to use a solid slab of concrete covering the entire area of the house. Presumably this slab sort of floats on the soil, so cannot give way unless entirely undermined so that it falls into a hole?

On the other hand a trench must rely on pressure from the surrounding soil?

Our house, late Victorian farmhouse, has no foundations at all. The stone walls just seem to rest on the ground. It's quite easy to dig a tunnel right under the wall by hand with a trowel to pass services through. Perhaps it's the other walls that hold it together, like a house of cards?
The thinner internal walls too just sit on soil, but presumably don't fall over because they are linked to other walls and the ceiling.

 

[andrew gayton]

I'm intrigued by the theory of foundations.
Modern constructions seem to use a solid slab of concrete covering the entire area of the house. Presumably this slab sort of floats on the soil, so cannot give way unless entirely undermined so that it falls into a hole?

On the other hand a trench must rely on pressure from the surrounding soil?

Our house, late Victorian farmhouse, has no foundations at all. The stone walls just seem to rest on the ground. It's quite easy to dig a tunnel right under the wall by hand with a trowel to pass services through. Perhaps it's the other walls that hold it together, like a house of cards?
The thinner internal walls too just sit on soil, but presumably don't fall over because they are linked to other walls and the ceiling.

modern buildings can be built on a slab with a thickened toe to the perimeter, but most rely on trench foundations and slab. Remember that houses built from flexible materials can take up distortion/s much more readily than those built from less flexible materials.

 

[Zebra]

The angle of repose is the relevant consideration here.

I think I shall be considering my own angle of repose quite shortly. Something in the region of horizontal should about do it....

 

[Feltwell]

Never mind the angle of repose, it's the angle of dangle that needs careful consideration you know.

 

[LadyArowana]

The angle of repose is the relevant consideration here.

I think I shall be considering my own angle of repose quite shortly. Something in the region of horizontal should about do it....

Sounds like you might be performing some covert slump tests there, and you had us all fooled into thinking that you were a fan of traditional materials.

 

[Feltwell]

Wow! we will be extra, extra cautious when it comes to having a trench dug next to our wall (due to start next year). Did he undermine the foundations?

Ideally, you need to avoid digging out the area that slopes out at a 45 degree angle from the bottom corner of your wall or foundations, if you have any. Avoid this and you should be safe.

If you have to dig into this area then the usual process would be to dig out a short section (about 3' generally), do the work you need to do, back fill the trench then do the next short section. I've done this when putting in modern concrete foundations and it works fine - but if you're backfilling to create a French drain then it won't be so easy, as the material going into it won't be compacted to support the wall as much as the original material, and 3' sections aren't exactly convenient lengths for laying a pipe in the base.

Really what you need is a good, experienced builder, who will have a good judgement of how much material he can safely remove. Sounds like you've gone down the right route in getting a cob specialist rather than just a normal groundworker.

What you don't do is what matey in Skier-Hughes's link did, and dig a whacking great trench right next to and below another building, and then leave it open overnight! You would have thought at the very least he would have dug it at the last moment before laying the concrete. Really he should have done what I describe above and dig it in short sections only, laying concrete in each and letting it go off before digging the next.

 

[elizabeth]

Thanks Feltwell for your thoughtful advice - it's definetly worth our while using a specialist, we are far from knowledgeable and a cob specialist will understand the medium as to whether it will be unstable during excavations. It maybe, when the soil is removed, all that would be holding it up is the terrible cement render. (which will be coming off in the future). Plus we are uncertain if a French drain will even do the job. Ideally the best situation would be to have a 3 foot wide trench along the length of the wall without any back fill, allowing air to circulate and to slope the trench so that it drains away aswell as using a hose with slits in. All this is in planning stage. Did you need to create a drain yourself?

regards
Elizabeth