Help on foundation

[Kelvin S]

I am looking for help on what my existing house foundations could be. I have dug a trial pit on the corner of my house as I am looking to do a small double storey extension and have come across this below. Any idea of what this could be and what I need to do for my extension? It is concrete and it angles into the ground. It is possible that the foundations is piled.

[Kelvin S]

Any other pictures needed please let me know.

[saveasteading]

can you show this from further back, for context? Is it concrete?

[nod]

Get you Building Control out and he will tell you how deep you need to go 

Then come and inspect before you pour the foundations 

[MikeSharp01]

That looks like slate slab it is standing on! How old is the property? 

[tonyshouse]

+1for building inspector,  lots of could be’s too thin to be footing concrete, could be the top of pile, then the slab on top of it looks a bit thin at about 225mm but with plenty of piles might be ok 

 

can you get original plans from the LA - would be worth paying for 

[Kelvin S]

It is concrete. I got building control and there were not really sure and find out by starting the extension. Don’t really want to start the work until I know how much the cost will be. The house is only 20 years old. Any suggestions or advice would be helpful. 

[Mr Punter]

Because the house is fairly recent, if there are no signs of movement on yours or any neighbours you should be able to use the same foundation type and depth as on your main house.

[Kelvin S]

Yes but I am unsure what type of foundation has been used .. or does it look like mini piles, strip foundation 

[tonyshouse]

Can you dig a bit more under find if there is a pile there, it might be offset a bit so poke for it first, interested to know the diameter 

[saveasteading]

Is that concrete under the main brickwork? If so then it looks to me just like a slightly bodged pier footing. As if they had forgotten the pier,  scraped a bit of earth out and put concrete in it.

If not that then a bit worse, a bit of masonry in the hole on a bit of an angle then spare bricks then the proper wall.

Poss just a skin of bricks against the main wall until up past the concrete.

Prob ok to tidy it up, and infill with concrete under it, 'vibrated' in well with a bit of 2x2.  

BI can look and prob agree to that or other pragmatic solution.

[ETC]

Your BCO will be able to check their records to see what was built. The the records should be in the BCO archive. The BCO will more than likely ask you to excavate your new trenches lower than the existing house foundation and the type of foundation should be determined by the ground conditions. If the BCO thinks you need anything other than a standard strip foundation you will be asked to get a SE to look at the foundation design.

[Kelvin S]

Ok any possibility that this could be piled? That is my only worry and having to pay extra costs that I has not budgeted for 

[markc]

I doubt it is piled, looks like a shallow strip found, sadly many larger developments have been getting away with pretty poor foundations. I’ve seen loads recently that are little more than scraped indentations (as opposed to trenches) with around 300mm of concrete thrown in.

I feel sorry for the buyer because they are likely to have major issues coming up.

[Mr Punter]

1 hour ago, markc said:

I doubt it is piled, looks like a shallow strip found, sadly many larger developments have been getting away with pretty poor foundations. I’ve seen loads recently that are little more than scraped indentations (as opposed to trenches) with around 300mm of concrete thrown in.

I feel sorry for the buyer because they are likely to have major issues coming up.

 

If the ground conditions are suitable, 300mm depth of concrete would be fine.  I think 200mm is regarded as the minimum acceptable but must be deep enough not to be affected by frost.