Single storey rear extension foundations. Piled?

[burts]

Starting my extension I dug an inspection pit along my garage wall which I will be building alongside. Trench was 900mm deep, with 450mm of concrete. It had a tough black plastic sheet running down the side of it, around 15mm thick. Building inspector seems to think the foundations are probably piled. Suggested an earth test to see if the ground is suitable for strip foundation, how much? Where can I find someone?

Other than finding an actual pile, any other tell tale signs of foundation? Any site I can find the plans on the
Build, site is only 12 years old. Taylor Wimpey. They were unhelpful.

Will piling cost loads of required?

 

[noseall]

Will piling cost loads

Yes. About three times the cost of strip, if you're lucky.

 

[noseall]

Other than finding an actual pile, any other tell tale signs of foundation?

Any photographs?

You will either have a strip, piles or raft foundations. All should be identifiable with an inspection pit.

 

[burts]

Thanks for the replies.
The inspector said it’s probably pipes but will need to dig more holes and one next to the house to confirm.

I can forward a photo later.

3x the cost and I doubt it’s worth doing.

 

[wessex101]

Probably the most important piece of information you missed out was what was the ground like at the bottom of the test pit?

Is it good firm undisturbed ground? or is it fill with bits of rubbish and old demolition debris? or is it soft maybe peat or soft sand? At least give us a clue so we can have a stab why the existing property might have been piled. I'm surprised the Building Inspector did not say anything about the ground in the test pit.

In answer to part of your question you could get a geotechnical survey done, it can check the ground bearing capacity and take core samples at depth to check the underlying sub-soils, depending on the complexity it can range from £500 to £2000.

As for checking the records of the original build. You could ask the Building Inspector if it was a site inspected by the Council in which case the foundation inspection will be available for public viewing. However, with a big national housebuilder it is more likely the inspections were carried out by a private inspector and I do not think their inspection records are available for public scrutiny.

 

[burts]

The inspector did didn’t seem to care about what was in the bottom of the pit.
When digging it didn’t seem sandy, was a little bit of clay I guess but nothing major. I did come across a fee bits of hardcore.
Just been told an earth test is £1850!!!!
I can’t justify that.

 

[Notch7]

I heard from a builder that new builds are now quite often piled in order to comply with the projects insurance scheme, ie NHBC or the like. That could be a regional thing of course.

 

[burts]

Ok, so it might have been piled for insurance reasons and not because it had to be. The building contractor are being very unhelpful. I’m at a dead end at the moment

 

[^woody^]

If it's piled, it's piled for ground reasons only not insurance.

Are there no other extensions on the state that the inspector can refer to?

If it's piled you should be able to see the pile caps at a fairly shallow depth. That 15mm board may be just for the clay, or something else.

 

[noseall]

3x the cost

Foundations only of course

 

[burts]

Foundations only of course

I know but it still won’t be worthit for what I’m achieving

 

[burts]

If it's piled, it's piled for ground reasons only not insurance.

Are there no other extensions on the state that the inspector can refer to?

If it's piled you should be able to see the pile caps at a fairly shallow depth. That 15mm board may be just for the clay, or something else.

There has been 4 others completed but the sure is down so I can’t access the plans etc. I’m waiting for someone to call me back who would have signed these other extensions off.

The 15mm May be for the clay.
Guess I need to dig some more to check if no one gets back to me

 

[Leofric]

If it was built by a large housebuilder it could have been done under NHBC Building Control . You could try contacting the local NHBC office but they won't be obliged to provide you with information on the foundations but might be helpful if you ask them nicely.

 

[burts]

Well this is all in vein as planning on the final day half hour ago have sent an email saying the proposal under neighbour comsultion is refused.
It’s sinhle storey 6m our 4m wide but connecting on to my garage wall which is about 1.5m of the rear of the property. Saying it’s then classed as a side extension and the width being more than half the total width of original dweliing is not allowed. Ffs
I can’t step it in as it’s not possible

 

[Leofric]

Doesn't this just mean it can't be done under permitted development rights or the neighbour consultation scheme ? That doesn't mean you can't apply for planning permission to have it considered as a formal planning application . It could still be refused of course, but try asking a local friendly architect or architectural technician for some preliminary advice on whether they think it might be possible to obtain planning permission for an extension to suit you.