Ground Survey Help...

Hello All,

I am in the early stages of starting a side extension on my home. We know our house is built on piled foundations and ring beam, however, the plans from that were released to us from Barrett Homes (house approx. 12 years old) shows the layout of ring beam and piles but no associated measurements of depths etc.

We recently had an architect and structural engineer visit the property and concluded that before any plans are drawn it would be best to conduct a ground survey to locate the depth of the ring beam, location of drains and pipe size and type of soil.

Estimated cost of the top of there heads for someone to do this this was up to £2500.

They did stress that this survey was optional but would be preferred by them so they know what they are dealing with.

My question; is there anything I can do to minimise the cost of this? Or are there other options where I can find the information they are looking for from other records?

If I clear the land and dig a trial pit, dig down to the waste pipes (toilet waste) and expose them clearly, would this minimise the cost? They did mention that an auger would be needed to bore down for soil samples, which I cannot do but if there is anything I can do I would be grateful if someone could shed some light.

Thank you in advance.

I think digging down yourself would save a lot, most of the cost of the survey would be labour costs and reinstatement. If you engage a surveying company and ask the breakdown of costs then offer to do the expensive bits.

Thank you for your reply John,

Just out of curiosity, do I need to serve an Excavation Works Notice to my neighbour when digging a trial pit? My neighbours foundations are about 4 meters away from where the trial pit will need to be dug and the drains are 3 meters away.

I don't want to miss something and get in trouble for it later!

Yes get your spade out and some detective work will likely establish the drains. And don't bother with an architect for an extension, find a good architectural technician.

We had to have a soil survey done and I seem to recall even with the soil analysis lab work it came to about £1450 . That was a new site, so no locating drains etc though. As said above, foundation depth just needs a spade! Quite seriously, have you thought of dowsing for the drain locations? I do it regularly and it works - I've no idea how it works, and I'm sure it's not some supernatural nonsense, but its located drains for me even when I've been convinced its wrong - have dug down and found a drain where I least expected it. I just use 2 bits of wire coathanger. It was taught me by a farmer when I was a kid and we were looking for a field drain (he used 2 bent welding rods) . Doesn't work for everyone - my daughter can do it too, but for some reason it doesn't work for my wife.

Why do you need to know the depth ect of the existing foundations?

Surely all you need is new foundations designed for the extension.

Hello everyone,

bit of an update; my architect has come back quote £3500 for a soil test. Yikes! He seems to think that 20k on top of that will get me to DPC level. I'm starting to think I'm in the wrong job!

^woody^ - apparently they need to know how far down the piles need to go before they design them. I have managed to uncover the foundation design of the property from Barrett Homes. It gives the dimensions of the the ring beam, steel reinforcement placement and the loads each pile under the house can take but nothing on the depth or size of the pile itself. I even have the drainage maps.

Am i crazy in thinking that a piling company with an in house SE should be able to just come here look at the current foundation design and tie into it with the same method? The house is currently 3 storeys tall and I am looking for a single storey side extension.

I have read from other people that the pilling contractor will find the depth the pile needs to go when they start boring out the ground. If so this soil investigation seems unnecessary.

Any views?

Paul Armes said:

^woody^ - apparently they need to know how far down the piles need to go before they design them

Click to expand...

Exactly. And they do that by boring the ground. This has no connection at all with the existing foundations.

freddiemercurystwin said:

don't bother with an architect for an extension, find a good architectural technician.

Click to expand...

You can lead a horse to water ...

You don't need to expose a drain to work out its line, size and depth either.

A simple CCTV survey would show you where all the connections are and if there are any suprises like buried man holes etc...