OT: Cost of underpinning?

[GB]

We have an old victorian house with a cellar and foundations a whole foot deep - that's 30cm for people who can't do imperial any more. The house is standing up fine despite that, but we are thinking of deepening the cellar to make it habitable. To do that, the surveyor advises underpinning to provide an extra foot of foundations. He estimates the cost at £500/ linear metre, which seems quite a bit to me for only digging down a couple of feet.

Any thoughts on this, please? I would add that this is not work we would contemplate doing ourselves. Also, we are in London, which might affect the price a bit.

[Huge]

IIRC when we were talking to our structural engineer, that's cheap. I think he was talking about £1100 a metre.

[Tim Lamb]

I know a friendly groundworks contractor who specialises in this sort of thing. Hand dig with air spading. Mostly work for insurance companies dealing with actual subsidence but also those well to do folk who have retro-fit basement cinemas in their London mansions.

Roughly whereabouts in London and can you get a skip close?

regards

>

[The Natural Philosopher]

Lucky you. £1000 a meter is more the cost here, on boulder clay. eed to go a biot deeper usually I guess.

Dont piss about. Underpinning is skilled and heavily manual work. You can only do it a bit at a time. because you have to dig out UNDER the existing foundations, fill with concrete, then wait then dig teh nect bit out. You cant magically lift the house, strip dig with a machine and fill and then plonk the house back.

Its pickaxe and shovel work mostly. Often you cant even get more than a barrow of cement near either.

Bite the bullet and do it, or abandon the project.

[Matty F]

A wooden house along my road was raised in one piece. They slid steel beams under the house and had hydraulic pipe jacks that could lift up a few metres, on the ends of the beams. All the jacks were connected with long pipes to a truck that pumped them all up at the same time.

[GB]

Finchley, and if we dig the front garden out first, it should be possible to get the skip extremely close indeed.

[Tim Lamb]

In message , GB writes

Convenient. He is based not too far from Hatfield. I'll try to find out if he would be interested, tonight.

regards

[The Natural Philosopher]

Aden house is

(a) light and (b) has some inherent structural integrity.

Yes it can be done..are they not doing something like this is Pisa?

But it takes more than magic :-)

[Tim Lamb]

In message , Tim Lamb writes

Right. Busy but interested:-)

Give me a mail addy and I'll pass on his contact details.

regards

[Roger Chapman]

A wooden House?

If you mean the leaning tower ISTR a report a few years back that they were experimenting with freezing the ground on one side in order to reduce the tilt but that hopefully is intended to stay in the same place.

Much closer to home there was that redundant South Coast lighthouse that was jacked up off its foundations and dragged back from the brink. Not magic but some serious money required.

[The Other Mike]

12 years ago it was GBP180,000 for 55 ft

[Tim Lamb]

The soil scientist responsible for Pisa lives locally. AFAIR the intention was to stop it leaning further and the cure was a huge amount of lead carefully positioned in the basement.

regards

[Tim Lamb]

Unfortunately the actual digging/filling costs are likely to be submerged in overheads. Somebody will have to take responsibility for design and implementation. His insurers need paying!

I had some engineer specified concrete pads laid under the brick foundations of a Victorian barn here. The pads are intended to support a steel frame carrying the weight of the loft floor and roof.

The holes were hand dug, roughly 1m cubes, back filled with barrowed hand mix concrete. Labour cost per hole was less than £250.

The job was inspected by building control but did not involve insurers or architects etc. because it is agricultural and not a dwelling.

regards

>