I'm looking at buying an old cottage which has had a small extension at some point (3m x 4m). The cottage is a total restoration project which is not a problem but the extension is falling away from the house (crack is about 5mm at top and 3mm at bottom on both sides). I know I should run a mile but the cottage has somehow won me over despite it's potential to bankrupt me-just like the FL2 own!

Has anybody had any experience of subsidence and the cost to investigate the reasons for movement or alternatively the rebuild cost for an extension of similar dimensions? I've searched the net and it would appear 1000/m2 is roughly the going rate for rebuilding which would bring the rebuild cost in at 12k which seems quite a lot.

Any advice would be much appreciated.

Maybe it requires under pinning? My extension 4 years ago was 28 grand, that was just the shell with windows and doors fitted and it was 11 m by 4m. Maybe best course of action is to get a builder or surveyor to look at it first before you put an offer in. Or obviously put a reduced offer in because of the subsidence. Is it in an former coal mining area? Black MY2013 SD4 GS Auto, Wood Company Armrest, Freel2 sticker.
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1000 per m2 is about the going rate for an extension to an existing house.

Why not just demolish the old extension and refurbish the cottage to a decent standard, then you can add another extension later? There could be other reasons for the cracking, like sub-standard foundations. If the cottage is ok then subsidence may not be the issue. Always get a survey though.

LoP

Many thanks for your help. A previous buyer has had a survey and pulled out-more due to the cost of the refurb than the subsidence. The owners of the property have got a copy of the survey and it has recommended further investigation. Having already renovated one property we are fairly experienced and I must admit when I was costing out the work for this one I did consider pulling the extension down and focusing on the cottage. Having gone for a second viewing, however, I thought I might get a structural engineer in to offer further advice. My concern is that a single visit would not throw any more light on the matter though and it would be money wasted.

Could be the extn was a bodge job and not had proper foundations done first. If just a shallow float of concrete was put down first and not reinforced could be the reason for it coming away from the house. if this is the case which isn't that hard to check the best bet would remove the extn and start again.

You could check with the council planning dept to see if planning approval had been given for it, I suspect no planning permission had been given as each stage of build has to be passed before the next stage can be started
and that would be my first check anyway. No council would pass a poor building base.

When I built an extn I had to go at least 6 inches under the house foundations and the wall had to sit on a concrete base 3 ft deep (london clay sub soil) and extend at least 6 inches beyond the wall width.
Another problem was the long wall was right up against next doors high wall with just a 6 inch gap seperating them. So I had to put supports in to stop that falling in on my foundations. The supports were roof timbers from a well known very old local cricket club being demolished and just the right length, here again begging did the trick but I won't say how I got them home, my secret


. My building inspector first checked the support for the outside wall trench was deep and wide enough before letting me fill with concrete, which also entailed moving a drain pipe which had to be bridged and pea shingled for protection. Next inspector came and checked the concrete was wide enough for the support wall and the floor area was properly done with damp proof membrane etc on a sand base with steel mesh, the wall had to be have a damp proof course as well. Next check was when I built to window height then roof height followed by roof joists which he wanted on hangers but the house wall bricks had been put in and a very week cement "wash" so allowed a half brick from house to be removed and the joists inserted. Then came the roof with furloins? with the correct angle for the flat roof to slope properly.

only then did the inspector sign the job off when the roof was finished One tip I was given as an amature DIY builder was to incorporate in the plans "all dimentions to be agreed on site prior to commencement"

Why? For people like me it allowed me to be slightly out on measurements if that occured and didn't have to go back to have planning approval again. A professional builder would not be given that flexability.

Just one other point. As it was built on the side of the house and with a door to the garage, that door frame had to be a fireproof frame and door.

Did it all myself and hard work by hand. Yes it was very hard work but in truth enjoyable, the best part was laying down the final floor tile and grouting in, then cleaning of surplus grout and looking at the final completion
9ft x 18 ft if I remember correctly inside ,1 wide window and 2 doors had gas fire fitted as well while the build was going on, gas fitter did that, and that was the only thing I didn't do.

Total cost then in the 1970s was well under £2000 completed.

That was for concrete -drain pipes and supports- pea shingle-damp proof membrane- steel mesh for floor area- sand-bricks-doors and frames- Windows and frames-roof timbers and finish (had professionals to seal it) removal of clay- tiles and grout- gas fire and fitting

I did have the cheek to go onto a building site ask and saw the site foreman if anyone could help with cutting an earthenware waste pipe. Not only did he get it cut on the marks I made on the pipe but wished me best of luck and well done for having a go, which I thought at the time was very nice of him Ex 2010 Freelander2 GS-e Diesel manual Silver owner

Labradorslave wrote:

I know I should run a mile but the cottage has somehow won me over despite it's potential to bankrupt me-just like the FL2 own!

advice would be much appreciated.

At least it hasnt got a clutch, unless its the one that grabs you by the googlies

When the extension on my parents house developed cracks it had to be monitored for quite some while (they stick a ruler on the crack) to determine whether there was any further movement and to what extent before deciding on any further action. In the end it was necessary to fit a floating floor (I think that's right).

So as others have said, it may not be possible to determine if it's subsidence from a brief examination, unless an expert can tell, I wouldn't know.

My advice would be to put pressure on the sellers to use their buildings insurance to pay for the repairs now, before you buy it.
When we were buying our house the survey showed settlement - distinct from subsidence and not as serious. A further "trial hole survey - £250" showed it was a rainwater drain leaking underground that had washed away fines in the sandy sub-soil. Estimate to repair foundations was only £1200 but the current owner ( actually, the estate of the deceased) claimed on their buildings insurance before we bought it. It added 6 months to the process but ths should have been less really.
The big watch out is future insurance. Our isn't "rated" by the insurer but we stayed with the previous insurer who had paid out on the repair and we've been warned when thinking of moving insurers that a settlement or subsidence history will ring alarm bells at most insurers. it makes me laugh when offered a quote when at the bank counter - just mention its had settlement/subsidence and they soon shut-up.
Hope this helps. FL2 2007 57 GS
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Thanks so much for sharing your experiences. My gut feeling was to leave it well alone but at the same time I want it! Unfortunately the current owner does not have house insurance (he bought the property for the land it came with which he has divided up and plans to put a new build on for himself-well away from the cottage I am considering buying). One of the drains did look blocked so the subsidence could be down to that but there were also a number of rather large tree stumps near the house so the reason was not clear. My gut feeling was that it would take several months (and no small amount of money) to find out the exact cause. I think given the uncertainty I will let this one go. Thanks again for your help.

Sorry to go on with what may be a lost cause but if he bought it with a loan or mortgage they would have insisted on buildings insurance. FL2 2007 57 GS
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sounds like the main house is ok with no subsidence, so problem only lies with the extension.

probably a bodged job with sub standard foundations ?

if you really want the house I would buy it and demolish the extension and rebuild properly to your own specification.

still it wouldn't do any harm to get some kind of survey done before purchase, even do it yourself and dig down around the extension to foundation level.

Iain

Im a BCO,

it could be the extension has decent foundations, and the house has settled more,
I would spend the money on a structural engineers visit/survey,

it could be the best few hundred you ever spend.

if it needs underpinning, its a low tech job just digging and concreting, you and a few mates could do it in a weeks holiday.

If as you describe, 'it is an old cottage' and its in Derby suburbs then I'd put a 95% probability that the cottage has no real foundations .
Typically they a that time just dug down a bit and put flat stones down that were wider than the intended wall.
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Our cottage near Belper dates to 1800 and has no foundations. We have been on the house for 37 years and nothing had moved. Our extension was built 30 years ago with ginormous cast comcrete foundations and shows some minimal settling!
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I would suggest to get a professional to establish which is moving and why.
,
Kind regards from Fred 2010GS Auto ex Celeb, Santorini Black, 2011 facelift , spoiler, spats, mudflaps, LED footwell lamps, Witter detach,
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The chances are that the extension is not on foundations and just built on, 5mm and 3mm ain't bad tbh, easiest way is dig down the side of said extension and have a butchers.

Underpinning even cantilever may not be required, it may just be natural settlement, if you by the house put makers on the joint and record the gap over a 6 month period and see if it moves, if not mortar up and relax, if it does then look at underpinning. My11 freelander 2, xs, Manual, 18" hse sparkles, sidesteps, privacy, zermatt silver metallic, almond nutmeg alacantra, twin electric towbar

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