Buying & Extending House with historic subsidence & underpinning

[Buddy101]

Hi - we’re quite far a long the process in buying a suitable family home for us when it comes to light that the house had subsidence and underpinning was done in 1997.

We’re struggling to get insurance as we don’t have a Certificate of Structural Adequacy as the work was done before this existed. We do however have a Certificate of Practical Completion. We have had a Homebuyers RICS survey and a drainage search and it’s not returned any issue.

We don’t know whether the difficulty in getting insurance (reasonably priced) is a red flag and whether we should walk away?

We weren’t worried before the insurance thing because we thought it has been more than 25 years and there’s no signs of issues and I guess a house that has had it done is a better proposition than one that hasn’t. But now the insurance premiums are sky high it’s causing us to stop and think. We’re going to get a structural engineer to go in and survey that it is indeed historic and nothing current.

We entered into a bidding war with 9 others and it ended up with sealed bids -none of us knew about the historic subsidence - I wonder if we had all known whether there would have been less interest/ we’ve offered to over pay quite substantially!

Finally; the house is okay size wise but our intention was to extend within 2-3 years…we’re now worried we won’t be able to afford to and that the costs will be higher because of underpinning. Has anyone got experience of this ? Will it be more difficult to extend ? More costly?

As always, any help and advice however “obvious” it might be, please share as we’re in unchartered territory here and grateful for any help!

I'd run for the hills tbh
Sorry op

Wouldn't touch it, sorry. It should have been declared earlier in the process.

Sorry but I would run away too.

Partly because I would be worried about resale. But also worried about the house starting to sink or something

Doesn't it have to be declared from the outset or is there a time limit on that? I've seen a couple of underpinned houses advertised and it's in the details on Rightmove!

Owner of a previously subsided house here. I really wouldn't touch it for these reasons:

1. The vendors and their agent have obviously been less than open about its history - you could go on with your buying journey and then much later down the line find something that you're not willing to risk and have to pull out when you've already spend a lot of money on it.

2. You've engaged in a bidding war suggesting that you might well be paying over the odds for a house which should be worth less than you might expect a similar home to be, given its structural history.

3. Even when it's all fixed, you never lose the fear of something going wrong again in future. Every little hairline crack which appears, every time a door or window sticks - it's a stressful existence living in one! Plus there is all the uncertainty of how to market it when you want to sell it.

Oh and re. extending - every time you do something structural you risk opening a can of worms as the building shifts on its foundations.

@Buddy101 I assume you have bought it if you are insuring it. Why didn’t you keep the vendors policy going? Who did they insure with? Was your sake subject to survey?

Also some of the above is total rubbish. This house is probably structurally sound. It’s had the work done! What evidence have you seen that concerns you? Further cracks? Wonky windows?

Negotiate with a decent insurer about them accepting a report from a structural engineer in lieu of more up to date documentation. If it’s structurally sound it’s perfectly insurable. There really should be no major issue . You should possibly avoid some insurers.

Subsidence means a wall has moved (sunk) because the foundations were inadequate for the ground conditions. A concrete raft has probably been inserted under the wall to stop further movement. Any decent structural engineer will ascertain if this is continuing to work. It’s unlikely it’s not.

As for extending? Why could you not? It just needs suitable foundations designed for the ground conditions. It’s hardly that difficult!

@Kat2328 Total rubbish. DH is a structural engineer and houses do not move on foundations! Unless owners damage the house of course and don’t understand how the structure works.

The important thing is the design of the foundations but houses don’t move unless the foundations are wholly unstable. Mostly they are not.

thanks @TizerorFizz

We haven’t purchased it; we’re just getting ready to Exchange contracts and so looking into insurance now before we exchange.

The existing insurer is no longer selling home insurance; we’ve tried !

We’ve not seen anything that concerns us; we’ve had a homebuyers survey and a drainage search and nothing horrifying came out. I guess it’s just that it was a “secret” until the last second that’s the big concern I guess but maybe from their perspective it happened more than 25 years ago so maybe they didn’t see it as a thing.

We haven’t got a Structural Report from an engineer yet so I think that’s our next step.

I was worried that by digging foundations for an extension it might dislodge something in the main house or that we might need deeper foundations because of it … this coming from a complete novice who knows nothing about doing extensions though !

I considered a house with subsidence history- it was in the listing on Rightmove.

Houses with this usually sell for less.

Ruuuunnn it is worth much much less because of the subsidence and especially with the insurance issue. Are you buying cash? Because otherwise your mortgage company may not want to proceed. The seller and agent have been dishonest. You'd really really struggle to sell on and it's not your dream house anyway

@Buddy101 First of all, in some areas lots of houses have been underpinned. Very much depends on soil and age of house. They don’t sell for less in desirable areas. So are you saying the house is not insured at the moment?

Definitely get a report from a fully qualified structural engineer before you proceed. Make sure they inspect every wall for faults.

Regarding extensions, make sure a structural engineer is involved in designing the foundations. Extensions have to join existing buildings and how foundations and walls are connected is their job. You don’t want an extension moving away from the house but appropriate design will ensure all is as it should be. We have 6ft foundations in our extension due to soil and a tree nearby. One part of the existing house has shallow foundations because it’s old. Other foundations are almost certainly not 6ft. An engineer will know what to design so the house is structurally sound.

However you do need to ensure it so maybe ask a broker about non standard houses?

No experience with an actual house with subsidence but I deal with this in my work.

Some insurers may exclude subsidence cover all together, others may want to see a recent structural survey confirming all is well.

Personally, unless the house was literally my dream house, I wouldn't touch it.
But plenty of people do.

Thanks again.

The house is insured by the vendors atm - but the insurers are not taking on any new policies atm.

I think what you’re saying is true - I’ve spoken to a few estate agents and they’ve told me about 50% of houses in the area have had issues which makes me think atleast we’d be buying one that has been underpinned as any other in the area might be a ticking time bomb -

We have got some quotes but we’re looking at £1600 per year as opposed to the £700-800 we were expecting (buildings and contents).

@TizerorFizz Do you think that the extension will be more expensive because of it?

Thank you.

It seems that not many of you live in areas with clay.
Subsidence and underpinning is the norm in this part of SE London. And houses are sold and bought all the time with no running for the hills .

@martellotower Exactly.

@Buddy101 You need foundations designed regardless of historic subsidence. Should not be more Monera’s no extra work is involved for the engineer. There would need to be a ground survey and foundations designed but you need them anyway!

Given how much insurance has gone up, that’s not wholly unreasonable. What calculations are you using for rebuild and professional costs? You might be able to negotiate down with a structural report.

Yes very common on clay. Speak to a local structural engineer

If it was underpinned in 1997 then I'm surprised that it's proving quite so difficult to get insurance. Our house was underpinned at about the same time and we stayed with the same insurance company for many years until my husband forgot to renew the policy about five years ago and it lapsed. We did find that some companies weren't prepared to insure us but others were prepared to because the work had been carried out over 15 years ago and a couple of others woukd have been willing to inside us 20 years after the work - obviously if there had been no further obvious movement.

I don't know if it's still the case now but I was told at the time of our subsidence that the existing insurer was obliged to continue to provide cover, and this included insuring a new owner, so it might be worth contacting your vendor's insurers.

Historic subsidence wouldn't necessarily put me off buying a house and it would depend very much on the cause. My husband, who spent over 50 years as a surveyor, has always said that he doesn't have s problem buying a house thst has been underpinned because it's very unlikely to move again!

Oops sorry, I just re-read your lost and saw that you have already checked with the existing insurer.

@Growlybear83 A house that’s been underpinned is likely to be more structurally sound than one that hasn’t in some locations.

@Buddy101 My proof reading failed earlier! Basically you need foundations designed regardless of whether a property is underpinned or not. Just think of underpinning as a raft of concrete under the house stabilizing ground conditions.

We have underpinning and are insured with
https://www.adrianflux.co.uk/
We got a good deal with them for the first year but their rates have now shot up .

@martellotower - can I ask how much they’ve jumped by please? Is it just because insurance costs have gone up or more they’ve got you in their hood and can charge what they like? Interestingly they’re the people who have given us the most reasonable quote but I am worried about what happens next year and the year after ! Thanks for your reply.

It was £700 in 2021/22
£1100 in 2022/23
£1400i n 2023/24
this is still lower than our previous insurer.

Should have tagged you @Buddy101

For context ,above is for a 3 storey ,c.1910 brick house. Semi detached with other property underpinned before our half.
On a slight hill, large back gardens , trees , heavy London clay.