Is subsidence a massive deal in London?

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Just got the survey back on our new house, stating that we should get a structural surveyor in to check for subsidence. There are cracks around the bay. It is a 1910 house and is on London clay.
If it is subsidence, do we find out how much to underpin?
Is underpinning always the best treatment? the cause would probably be the clay, as no trees near by.
Not sure whether to be freaked out by this and think about pulling out, or whether it is a just a fact of London life, and go ahead anyway.
What do you think?
Thanks in advance.

I live in London and don’t have subsidence. Can you get a mtge without the check?

What kind of survey did you have done? On a house that age I would always get a full structural report done. We are not in London but our local searches flagged the house as being in a high risk area for subsidence, but the map showed the whole city as being at risk. Cracks on a bay could mean many things. Probably best just to get the experts in!

Get a structural survey and then renegotiate on any remedial work needed.

If it needs 20k spending on It then you want this taking off the price or they can do the work and evidence this along with a guarantee.

It is because the house is on clay rather than being in London.

Thanks all - It was a homebuyers survey (level two) and the original mortgage survey didn't flag anything up.
Good idea @cabbageking I have seen that a structural survey could cost £500, so we might need to gauge whether they are willing to adjust the price based on the findings before going ahead.
As so much of London is on clay, you would think that this kind of subsidence would be quite common?

I’ve never heard of subsistence in London so presume it’s rare.

I’d also say that more buyers would run a mile when they hear about it so I’d expect a heavilly discounted price for the property. I think that even when you’ve done the remedial work, you’ll need to disclose that to future buyers (and it’ll put people off or they’ll want a massive discount).

You should refer back to the surveyor who carried out the original survey. Ask for more detail and suggest that you'd like a structural engineer to take a look.

Most surveyors aren't structural engineers, hence why the term Full Structural Survey was changed to Building Survey quite a few years ago.

As for the cracks, bays of that age often don't have foundations. This means that they can easily crack at the abutment with the main wall, especially on the upper floor. The bay has been there for over 100 years and will likely continue to move but underpinning may be the solution.

The trouble with clay is it can absorb lots of water. When it does it expands, pushing on foundations and floors, called heave. The opposite happens in the summer, it dries out and shrinks, potentially causing subsidence. This continual seasonal movement is common, especially after some of the recent hot dry summers.

Hope that helps.

If you can fit a coin in the crack and they are following a diagonal line along bricks they say it’s a sign of subsidence

If it’s a rendered house and just has cracks appearing it’s just a sign they need filling and redecorating as render will crack over time

Clay does expand and contract, the times when clay can cause bad enough subsidence to require underpinning or other remedial work is if there are trees too close that could be isi g all the water in summer otherwise the general expansion and contraction over the seasons aren’t anything to worry about

I had an insurance assessor to my house at the beginning of the year for a leak claim and we got chatting.

She told me that in our area (Hertfordshire border of London) the highest number of claims is for subsidence .

I was surprised but she said it was due to the really hot summer we had had before and the clay earth in the area.
I said it sounds horrific and so much u see pinning.
She then told me that they didn’t use underpinning to fix any of it.
It was some sort of internal and extraneous stitch fix along the wall.
Less invasive and quicker and obviously cheaper.
Made it seem like something not as scary.

Thanks everyone, that's quite a range of responses.
You're explanation NemophilistRebel makes complete sense and bears out articles I have read on the subject. ie what SurveyorScott says about clay is changing throughout the seasons, and that. underpinning isn't always the solution.
JoJos reaction is one that I would assume that our future buyers might have, and worries me.

I will speak to the surveyor and get a building surveyor to have a look, just so we are forearmed.
Thanks everyone.

Just adding to what @NemophilistRebel says. It is common in North London/Herts. You see it in the houses from Highgate to Hadley Woods.
However do check if it'll affect the house insurance. I've seen a case where no-one except the company who paid for the underpinning would quote and they kept the premium high to recoup costs, even though in effect that horse had bolted.

Definitely pay for a structural survey (circa £800) in London. If it has subsidence, I'd walk away personally. You might have a problem getting buildings insurance (which would affect getting a mortgage if you needed it) or it might be very costly to fix and you'd need to declare it on selling which would put a lot of buyers off.

We're meant to be moving before Xmas - I think this is going to set us back quite a while.

Our Victorian semi has some signs and next door was rebuilt as a result of subsidence. We got a full survey and went ahead with purchase. It's insured, but I think a high excess so might be worth checking this if you are worried.

It is a problem in many parts of London. Suggest you get the full survey first but back out if it does reveals subsidence - buildings and contents insurance is expensive already in many parts or London due to crime: add on a structural problem and you could end up paying thousands a year (if you can be insured at all).

There are lots of Victorian properties that have had subsidence due to shallow foundations and clay soil. We bought one of them some years ago. The work had been done so as far as we were concerned the property was in better shape than neighbouring properties that were not yet done. I’m sure we’ll take a hit when we sell it but it’s since doubled in value and it’s a nice area so I’m not too concerned. One downside is we’ve stuck with the original insurer, should probably try and get a specialist insurer to quote but we didn’t bother. So buildings insurance is more expensive, which seems odd as the problem is fixed. If a house needed underpinning I’d probably walk away but if the work was done and insurer willing to continue then I’d buy it. As long as in sought after area. But you do get people who don’t know much who would panic about it. So I’m sure it limits the market when selling.

My house has a bit of subsidence, lots of houses around our area do, though it's not London. Mine is partly because of a tree. It's not actually that much of a deal living here, old houses have all sorts of cracks, and I read that in a seller's market it doesn't necessarily affect the price. Having said that the uncertainty about whether it is going to be an issue when I sell is a bit crap, so not sure I'd actually but something with subsidence. Though the bay coming away at the front of the house without anything else being wring isn't something I'd worry about, it's really common.

Thanks everyone. I've called the surveyor and waiting for him to call me back

On a 1910 house in London (ie high value) it’s definitely worth a full structural survey.

Subsidence - depends how much, what cause, etc. Not necessarily a massive deal. First step is to ask the vendors if there is any history of subsidence or suspected subsidence including insurance claims, investigations or remedial work. Then when you have your survey, ask the surveyor for as much detail as possible about the cracks, their cause, how old they are etc.

Our Victorian house in SE London had subsidence. Likewise a lot of people we knew in that area. It took us a long time to sell and people did run scared on it.

Pretty much the whole of north London is built on clay and I'm not aware of anyone that's had an issue (it's a bugger to do the gardening in - you literally get a clump on a shovel that looks like you can put it straight on a potters wheel!).

I had a property there too which I never had a problem with but I remember it being flagged as a possibility.

Given there are some cracks already though, I would recommend having a full survey, just in case.

In answer to your original question it's not a big deal in the sense that it's a common problem across London due to clay soil. I don't know much about North London but it's certainly a problem in South East London particularly around Crystal Palace area. We live in South London. There's a reasonable crack in our back wall which came up as nothing to worry about on our survey eight years ago. Also after the last two very hot summers a hair line crack has developed in the ceiling across our front bay window. It's often just movement rather than subsidence (as in the place is falling down). Full survey is always a good idea in any case.

Yy with miss also Forest Hill & Brockley dont know if it’s due to being hilly as is Crystal Palace or if south east London is generally more susceptible.

Spoke to the surveyor and the cracks aren’t quite where he would expect to see them. That’s why he thinks he R’s with getting the structural engineer in, so tomorrow we’re going to book an inspection. Got to be worth it I think.
Thanks everyone

Structural engineer bought and paid for, going in next week hopefully. so If it is subsidence, do we ask for the cost off of the asking price, or will it always be bad for future buyers. I would feel quite comforted by a underpinned house, but I doubt everyone would....

It wouldn’t worry me too much and like you a previously underpinned house would be reassuring

Not to say that’s the same for everyone though

If there is subsidence and you re negotiate the price, you don’t want to just look for the cost of repair to be covered, rightly or wrongly, the house also has a lower value, an underpinned house has a lower value than one that’s not been underpinned.
I live on clay in Essex and you do see a reasonable amount of subsidence but I would avoid buying a previously underpinned house, it knocks maybe 1/3 off the value IMO.