Could this be subsidence?

[housebuyingistheworst]

I had a full building survey done on a property and it indicated signs of structural movement. This refers to one horizontal crack in the foundations (photos attached). However, the surveyor refuses to say if it's subsidence ('it could be'). A structural engineer would say something similar without digging up the foundations. To make matters worse, there's a giant buddleia plant right in front of this crack, which could be the culprit.

Those who have experienced cracks /subsidence/ buddleias - what do you think? There are no internal cracks in the house or other signs of subsidence, but I'm worried. Would you go ahead with the purchase given this uncertainty? Your views would be much appreciated as I'm at a loss

Just to be clear as terms have been used by posters that are not correct. Heave is where the soil expands because there is too much moisture in it. Eg from a burst pipe, from waterlogged soil where trees have been cut down and the water they would have drunk remains in the soil. This typically pushes walls outwards and gaps can appear between ceilings and walls. Heave is expansion of the soil around the house and pushes the walls upwards and outwards.

Subsidence is where the soil surrounding the foundations is too dry. The foundations and the weight of the house subside by compressing the desiccated soil.

Both can be corrected. Those cracks may be neither. Just poor maintenance but you would need to know for sure and surveyors never say one way or another because they are not really qualified to do so. They won’t take the risk of an incorrect diagnosis. Loss adjusters argue about the size of a claim but are rarely qualified structural engineers. So: you need a qualified structural engineers report. Yes, they will monitor the cracks. Yes they will want to look at foundations. An experienced one might even look and tell you immediately what the problem is. Or that there isn’t a problem at all! Only then will you easily get insurance.

Underpinned houses are very safe purchases! The work has been done!

The insurance company wants to see the survey. I'm now seriously considering letting this house go

When you say foundations is this what you mean? The pictures appear to be above ground level and show render. Rather thick render. Is the whole house rendered? Are there any other cracks? Wonky window frames? Cracks in bricks in that area? If you like the house, you could get a Structural Engineer to do an assessment. However my inclination would be to walk away if insurance is going to be difficult. The insurance company probably won’t insure it without a structural engineers report giving it a clean bill of health. If it’s got problems the vendor should probably sort out the claim on their insurance.

The current insurers are not officially obliged to give you cover, but likely they will due to a market gentleman's agreement. There are specialist companies who will offer cover but with an ongoing subsidence issue, they would usually refer back to current insurer or potentially offer cover excluding subsidence - I'm an insurance underwriter and I specialise in properties with subsidence issues.

Agree with pp that fully underpinned houses are usually better than non underpinned ones, but partially underpinned houses can be an issue due to differential foundations. The upheaval might be quite an issue for you though, and if you don't get a serious reduction I'd walk away.

@ToothlessIsMySpiritAnimal, thanks for explaining this. We'll see what the insurers say after reading the relevant bits of our survey.

Which part of the country are you in? Around our way (London clay) its hard to find a house which isn't underpinned and typically insurance is passed on with the house as continuous insurance. If it is subsidence current insurers will be liable to pay out and they generally have an interest in retaining the policy.

If you are in an area of high soil shinkage there you can also take the view that a house which has already been underpinned is a safer bet than one which hasn't.

Get a local SE if you can and talk to them on the phone after the visit rather than just reading the report.

@C8H10N4O2, yes I'm in London.