Buying house deemed as high risk for subsidence

Olistanding

Hi

I am in the process of buying a period house in dulwich (se london). 

We found out after initial enqueries the house had been underpinned 21 years ago after some subsidence with a central wall in the middle of the house.

About 5 years ago the house was extended and the wall that was underpinned was removed and the extension was fitted with deeper foundations.

I had read that the house would be more secure than a non under pinned house however given the wall that was underpinned was removed the previous underpinning apparently doesnt have any impact.

Our surveyor has advised that there are cracks to some of the walls these appear to be the result of normal seasonal movement rathsr than anything they are currently concerned about.

 However, they said it is at high risk of future subsidence due to:

- the previous issue

- being an end of terrace

- the house having shallow foundations other than the extension

- being on london clay

- having two trees close by that are outside of the boundaries of the property (one a few metres away on the pavement and anotjer in a neighbours rear garden)

We are considering whether to pull out but really like the area and house and other properties in the area may well have similar levels of risk.

Mainly concerned about the prospect of losing money on it should the subsidence re occur given so many places online talk about significant reductions in house prices with subsidence and its quite possible we would want to move after 5 years for more space 

Just wondering what other peoples attitudes to such issues are and whether you would be likely to buy a house with a high risk of subsidence?

Thanks

gwynlas

It is a period house meaning that its stood for many years despite having shallow foundations. The extension built on deeper foundations is presumably deemed safe. All houses in surrounding streets built on London clay and presumably at the same time have shallow foundations and bear the same risk. Why should the house be hit by subsidence during your ownership?

Olistanding

Thanks for this. Yes my assumption was that all houses in the area would be at a similar level of risk however the surveyor has advised this house is specifically at a greater level of risk due to the proximity of two trees which are on the public pavement and neighbours rear garden making it difficult to cut them back. He has also said the fact it has previously had subsidence makes it higher risk even though this was some time ago.

mark_cycling00

Surveyors always highlight the worse case scenarios partly because they'd be liable if they gave assurances on something that they couldn't confirm 100%. (Or failed to mention a possibility)

You'd expect that the last few years of extreme weather would have brought forward subsidence problems. So you'd see more than small seasonal related cracks from the moisture levels in plaster.

There are some trees that can grow rather long, big roots - I think poplars are one, but most trees in London are London planes and follow normal root patterns. 

It doesn't sound like you should walk away at all. It's just very scary reading these things when you're about to spend a huge amount of money.

His terms "higher risk" is relative, it might be just 1% more. No he won't give you a percentage because he might become liable for that assessment 

Bigphil1474

Maybe speak to your current insurers and see what they say about insurance cost estimate on the new property? Or just do a comparison site search. If the premium is going to be extortionate then that probably tells you all you need to know, if it's reasonable, at least you'll have the comfort of knowing your covered if the worst happens. 

tooldle

An underpin (normally) means a raft of poured concrete. How extensive was the work? 

Olistanding

It was a beam that was fitted under an internal wall although that wall has since been removed. Presumably it still serves some purpose in strengthening foundations but isn't under any structural wall

alanyau88

I would declare it to the insurance comparison portals and see the difference between underpinned and not underpinned.  Anything above £500 in my opinion would probably not be worth it given that this quote may rise yearly.

I pulled out on a purchase where the house was flooded twice before.  The insurance companies were not happy and flood re aren't going to last forever.  Consider buyers in the future, would they be put off by the subsidence issue?  Ultimately it's your choice.

mark_cycling00

Just a thought.

If you mention your concern to the seller they'll have one of two reactions:
1. Argh darn it! They've discovered the terrible subsidence risk
2. Oh no they're getting worried about something that's been absolutely fine 

You could ask about their current insurance situation. That's what we did when house had a quite recent but small subsidence claim. 

Our seller was very happy to tell us the premium, excess on subsidence claims and who their insurer was. 

Comparison sites aren't great at complex scenarios so you might get unrealistic results.

tooldle

Have a chat with the surveyor. London clay is a risk but, so many many houses are built on areas of London clay. Clay expands and contracts with climate conditions. The trees (depending on size) will potentially taking up large volumes of water and this may cause some additional shrinkage. In wet conditions the trees might be seen as a bonus.
It comes down to balance. An underpin 21 years ago with no issues in the intervening period. The alternative to find a property that isn’t built on clay, and that is quite a task if you are in the South.

Olistanding

tooldle said:

Have a chat with the surveyor. London clay is a risk but, so many many houses are built on areas of London clay. Clay expands and contracts with climate conditions. The trees (depending on size) will potentially taking up large volumes of water and this may cause some additional shrinkage. In wet conditions the trees might be seen as a bonus.
It comes down to balance. An underpin 21 years ago with no issues in the intervening period. The alternative to find a property that isn’t built on clay, and that is quite a task if you are in the South.

Thanks for this.

I did have a chat with the surveyor and he was pretty clear in the point that the property was at a greater risk of subsidence than others in the area. His main rational to this seemed to be the presence of trees close to the property that were on public land and the neighbours land, and the fact it had previously suffered from subsidence. However, I can't find much evidence that previous issue with subsidence a long time ago makes it more likely to happen again and many other properties in the area have trees nearby.  Think I night try and get a second opinion. Other reasons he mentioned were the soil type and shallow foundations but that's the same for most houses in the area.

I guess the other thing is whether we think the stigma around it having had subsidence in the past is likely to impact on what we can sell it for regardless of whether its a continuing issue