Subsidence

[annabannan]

Has anyone had any experience of subsidence caused by a neighbours tree?

Yes, sort of.

We bought a house knowing its front bay had had some sinking and cracking. The sellers disclosed an old engineer’s report saying it was probably caused by a goat willow in neighbouring front garden.

We wrote to the owners of the next door house and said we would like the tree to be removed or we’d expect them to pay for any further repairs needed. Slightly to our surprise they agreed and took it out.

We were lucky in that it was a weed tree (self sown) and the house was owned by a company rather than an individual so perhaps more likely to just sort the issue rather than argue.

The problem is removing a tree can cause subsidence issues too. The tree controls the water content of the soil around it especially if it is a large tree and particularly if you are in clay soils which are pretty common in the UK. If the tree is large like an old Oak or Beech tree, and you remove the tree which has be drawing very high amounts of water from the soil that affects the strength of the soil too.

Im totally in the hands of the insurance company but causing me so much stress. I think the tree is a purple leaf blossom.

That sounds like a pain @annabannan what are the insurance company doing? Is the subsidence very serious?

Sending a surveyor round to confirm if subsidence which they are sure it is from my photos and video and then need to find the cause which the are confident is the neighbours tree but are saying it could take up to 2 years to rectify.. that's what's causing the stress!

@Alleycatz I thought the issue that removing a tree causes was the opposite of subsidence aka heave...this is where the ground increases its water content and expands. Still causes problems though

Yes I remember worrying that removing the tree could cause heave. However in our case it certainly hasn’t. Possibly because it was heavily chopped back a few years before it was removed (I imagine chopped back when our neighbours complained and then removed when we did) - so its water demand reduced in stages iyswim.

I really don't know, like I said I'm being led by the insurance company, just want it sorted asap, but have a feeling it's going to be a long drawn out process

Yes heave.

We have subsidence issues in our house that we have lived in for the last 10 years @annabannan caused by a drainage issue that we haven’t yet bothered to rectify because the house needed a lot of work and other aspects were a priority.

Don’t get me wrong subsidence can be very serious but equally it can be not particularly serious like ours. We are both structural engineers in a former life and not worried about our situation for example. If yours is a more serious issue they can prop walls temporarily as a stop gap. If the surveyor picks it up as being serious they will advise a course of action.

@alley thank you, I'm hoping it just our conservatory that's affected but only the surveyor will confirm that, preparing myself for a long drawn out process so will be selling all the furniture in there as no where to store it

@annabannan Your conservatory probably has no foundations to speak of. It’s probably on a concrete slab that is not up to withstanding ground movement. If it’s not the main house, it’s not worth worrying too much.

If you want to dig down by the side of the conservatory, you can see what foundations it’s got. Probably hasn't. Hence the issue.

God knows what a “purple leaf blossom” tree is! I would get a better identification than that. You can also do your own survey for subsidence. Are windows and door frames not quite right? Have they moved? Are doors sticking? Are there bricks with cracks? Is brickwork looking out of kilter? Are there cracks in mortar? Look at a reliable web site for pictures.

This could be caused by a leaky drain washing away soil under the conservatory. It could be a poorly made concrete raft. How is the conservatory built? Is it expensive or cheap? If it’s built on a shallow raft, the tree probably isn’t to blame. It’s possibly cheap construction. Is it pulling away from the house?

2 years is excessive but not if they monitor it first. This is to check for ongoing movement, or lack of it.

Don’t you have big yellow storage or similar near you?

OP are you able to share the pics of the subsidence?

Sounds like the tree was there before the conservatory was built?

We have a 10 year old conservatory building (oak framed) around 5m from a mature oak tree in our own garden. We have 2m deep foundations for the conservatory. All buildings need to be designed on suitable foundations for soil type and trees. You don’t have to worry about trees with a new building of foundation design takes everything it should into account.

Subsidence is far more common in older buildings when no trees were near when they were built. Or no one realised the implication of trees growing. A conservatory is almost certainly fairly new but most contractors don’t design foundations for them as they should. They are frequently not treated as a house and no building reg control to speak of. So they are vulnerable. The tree in this case has no name, no size and we don’t know distance from house. It’s telling that the conservatory has the issues though.

Should read: if foundation design takes everything into account.