House with minor subsidence

Davesnave

cecoo wrote: »

Hi, apparently the builders ran the water from the flat roof extension into the garden and the ground was soaked. They had CCTV etc and have now connected them to a drain round the side/near the front of the house that takes the water from the dishwasher and washing machine. They’ve supplied photos of the drain work showing how water logged the ground was around the extension. However, the final Certificate of Structural Adequacy says the cause is clay shrinkage as a result of the Oak tree in the neighbours garden...

Yes, there's a contradiction there; the ground being too wet, and then again, too dry. I'm not saying that couldn't happen, as clearly it could in a year of extremes. The problem is, no one took account of the ground conditions when planning the extension's foundations.

If the builders put surface water drains into the sewer system then they broke the regulations, but they may have done that with tacit approval from a building inspector. I've done similarly myself and had the work signed-off, because the inspector knew a soakaway would be unsatisfactory.

The trouble is, if everyone does that, people downstream are more likely to be flooded.

cecoo

Davesnave wrote: »

Yes, there's a contradiction there; the ground being too wet, and then again, too dry. I'm not saying that couldn't happen, as clearly it could in a year of extremes. The problem is, no one took account of the ground conditions when planning the extension's foundations.

If the builders put surface water drains into the sewer system then they broke the regulations, but they may have done that with tacit approval from a building inspector. I've done similarly myself and had the work signed-off, because the inspector knew a soakaway would be unsatisfactory.

The trouble is, if everyone does that, people downstream are more likely to be flooded.

Thank you! The extension was done in the 70s so not sure what the building regs were. The seller says she thinks they rushed the job at the end so the drains were a botch job at the end. It might be worth mentioning a friend in the same house up the road said their flat roof extension has very shallow foundations and in order to extend a bedroom over the top they had to reinforce them.

Are you a builder? Do you think this all sounds suspect and could be a big problem? We really want someone to be able to say either it’s fixed and tree is unlikely to cause more problems or steer clear because some recent movement may only be the start of more to come... We’re trying to make a sensible decision but it’s swayed by the fact we really want it...

Tom99

cecoo wrote: »

In the Certificate of Structural Adequacy, the oak tree is listed as the cause of movement due to clay soil shrinkage - and not the drains.
We can’t get insurance with the seller’s current insurer (big brand) but have found insurance with a specialist insurer, meaning a higher premium and £2,500 subsidence excess.

Has the new insurer seen the Certificate of Structural Adequacy and aware that nothing has been done to the oak tree?
Was the recommendation to fell the oak tree or just reduced it?
I doubt a structural engineer is going to give you the black and white answer you would like.
It may come down to just taking a risk providing you are sure you can insure against further damage with a £2,500 excess.

Bluebonnie

There’s a bit of a contradiction here. The damage could have been caused either by subsidence or heave. Subsidence if the oak tree was taking all the water out of the ground, heave if the builders bodge job was causing ground to become waterlogged.

Do you know the dates of (1) construction of the extension, & (2) when the flat roof water was taken away as it should have been in the first place? If the “subsidence” claim was only made within the last two years, how does this relate to (2)? Was the claim a year or two later, or more?

This the trouble with structures built on clay - a permanent nuisance, and not much fun for gardening.

Davesnave

Bluebonnie wrote: »

This the trouble with structures built on clay - a permanent nuisance, and not much fun for gardening.

The entire London Basin is built on it. I blame the Romans!

cecoo

Bluebonnie wrote: »

There’s a bit of a contradiction here. The damage could have been caused either by subsidence or heave. Subsidence if the oak tree was taking all the water out of the ground, heave if the builders bodge job was causing ground to become waterlogged.

Do you know the dates of (1) construction of the extension, & (2) when the flat roof water was taken away as it should have been in the first place? If the “subsidence” claim was only made within the last two years, how does this relate to (2)? Was the claim a year or two later, or more?

This the trouble with structures built on clay - a permanent nuisance, and not much fun for gardening.

The house was built in the 60s and I think the extension was 70s or 80s - so pretty old. Subsidence cracks were discovered a couple of years ago when they tried to sell and so all the monitoring and drains were fixed after that - so very recently.

cecoo

Tom99 wrote: »

Has the new insurer seen the Certificate of Structural Adequacy and aware that nothing has been done to the oak tree?
Was the recommendation to fell the oak tree or just reduced it?
I doubt a structural engineer is going to give you the black and white answer you would like.
It may come down to just taking a risk providing you are sure you can insure against further damage with a £2,500 excess.

I’ve shared all the information with the new insurer so they have all the facts and know about the remaining tree. The recommendation was to remove the tree. It might also be possible we can keep the existing insurer on, been a bit of a mission to speak to the right person as it’s not our house and our policy but I’m hoping we can keep them on for consistency.

coporalcuddles

cecoo said:

Tom99 wrote: »

Has the new insurer seen the Certificate of Structural Adequacy and aware that nothing has been done to the oak tree?
Was the recommendation to fell the oak tree or just reduced it?
I doubt a structural engineer is going to give you the black and white answer you would like.
It may come down to just taking a risk providing you are sure you can insure against further damage with a £2,500 excess.

I’ve shared all the information with the new insurer so they have all the facts and know about the remaining tree. The recommendation was to remove the tree. It might also be possible we can keep the existing insurer on, been a bit of a mission to speak to the right person as it’s not our house and our policy but I’m hoping we can keep them on for consistency.

I have a very similar issue but the problem I have is the seller’s insurer is saga and they say they won’t insure me because I’m not 50 yet ! How do you get over that ?

The certificate of adequacy will be issued soon. I am told that the repair bill or payout from the insurance claim is £8,000, which the vendor will use to fix the cracks. No foundation underpinning is required. In our case the tree is a substantial Silver Birch in the pavement fronting the building which is Council managed.

How does one determine the diminution in value of the property, 5%, 10% , 20% of such a claim and subsidence issue.  As the tree is now being managed by the council the problem could reappear.  Is there some formula or rule that you can use to work out the reduction in asking price of said such a property ?