Historic subsidence

[Bluebaron]

Looking at a house and just got the legal pack.

 

I’ve found a report of subsidence in 2013/14. It’s all been fixed and was blamed on clay soil and three large oak trees less than 10m form the house.

 

the report recommended removal of these trees and this hasn’t happened. 10 years later I’m concerned that a re-occurrence is a distinct possibility.

 

I’ve asked the seller to confirm and why the trees have not been removed. Should I walk away from this one or what would you recommend?

[Jilly]

Who owns the trees? 

[Jilly]

You need specialist advice.

 

Sometimes crown reduction is advised instead, to prevent heave which could happen if the trees were removed, due to the sudden extra water under the house, so they may have got another opinion?

Could it be in a Conservation Area and the trees have TPO's?

Or they don't own the trees? 

Removing the trees might ruin the character of the house/area?

Lots of houses have been underpinned, it's not the end of the world, but it scares people and lenders. 

 

If you proceed, you must stay with the same insurance company, the policy can be transferred and you must confirm this will be the case as part of your due diligence. Other insurance companies won't touch it. 

[Gus Potter]

Cracking insight from Jilly here.. so much info in seven lines of text..

 

Folks read every line of Jilly's text,  learn and digest the deep knowledge she is imparting. To get the best out of this you'll need to go and do your own work.. Jilly is saying.. here is where you need to look out for your own benefit.

 

Just a quicky for any doubters here.. Jilly talks about underpinning.. she has been there and worn the tee shirt in terms of piling etc on her domestic project.. she knows her stuff.

 

Or bluntly.. if you don't take her advice then don't come back on BH complaining later if it goes wrong.

Edited May 5 by Gus Potter

[Bluebaron]

Thanks Jilly,

 

yes the trees are all on the property. They currently are not TPO’ed.

I was concerned about heave, I’ve asked if a heave survey was carried out.

 

I’m waiting to hear back. It doesn’t look like any crown reduction as taken place in the last 10 years. Except from 2014 report below.

 

not sure what advice to get here? Full structural survey? Would this include test pits to assess root invasions?

the next door had just had a small rear extension added and the builder said there were roots everywhere he got away with 2.5m trench fill. He’s further from the trees, he said piling would have been a better option but homeowner wanted to save money.
 

I was hoping to remove the trees anyway to use the side plot for a new dwelling. I’ve read up on heave and not sure how to prevent it causing damage to existing particularly with the history.

 

 

 

 

[twice round the block]

Could make for a very expensive project.

It's the unknown factor.

Specialist tree surveys by a company who knows what there talking about could be of some help, but it's not guaranteed. 

 

 

[JohnMo]

I assume the trees would need permission to be altered or removed, it's also gamble the council may say NO!

 

Plenty of other houses with less hidden surprises, just move on to the next one.

[Jilly]

12 hours ago, Gus Potter said:

Cracking insight from Jilly here.. so much info in seven lines of text..

 

Folks read every line of Jilly's text,  learn and digest the deep knowledge she is imparting. To get the best out of this you'll need to go and do your own work.. Jilly is saying.. here is where you need to look out for your own benefit.

 

Just a quicky for any doubters here.. Jilly talks about underpinning.. she has been there and worn the tee shirt in terms of piling etc on her domestic project.. she knows her stuff.

 

Or bluntly.. if you don't take her advice then don't come back on BH complaining later if it goes wrong.

Thank you Gus, but of course, you taught me nearly everything I know about the subject 😊

[Jilly]

You could just assume you need piled foundations and work from there. Quotes can vary wildly, by many £1000s

[saveasteading]

Great advice above.

It's a shame for the current owners but it is their problem at the moment.

Once you buy it, it is your problem and cost, plus at any future sale the potential buyers will be asking these same questions and wanting a bargain or walking away, or not getting a mortgage.

The magic distance for oaks in clay is 28m, so it could be the whole building needs underpinning. 

Reducing the crowns troubles me as a suggestion. Trees grow again.

 

You need an SE to confirm the above, and then to get a costing.  I used to quote for underpinning at many £100 per metre. 

After you've spent that money and had the disruption  you have a house with increased insurance premiums with little choice or competition.

 

OR:  I don't know if this is a real and current problem or more a concern. Are there cracks?

 

So:

 

Buy it for a bargain and don't underpin. 

Live with it.

you save the £30k or whatever in case you need it later.

 

A wild thought more for discussion than as advice. Maybe watering the garden will stop the clay shrinking in the summer. Divert all your rainwater that direction, into French drains. There's only so much water the oaks can drink.

[Bluebaron]

🤔 thanks for advice, I’ll wait and see what comes back. At the moment I’m paying market value, if anything a slight premium! 
 

no cracks at the moment so assume the 2013/14 repair was successful. If I build/extend it will certainly be piles due any heave risk. 
 

either way the trees will come out. They are on the land with no TPO so I’m assuming I’ll just get it done asap before anyone can complain etc.

I think I’ll probably go back and say I want the trees removed entirely before completion and a full foundation survey done at their cost. If not I’ll have to drop price significantly. 

 

[saveasteading]

5 hours ago, Bluebaron said:

If I build/extend it will certainly be piles due any heave risk. 

Make no  assumptions. Ground moves seasonally, trees or not. It might not be best to sit an extension on piles while the rest continues to move. Needs SE advice come the time.

 

5 hours ago, Bluebaron said:

either way the trees will come out.

 

Why? If the building has been given deeper foundations appropriate to the trees, then it is sorted.

Trees are good.

When you remove a tree the clay ground will adjust to the new wetter conditions , and may rise.

 

On 04/05/2024 at 20:54, Bluebaron said:

10 years later I’m concerned

We have had several exceptionally hut and dry summers, so 10 years seems to be  a good test.

[Bluebaron]

Trees have to come out as I’m planning a new build in the plot. 

[saveasteading]

53 minutes ago, Bluebaron said:

Trees have to come out as I’m planning a new build in the plot. 

OK.

If you said that then I missed it. That's different.

Get professional site specific advice.

[twice round the block]

On 05/05/2024 at 18:27, Bluebaron said:

 

I think I’ll probably go back and say I want the trees removed entirely before completion and a full foundation survey done at their cost. If not I’ll have to drop price significantly. 

 

I'm not sure any seller would agree to that.

 

It's down to you to get a full survey done, then take a punt on it if you think it's still viable.

To remove large oaks with a climber and ground team is probably £800 per tree, without stump grinding.

Edited May 6 by twice round the block

[ProDave]

Add some more £££££ for dealing with those electricity cables.

[Bluebaron]

£800 would be great last time I had a tree down cost me £2500 and this is a lot larger. 🤷🏻‍♂️ 

 

These are the tree la I’m looking at. Not sure what that photo above is. 

[Bluebaron]

OK so i'm still debating on this one.

 

 

Pro's, 

 

established residential area

guy across the road has done similar

end of cul-de-sac location

Looks like a good shot at getting PP. (local history)

If not ill go down the side extension route

 

con's

history of subsidence. Looks to fine now but the 3 large oaks 7-10m from the house right where i want to build. 

If i take the trees out there's a real risk of heave, this shouldn't effect the new build as ill design around the risk. But it could affect the existing including the neighbour. (who just finished a rear extension)

 

Aso taking out 3 large oak tree will piss a few locals off i bet as to be fair they are quite nice trees that predate the house (1950). 

 

Spoke to one SE who said i would mad to remove the trees and would definitely cause a heave risk. (over the phone didn't see site).

A second specialist soil guy told me to test the soil to see the clay content. I'm thinking i could get a soil survey/heave assessment done to start but will probably be an educated guess. 

 

Thoughts?

 

It is worth the investment in surveys/cost/time or is this gamble a bit high risk?

 

If is wasn't for the trees i would be all over it.

[saveasteading]

Leave the trees, get site survey, design any new foundations accordingly, probably over 2m deep.

 

 

 

[Bluebaron]

I would but sadly can’t build a house on top of a 50’ oak tree!

[saveasteading]

55 minutes ago, Bluebaron said:

on top of a 50’ oak tree!

Didn't you say they are 7m away?

 

Anyway I've changed my mind. The trees would overshadow the house and become misshapen. The pragmatic solution is to let the trees be, but divert rsinwater to them, and don't build here at all.

[Bluebaron]

Well the point I’m getting at is I’m looking at the plot as a potential site for a self build. The trees are 7-10m from the existing house and would be in the way of any development.

removing the trees may pose a risk to the existing property.

 

so I’m wondering if it’s worth the punt to secure a potential plot or whether to walk away before I spend a fortune of expensive surveys.