Advice: Extending a house over drains; subsidence near trees
Discussion
Hello forum!
looking for advice from PH hive mind...
We're after the next step house, have been for ages. Recently, a house has come up that we're really interested about, but also really scared about..
House as it is:
Total house c. 2300 sq ft, but 300 sq ft is a single story extension.
Single story side extension is subsiding. Engineers report says due to the "f
k off massive tree" that's c. 4m away but also under TPO. When I say massive, it's >5 stories height, judging from street view.
Conclusion of engineers report in selling pack: Underpinning / piling, but more economical to rebuild.
Meanwhile, a mate of mine tells me not so simple (can't dig a trench in root zone, can't risk lie of tree, he gave up on application).
Plot is wonderful; totally ticks the "location, location", massive, established walled garden, most of which is sadly TPO'd but the kids would have meters of "den" to play with.
To make house what we want, would need 2 stories extension rebuild on footprint of side extension, plus c. 3m single story across the whole back of house inc extension. Main drain runs parallel c. 2.5m - 3m away from back of house. More fun.
Naturally, with all of this, the house is going well under local market rate for similar houses. We could theoretically buy with no mortgage, by taking current house value plus all savings. Would need to remortgage to do the extensions. I think the struggle to mortgage a subsiding building is also how it's the price it is.
So - PH massive...
How much of a ballache is build over sewer?
How much of a ballache is building with piling in root area of a TPO'd massive tree?
Can you tell me if this is madness or genius?
Thanks in advane!
looking for advice from PH hive mind...
We're after the next step house, have been for ages. Recently, a house has come up that we're really interested about, but also really scared about..
House as it is:
Total house c. 2300 sq ft, but 300 sq ft is a single story extension.
Single story side extension is subsiding. Engineers report says due to the "f
k off massive tree" that's c. 4m away but also under TPO. When I say massive, it's >5 stories height, judging from street view. Conclusion of engineers report in selling pack: Underpinning / piling, but more economical to rebuild.
Meanwhile, a mate of mine tells me not so simple (can't dig a trench in root zone, can't risk lie of tree, he gave up on application).
Plot is wonderful; totally ticks the "location, location", massive, established walled garden, most of which is sadly TPO'd but the kids would have meters of "den" to play with.
To make house what we want, would need 2 stories extension rebuild on footprint of side extension, plus c. 3m single story across the whole back of house inc extension. Main drain runs parallel c. 2.5m - 3m away from back of house. More fun.
Naturally, with all of this, the house is going well under local market rate for similar houses. We could theoretically buy with no mortgage, by taking current house value plus all savings. Would need to remortgage to do the extensions. I think the struggle to mortgage a subsiding building is also how it's the price it is.
So - PH massive...
How much of a ballache is build over sewer?
How much of a ballache is building with piling in root area of a TPO'd massive tree?
Can you tell me if this is madness or genius?
Thanks in advane!
well there are plenty of other houses to buy
if you really want it
make a TPO application for felling, use the engineer’s report i trust he has done some level monitoring to show the movement is seasonal and downward he may need to to persuade the LPA the tree is the cause of the damage
crack monitoring doesn’t tell the full story
the building is founded on a cohesive soil?
Movement should be recovering or recovered now and beginning a downward movement by late spring as leaves come into maturity progressin through the summer
It could be differential settlement due to the extension and the house being founded at different depths and movement at different rates??
What about the vendor, have they made a claim for subsidence with their buildings insurers and what was the outcome?
If the tpo app fails you can appeal but it isn’t quick
Tpo – 8 weeks determination
Appeal fk knows probably 35 weeks +
perhaps see above - buy another house
if you really want it
make a TPO application for felling, use the engineer’s report i trust he has done some level monitoring to show the movement is seasonal and downward he may need to to persuade the LPA the tree is the cause of the damage
crack monitoring doesn’t tell the full story
the building is founded on a cohesive soil?
Movement should be recovering or recovered now and beginning a downward movement by late spring as leaves come into maturity progressin through the summer
It could be differential settlement due to the extension and the house being founded at different depths and movement at different rates??
What about the vendor, have they made a claim for subsidence with their buildings insurers and what was the outcome?
If the tpo app fails you can appeal but it isn’t quick
Tpo – 8 weeks determination
Appeal f
k knows probably 35 weeks +perhaps see above - buy another house
Relativley simple to remove the existing extension, leaving its foundation in place, then install mini piles within the existing footprint. This should be acceptable to the tree officer. A raft foundation can then be installed to support the new extension cantilevering over the old foundation.
This avoids having to declare underpinning work to insurers or any future buyers.
This avoids having to declare underpinning work to insurers or any future buyers.
None of it is difficult, mini piling is the easiest solution. Water authority will ok a piled solution, piles will not affect the root zone and heave precautions to the piles and beams of the new foundations will sort out any potential clay heave or root influence to the build.
If you need an engineer to design founds and a company to price for the proposal just let me know. Over 20 years experience in this type of work (underpinning and mini piling).
If you need an engineer to design founds and a company to price for the proposal just let me know. Over 20 years experience in this type of work (underpinning and mini piling).
Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff