Moderate-high risk of subsidence in a new build

Elsie89

I've reserved a new build property and have received our searches in preparation for exchange of contracts. 

Our groundsure report has put us in a 'moderate-high risk of subsidence'. I think this is from the compressible ground risk as it is built predominantly on clay and a sloped area. 
I've found the geological engineer report who has essentially made recommendations on foundations based on the soil analysis. 

I'm still extremely nervous about purchasing a house with this risk of subsidence. I am a first-time buyer so haven't been through this process before. I've very concerned that if subsidence did occur then it would greatly affect the value of the property. 

What I've done so far

Contacted my solicitor who have essentially reassured me that the ground stability has been taken into consideration during the build process
Contacted my local authority to see if any reports of any other local properties with subsidence
Contacted the NHBC to understand what would happen should any subsidence occur

Should I be completely put off by this report? Or is it reasonable to assume that new builds will have mitigated most of the risk with their foundations?

THank you in advance

user1977

Elsie89 said:

is it reasonable to assume that new builds will have mitigated most of the risk with their foundations?

Yes, and probably far better than any older property would have.

Also bear in mind that the ground conditions are likely to be much the same in the whole neighbourhood - so where are you going to buy if not this house?

eddddy

Just to be pedantic - the report isn't saying that the house you are buying has a moderate-high risk of subsidence.


The report is saying that, in general, the soil in the area presents a moderate-high risk of subsidence.


The builders will have got that information long before they started building - plus they would have dug trial-holes, tested the soil, analysed soil samples etc.

Then their engineers would have designed foundations suitable for that kind of soil - to prevent subsidence.


The 'science' of designing foundations today, is more sophisticated and more rigourous than the 'science' was, say, 40, 50, 60 or more years ago. So a new house should be less prone to subsidence than an older one.


But it's still possible that the 'science' isn't perfect, or that the builders were sloppy in doing their tests - so the risk isn't zero. But the risk should be very small.




FWIW, as an example, I watched a developer dig 20m deep piles (a type of foundation) for a new bungalow on soft clay ground, surrounded by trees. Presumably, because the engineers said that was necessary to make sure the bungalow didn't subside.

(You could say the bungalow was a bit like an iceberg - the foundations underground were deeper than the height of the building.)

All the older houses around the bungalow almost certainly have much shallower foundations.

 

arrows123

Just to add a bit of info from another side, I moved into a 6 year old house, as a FTB, it had an oak tree on neighbouring land but about 8 metres away. Over the next 18months a large crack appeared in the corner of the one window. As it was still covered by the NHBC certificate, they came out and diagnosed subisdence and paid for underpinning to be done. During their investigations they ascertained that the foundations had not been done correctly and to the correct depth to take into account the Oak tree. The underpinning rectified this. I'd want some sort of documentation to prove the developers have recognised the subsidence risk and what they have done during the build to mitigate the ground.