Natural Subsidence - Moderate rating

[Lin & Roger]

Dear Forum

Although there were no obvious sign of any cracks or subsidence when we viewed a house and the mortgage surveyor did not see any nor a friend surveyor. However, the Environmental Report indicates that there is a moderate natural subsidence potential in the area surveyed (250meter radius). There were some subsidence for a block of flat which is over 600 meter away. There were several houses sold last year and this year on the same road as the house we are hoping to buy. Can any one please tell us how worry we should be when the report say "moderate natural subsidence potential for natural ground instability-shrinking/swelling clay ground- buffer zone 0-50 m

Thanks ,

 

[noseall]

clay substrate is particularly sensitive to extremes of wet weather, followed by extremes of dry weather.

it expands and contracts accordingly, and can be rather troublesome to a rigid building.

clay heave is also a problem. this can occur when an area of parched clay has been built upon, (usually due to a nearby tree sucking the ground dry) then there is a wet spell, and hey presto the floors start rising or heaving!

 

[Lin & Roger]

clay substrate is particularly sensitive to extremes of wet weather, followed by extremes of dry weather.

it expands and contracts accordingly, and can be rather troublesome to a rigid building.

clay heave is also a problem. this can occur when an area of parched clay has been built upon, (usually due to a nearby tree sucking the ground dry) then there is a wet spell, and hey presto the floors start rising or heaving!

THANKS for your reply. The house we hope to buy has a big oak tree at the end of the garden (120 feet) and 10 meters away to the front of the house there is an island of trees. The road is a conservation area. Am I right to say that this house may have a bigger problem with clay heave than if there were no oak tree or other trees surrounding it?

 

[Static]

With the tree that close its shrinkage is the main worry. Tree sucks up moisture in the soil around the foundations. How old is the house?

 

[Lin & Roger]

With the tree that close its shrinkage is the main worry. Tree sucks up moisture in the soil around the foundations. How old is the house?

Thanks Static for your reply. The house was built in 1930'

L&R

 

[Lin & Roger]

clay substrate is particularly sensitive to extremes of wet weather, followed by extremes of dry weather.

it expands and contracts accordingly, and can be rather troublesome to a rigid building.

clay heave is also a problem. this can occur when an area of parched clay has been built upon, (usually due to a nearby tree sucking the ground dry) then there is a wet spell, and hey presto the floors start rising or heaving!

Hi Noseall, how do I find out whehter the soil is clay sustrate/heave? Please advise - thanks again

 

[noseall]

only by digging a hole, or see if you can glean some info from neighbours.

you will probably ned to dig down 450-600mm.