UKTC Archive

Re: Subsidence where foundations less than 300mm deep

Subject: Re: Subsidence where foundations less than 300mm deep
From: Wayne Tyson
Date: Sep 07 2020 20:57:25
Pardon the density of my gray matter, but I continue to fail to see why
trees are blamed for subsidence. Perhaps I haven't been paying attention,
but is this cited anywhere in the US? Are there scientific studies
demonstrating the fact? I understand the "theory," but question the
conclusion.

The engineers I know would use pilings instead of foundations. Then there's
the famous Frank-Lloyd Wright-designed hotel in Japan.

Would anyone care to lead me out of the darkness?

Wayne

On Mon, Sep 7, 2020 at 5:15 AM Jon Heuch <jh@xxxxxxxx.co.uk> wrote:

Trevor



There is nothing magic/noteworthy about 300 mm deep foundations.



What I expect they are trying to say is that seasonal movement in a
property
should be less the deeper the foundations. With shallow foundations some
seasonal movement can be expected & identifying the cause of that movement
with shallow foundations can sometimes be problematic.



a.      Would the same or similar movement have occurred without the trees?
b.      Will removal of the trees solve the problem i.e. reduce the
seasonal
movement to within acceptable limits?



"no other cause produces a similar pattern"....well I wouldn't state this
definitely related to a 300 mm foundation. It depends what the structure is
so a light weight structure such as a garage might move seasonally on a
500mm foundation without any trees..whether that is a problem or not
depends
upon the structure and whether it can put up with the differential
movement.




Jon






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