I'm not a specialist in subs, but over the years I've done quite a few. In
all that tine I have dealt with just two genuine heave cases - and they went
to court. Jon is absolutely right in that the whole subject is mystery. We
may understand the principles but every case is different in one or more
ways, usually the latter.
Tree-related subs is usually to do with differential soil movement,
aggravated by variations in foundation type. "My" heave cases seemed to
affect the entire building, and had the classic non-tapering cracks, and one
had floorboards which had pulled out from under the skirting boards. Rather
than causing repairable damage, both buildings were in effect write-offs.
I can't say that my contributions as an arb were sparkling, but the other
experts were struggling a bit as well! In both cases the past presence of
trees was the only rational cause of influence.
The notion that staged removal of a tree might alleviate damage is
interesting. In theory it shouldn't work because if soil is going to reach
an end volume, the magnitude of movement would be the same however long it
took - wouldn't it? Hmmm
The thing is, as Jon says, no-one really knows with any clinical certainty.
Enough already, supper awaits!
Jim
-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info
[mailto:uktc-request@xxxxxx.tree-care.info] On Behalf Of Jon Heuch
Sent: 20 January 2021 17:55
To: UK Tree Care
Subject: Re: Heave Risk Assessment
Bill
It's an interesting question. Similarly, one engineer who I have worked with
for some years, asks the question why didn't they have lots of heave claims
after the 1987 storm? (they didn't)
Heave is a comparative rarity; there is very little data on it. A few NHBC
claims for new houses. And of course once a tree has been removed there is
no need to involve an arborist so routinely a claim for heave does not
require an arb to do anything with trees. We may not hear about such claims.
It's the rarity that causes the mystery. A few famous documented cases. Next
time you go to Windsor Great Park you need to pick up the case documenting
movement in one of the buildings there.
Cutting a tree down in stages means that no-one has any idea of the history
as the whole process lasts years rather than months, making life even more
complex. It sounds good but we have no evidence it makes any difference.
Jon
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