UKTC Archive

Re: Subsidence

Subject: Re: Subsidence
From: Wayne Tyson
Date: Dec 07 2018 06:01:07
Thanks, Will. However, since I do not wish to be data-mined, I have
declined the download.

Wayne

On Thu, Dec 6, 2018 at 12:32 PM "willross583@xxxxxxxxxxx.com" <
uktc@xxxxxx.tree-care.info> wrote:

[Text converted from HTML]
Wayne,
Search nhbc 4.2 which is the chapter building near trees

Will

Sent from my Huawei Mobile

-------- Original Message --------
Subject: Re: Subsidence
From: Wayne Tyson
To: UK Tree Care
CC:

    Jerry and Group:

    I'm still struggling with understanding just how trees cause
    subsidence. Am
    I to understand that the extraction of water from clay soils is
    the primary
    issue?

    Wayne

    On Thu, Dec 6, 2018 at 4:25 AM Jerry Ross wrote:

    > Writing as someone who lives and works in an area without heavy
    clays,
    > I'venonetheless been asked to look at numerous tree-related
    subsidence
    > claims. They are usually for trivial and certainly for
    non-structural
    > damage and not uncommonly the evidence presented is, to say the
    least,
    > dubious.
    > But there's always a claims management company going after the
    tree (or
    > the tree owner) like a dog after a bone...
    > Poor building practice certainly doesn't help, but I'd suggest
    that a
    > lot of our subsidence 'problems' have been created by the
    industry
    > that's grown up to make money out of them.
    >
    >
    >
    > On 06/12/2018 12:05, Bill Anderson wrote:
    > > NHBC are the national house building council Wayne. A sort of
    insurance
    > > company for the development industry. They publish Building
    Standards,
    > > which their clients are supposed to follow.
    > > Debatably, our subsidence problems follow from poor building
    practices in
    > > the recent past more than anything else..
    > >
    > > Bill.
    > >
    > > On Wed, 5 Dec 2018 at 22:33, David Lloyd-Jones <
    > dlj@xxxxxxxxxxxxxxxxxx.com>
    > > wrote:
    > >
    > >> Hi Wayne
    > >>
    > >> My replies are in context...
    > >>
    > >> -----Original Message-----
    > >> From: Wayne Tyson
    > >> Sent: Wednesday, December 5, 2018 8:22 PM
    > >> To: UK Tree Care
    > >> Subject: Re: Subsidence
    > >>
    > >> I am interested in this subject, but know nothing of the
    issue in
    > Brittan.
    > >> Would anyone be interested in explaining the phenomenon in
    simple terms?
    > >> The following questions probably reflect the depth of my
    ignorance,
    > being
    > >> mere guesses. Am I to understand that this issue is common
    in Britain?
    > >>
    > >> 1. Are foundations built upon materials (e.g. clay) subject
    to excessive
    > >> expansion and contraction?
    > >>
    > >> Yes. Clays vary in volume when moisture is abstracted and if
    a tree
    > >> exacerbates the relative degree of dessication close to it,
    differential
    > >> shrinkage occurs and subsidence can result.
    > >>
    > >> 2. Are growing tree roots demonstrated to, or suspected of,
    causing
    > damage
    > >> to foundations?
    > >>
    > >> It's trees abstraction of moisture that is the problem,
    another variable
    > >> is
    > >> the relative depth of foundations, variations in the depths
    of
    > foundations
    > >> and yet another set of variables the tree's rooting
    strategy, age and
    > >> relative vitality.
    > >>
    > >> 3. Are dead tree roots demonstrated to, or suspected of,
    causing damage
    > to
    > >> foundations by leaving voids which result in subsidence?
    > >>
    > >> Only in terms of their ability to transfer wind loadings if
    they are
    > >> close.
    > >> In practice, unlikely
    > >>
    > >> 4. Are there any laws requiring that foundations be built
    upon firm
    > strata?
    > >>
    > >> No, but there are NHBC Guidelines that an engineer can use
    to calculate
    > >> the
    > >> relative depth to which foundations should extend so that
    they are
    > founded
    > >> in what is likely to be moisture stable clays
    > >>
    > >> 5. Are there regulations requiring specially-designed
    foundations for
    > >> construction on "soft" materials? If so, what are they?
    > >>
    > >> See last answer.
    > >>
    > >> 6. What am I missing?
    > >>
    > >> Historical variability of building design. I recently
    surveyed a damaged
    > >> building whose foundations extended just 37CM under ground
    on a clay
    > with
    > >> a
    > >> highly shrinkable modified Plasticity Index. That building
    and trees
    > aint
    > >> friends!
    > >>
    > >> Hope this helps
    > >>
    > >> David
    > >>
    > >>
    > >> On Wed, Dec 5, 2018 at 7:41 AM David Lloyd-Jones <
    > >> dlj@xxxxxxxxxxxxxxxxxx.com>
    > >> wrote:
    > >>
    > >>> Hi Jon
    > >>>
    > >>> All valid points that I take on board.
    > >>>
    > >>> The homeowner and neighbour both would like to keep the
    tree so I am
    > >>> merely
    > >>> trying to enable that to be the outcome along with some
    checks and
    > >>> contingency plans so that until it happens again (if it
    ever does) they
    > >>> can
    > >>> keep and enjoy the tree.
    > >>>
    > >>> Thanks
    > >>>
    > >>> -----Original Message-----
    > >>> From: Jon Heuch
    > >>> Sent: Wednesday, December 5, 2018 12:05 PM
    > >>> To: UK Tree Care
    > >>> Subject: Re: Subsidence
    > >>>
    > >>> "I am just about to specify an automated watering system as
    an
    > >> alternative
    > >>> to tree removal where just one small brick built porch is
    slightly
    > >>> affected.
    > >>> It will be the
    > >>>
    > >>> first such system that I have designed so this one might be
    > interesting."
    > >>>
    > >>>
    > >>>
    > >>>
    > >>>
    > >>> Sounds like you are trying to re-invent the wheel...this is
    an approach
    > >>> that
    > >>> has been tried on several occasions by building
    professionals..watering
    > >>> the
    > >>> foundations.
    > >>>
    > >>>
    > >>>
    > >>> It's not really a solution in any general sense:
    > >>>
    > >>>
    > >>>
    > >>> i) What's caused the dryness in the first place? A
    > >>> tree?
    > >>> If you leave it there the water you put on will disappear
    next summer.
    > >>>
    > >>> ii) How much water do you put on? Too much and you
    > will
    > >>> make matters a lot worse. Remember wet clay has no bearing
    capacity.
    > >>>
    > >>> iii) Where do you put the water? Precisely. Do you just
    > >>> leave a hose running? A damaged porch with no other damage
    may be
    > simple
    > >>> in
    > >>> this respect...but:
    > >>>
    > >>> iv) Once the top layer of the soil is wet, it will
    > swell
    > >>> and
    > >>> not let the water go any deeper. If the roots causing the
    problem are
    > >>> 1.5-2
    > >>> metres down all you will get is run-off getting nowhere
    near the dry
    > >> soil.
    > >>> v) If you have mechanisms for getting the water
    > deeper
    > >>> in
    > >>> the soil profile you still have to work out what depth and
    the volumes
    > >>> required..how do you do that?
    > >>>
    > >>>
    > >>>
    > >>> And if you want to talk to someone who has tried it contact
    Chris
    > Kawecki
    > >>> http://www.subsidencemanagementuk.co.uk/ but please don't
    use this as
    > >> my
    > >>> endorsement of the method. I don't know anyone of any
    organisation
    > >>> attempting this routinely.
    > >>>
    > >>>
    http://www.subsidencemanagementuk.co.uk/company-information/reversal/
    > >>>
    > >>>
    > >>>
    > >>> Jon
    > >>>
    > >>>
    > >>>
    > >>>
    > >>>
    > >>>
    > >>> --
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    > >>> http://www.boskytrees.co.uk/
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    > >>>
    > >>>
    > >>>
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    > >>
    > >>
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