UKTC Archive

Re: Dampness caused by trees

Subject: Re: Dampness caused by trees
From: Scott Cullen
Date: Jan 02 2007 13:14:10
I have not seen any research about trees causing interior dampness.  I know 
through experience that trees either close to a building (as in the wind 
screen evergreens) or over a building even quite far above can limit the 
dryig of exterior surfaces.  I'm not at all sure trees CAUSE dampness.  There 
either is rain or atmospheric humidity or their isn't.  But they do limit 
drying.  It is very common to see mold, mildew and green moss discoloring 
buidling surfaces under or behind trees.  Painters and roofers love to point 
this out and would prefer to have all trees out of their way.

I suppose in there is dampness (humidity) inside a building, and the sun is 
allowed to warm an outside wall radiently, the inside walls may warm by 
conduction (the inverse of preventing heat loss to winter winds).  And if the 
inside wall is warmer there is less condensation likely on those surfaces.  
Of course the level of insulation is a factor.  

And as Adam has discussed, one explanation for fewer tall shade trees in UK 
is that the shade isn't needed.  So is there enough sun to warm by conduction 
anyway?  Dunno.  

I also recall living in Dublin in the '60s when nobody had central heat.  
Through much of the year the interior of the house would stay cooler than 
outside air until mid-day.  With no trees.  

I would think an easy empirical test  would be to look for variations in 
dampness in interior walls in similarly constructed and located structure 
with and without trees.

  ----- Original Message ----- 
  To: UK Tree Care 
  Sent: Tuesday, January 02, 2007 6:54 AM
  Subject: Re: Dampness caused by trees

  It's got to be more than just wind-shelter and light shading hasn't it as
  otherwise all modern detached houses (built 0.5m apart) and properties with
  a wall or fence, shed or building close by would suffer similarly too-
  unless these are all old properties with porous bricks and solid walls.
  Clearly it's not a problem in all (most) cases.
  Do our N.American cousins suffer this who love to plant big evergreens on
  the wintery side of the house? Many people also grow climbers all over
  their houses which is a much closer association.
  I'm not sure how big a factor the trees are as against an unfortunate
  combination of other factors (soundness of guttering is a first check).
  There are also good silicone water repellents available now to treat porous
  Perhaps though the barrier effect of leaves or stomata have some effect,
  some kind of exudate or simply an exchange of biodiversity between tree and
  wall? If the accused was anything but a tree would the first suggestion be
  to pull it down as a first course of action? Perhaps an exploratory prune
  to see if this has any impact is a sensible first course of action instead.
  Happy New Year to all.

  <<How do others respond to the complaint that 'this tree is making the
  wall of my house damp?'
  How much effect does wind-sheltering and light-shading (let's say by a
  biggish evergreen) really have on a building?
  Does it actually result in penetrating damp?
  How can it be demonstrated that a tree does or does not cause dampness
  without the practical (but rather final) experiment of felling it?
  Has anyone carried out that experiment and if so, with what results?
  And, is there any literature on the subject?
  (Anyone know if the BRE book "Understanding dampness" would justify its
  £42.50 cover price, or is it all about bridged cavities and blocked
  Jerry R>>


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