On 9 Mar, 20:57, John Rumm wrote:
wrote:
Strands are for the purpose of conduction of nutrients from the hyphal
front not water to it. The strands are thought to have evolved to
reduce water loss in this process. Water at the hyphal front is
abstracted from the atmosphere not along strands
This was published in 1981 *by DH Jennings at the University of
Liverpool using C 14 glucose to follow the nutrients - mostly in
trehalose. The conclusion was that one needed 95% RH for DR to
flourish.

Ah, not heard that before... I appreciated that they strands were taking
nutrients back, but had also read (presumably incorrectly) that they
also carried water to the front (which I presume is also needed for the
digestion of the timber's cellulose by the fungus).

Dry rot can only continue to "eat your house" (after the water source
has been fixed) if the interstices are at an RH of greater than 95%
and that only happens when the masonry is very wet and acts as a
reservoir. it also has to be alkaline as cement mortar does not suppor
the dry rot. This is not common so most dry rot dies when the water
source is fixed. That is most *- not all!!!

What would you say to the oft repeated advice that plaster should be
replaced with cement based render? Quite often you see this done on
solid walls with lime mortar. It would seem that this will make the
process of the wall drying even slower?

If, however, you have active dehumidifiction you will cure it and
after a year at *normal ~RT it will die

What is the best way to apply the dehumidification - i.e. just running
an ordinary room dehumidifier in the vicinity while keeping the side
exposed, or are there other ways?

--
Cheers,

John.

/================================================== ===============\
| * * * * *Internode Ltd - *http://www.internode.co.uk* * * * * *|
|-----------------------------------------------------------------|
| * * * *John Rumm - john(at)internode(dot)co(dot)uk * * * * * * *|
\================================================= ================/

Dear John

Answers to your two questions
What is the best way to apply the dehumidification - i.e. just running
an ordinary room dehumidifier in the vicinity while keeping the side
exposed, or are there other ways?

Isolate the rooms or areas from any other water sources by shutting
doors and windows and sealing any porous walls such as internal stud
walls by lining with polythene or the like and draught stripping
provide dry heat
install dehumidifer

It is often practical in buildings in the summer simply to open all
the windows in the day and get solar gain and dehumify at night
In the winter just do it all the time!

What would you say to the oft repeated advice that plaster should be
replaced with cement based render? Quite often you see this done on
solid walls with lime mortar. It would seem that this will make the
process of the wall drying even slower?


We never recommend removal of plaster unless it is covering up timbers
that are damp or at risk
Plaster removal is often overdone particularly in listed buildings
where I go to great lenghts not to take it off if possible

If lime plaster is removed there is a cogent argument to put back
lime
I only use cement within 1 m of the ground when there is a history of
hygroscopic salts contaminating due to years of rising damp or when
the building is so modern that it matters not if you use cement

Cement will slow down the drying of the walls but equally it will
provide an instant dry surface for putting on joinery timbers at risk
such a skirtings or architraves and the water in the brick cannot
therefore go out internally but has to externally
even if it stays there it matters not as the plaster acts as a dpm

Chris