On 31 Oct, 10:57, wrote:
wrote:
On 29 Oct, 12:14, "Chris Styles" wrote:
Hi,

A friend is looking to buy a Victorian Terraced house, and it doesn't have a
damp course.

After spinning her an elaborate story about having the entire house sliced
out of the terrace and lifted up on blocks while a damp course is fitted, I
promised to ask around to find out how much she should expect to pay to have
a chemical DPC done.

I seem to recall someone else having the chemical DPC, and it requiring a
certain amount of replastering to be done after, because the plaster had to
be stripped back at the bottom of the wall. Is this normal (or even anything
to do with the DPC?)

Any hints, tips gratefully received.

Chris

Dear Chris
An awful lot of unscientific, unsubtantiated assertions are made about
rising damp. You do not have to look further than the opinions
expressed above to get a feel of it.
As best I can I will give you a resume of what happens.
Rising damp is caused by the migration of a solution of inorganic
salts from the ground into the plaster and bricks of a wall over a
long period of time - decades. It is NOT water per se that is the
problem but the water that is abstracted from the atmosphere at times
of high RH.
The reason the BRE experiment did not work is probably because the
chaps doing it could not reproduce the conditions in a building over a
period of say 50 years. I happen to know most of them and they are not
the only ones to have tried the idea of putting brick columns in ponds
of water and testing dpcs this way. ~The University of the South Bank
did a similar experiment with similar lack of sucess and drew a
disimilar conclusion.
Rising damp does exist. It is not particularly rare. The problem is
the specialists do egg it a lot and class bridged dpcs and latereral
penetration as rising damp. That may account for more than 50% of the
houses treated - unnecessarily! Plastering is NOT always needed and
not necessarily for 1 m - the standard distance. That is normally to
protect the interests of the company rather than the client. When my
firm was contracting in this field (1979) we did it for 1 year and
decided that it was simply not worth doing because the profit margin
was too low and most of the houses we visited did not have true rising
damp needing treatment. We got calls out for condensation - pipe leaks
- bridge dpcs - you name it!
your friend needs to do several things
1) establish that there really is no dpc - they have been mandatory
since 1886 and could have been bridged by soil and concrete paths
2) IF NO dpc - then borrow or buy a damp meter and plot readings in
all walls on an isometric sketch of the affected areas over a period
of several months at times of high and low RH. Any variation in the
tide mark indicates RD. There should be a pattern of readings
starting from the top of no damp at say 1 m down to very damp at say
800 mm then slightly damp below that at the top of the skirting.
check the skirtings - are they wet (greater than say 14 w/w ) if so
you may have some form of dampness
3) get at least three free surveys - select using the following
criteria a) full members of the PCA (ex BWPDA) b) offering GPT back up
guarantee c) most importantly insist the surveyor has the CSRT
qualifiation
these three will not ensure you get a good survey but will cut out
an awful lot of crap
4) USE YOUR COMMONSENSE in intermpreting the results and dont take
them as Gospel - most firms have their intersts at heart
5) If there is dampness but the plaster is not visually damaged - take
a risk - put in the dpc but delay the replastering for a year and see
if it dries out - that saves a lot of money
6) understand that the rising damp does not occur in the bricks so
drilling the bricks is a waste of time- It occurs in the mortar. Ask
the firm if they drill the bricks (trick question) If they say "Yes"
show them the door and explain that you wanted someone who understood
they needed to drill the mortar not the brick to put the hydrophobic
layer in the mortar
7) the best dpc (in my opinion) is one using a silane based compound -
trade name "Dryzone" from Safeguard Chemicals - you can buy it and diy
See the website
Costs - these vary from firm to firm but a good diy can negotiate
reductions by taking off skirtings where needed for them and doing the
hacking off themselves

8) read up on the BWPDA (now PCA) code of practice for DPC s which is
similar to that of the BS which is also worth reading
Both are a bit out of date but show the principles.

Come back to me if you need further help
Chris

fair bit of misinformationn here too

NT- Hide quoted text -

- Show quoted text -

Dear meow2,
Particulars (of misinformation) please?
Chris G