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The Natural Philosopher

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.

Er no. In my case it appeared directly the day after heavy rain, and was
due to RAPID - hours only - build up of a lake beneath the floor, that
was sucked up by the chimney brickwork, and by another transverse wall
that had NOT been injected.

The OUTSIDE WALLS THAT HAD BEEN INJECTED, WERE FREE FROM IT.

In this matter I can totally agree with ne point

"An awful lot of unscientific, unsubtantiated assertions are made about
rising damp."

And you are the guilty party.

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.

A lot depends on the brick and the mortar, Old soft brick and lime
mortar sucks like a whore.

Put in modern cement and the mortar courses themselves act as a
primitive DPC.

Everyone KNOWS how much bricks will suck water out of mortar. The
question is what is the set mortar like? Lime mortar is soft and porous,
and no barrier to the passage of water. This may, or may not be, the
property you like about it.