Mike wrote:
Hi
Long story but i'll try to not to go on for ever!. We had a 'pro' in
who injected DPC and re - plastered bottom metre or so of our ground
floor to solve rising damp. 6 months on we still have some damp and
have now given up on trying to get hold of the guy that did the work.
This is our first house and we simply cannot afford to pay anyone else
so need a DIY fix.
To be fair the job is not an entire disaster as it has worked in areas
where cement / sand undercoat was used. We opened up a chimney breast
before dampwork was done (to about 6 feet for a cooker) and for some
reason the guy has used plasterboard in this area plus in one other
small area of wall. We now appear to have penetrating damp in these
plasterboarded areas. you can clearly see damp circles where the dabs
are holding the plasterboard to the wall which get noticably worse on
wet days and salt crystals have formed on the surface of these
patches.
My guess is that the DPC is fine and the plasterboard is 100% the
problem (i know chimney breasts are problem areas but the other area
of plasterborded normal wall has the same problem and either side of
it is fine)

My guess is yo are wroing, and the chimney isn't properly proofed, and
never could be,which is why he used plasterboard, knowing it would last
long ENOUGH before you noticed and stopped the cheque.

I'm guessing i need to rip out the plasterboard and re plaster as per
the rest of the house. Looking for a blow by blow run down of how to
do this, in particular how to treat / prime the brickwork, ratio of
mix for the undercoat and which damp proofing additives to use in the
mix (also not sure if i need to use additives in the skim coat?
Thanks to anyone who got through that lot and any advice will be much
appreciated.


If this is an *outside* single brick wall, then this may work..rising or
penetrating damp can escape outwards and as long as you waterproof
rendering goes up high enough, it will have gone before it gets inside.

What worries me is the word 'chimney' - is it capped/vented? It may be
rain coming *down* the chimney, in which case you may bed up sealing it
in...
Another solution for outside walls is to stick up a vapour barrier (poly
sheet) and studwork with insulation and dry line with foil backed board.
As long as the timber is away from the wet walls, it won't rot, as long
as the walls are not waterproofed OUTSIDE to prevent them breathing.
Actually it will still work then,. but rising damp plus frost may make a
nonsense of the bricks..