On 25 Aug, 18:15, Jeweller wrote:
I'm hoping there's a specialist around here who can help me
with advice about our walls.
It's an old house built of brick with no cavity. The oldest
bit (C1720) has solid walls 3 bricks deep and mostly these
are OK.
A later addition (C1840) has walls only 2 bricks deep and
it's these walls that are causing us some grief.
The outside is painted, (the bricks are too soft for
sand-blasting) and the pointing is apparently intact but I'm
happy to be advised on this.
The wet summer has brought damp patches inside these 2 brick
deep walls.
I am loathe to try and seal the walls either outside or
inside, the seal only breaks down sooner or later.
I feel sure there must be a way that the insides were
prepared/treated that could cope with damp weather
conditions when these walls were originally built.
We do keep a trickle vent open in the windows and the rooms
do get heated when we have the central heating on.
It's not a permanent affliction, there's precious little
damp in normal weather conditions.
Any more information needed?
Cheers
D
--
Jeweller
R100RT
Formerly: James Captain, A10, C15, B25, Dnepr M16 solo,
R80/7, R100RT (green!)www.davidhowardjeweller.co.uk
Dear D
There is one more possibility that has not been discussed and that is
the presence of hygroscopic salts in the internal plaster due to past
water penetration bringing them in. To test for this check on the
damp patches with a damp meter and see if they correlate not to the
rain (ie lateral penetration) but to the relative humidity which can
be high with no rain. I understand that the patches come and go with
the weather (rain) so you need to determine this.
If it is hygroscopicity your cure is to identify the locations (use a
pencil) over time - add a small margin for a factor of safety (say 150
mm but use commonsense) - and remove all such defective plaster and
repair with a similar plaster to the original. If it is lime then use
lime putty in tubs not bagged lime and mix up the mortar in a tub and
leave it for as long as you reasonably can (coars stuff) say 6 months
before using it. check for the presence of any hair acting as binder
and incorporate if you need to .
I was confused as to how thick the walls are. Three bricks deep is
massive and I would be suprised if you are getting penetration through
27" of brick. Are you sure that you do not mean 1.5 bricks (13.5")and
one brick (9") respectively? That is much more likely in the sort of
building you are describling.
When I was faced with exactly the same problem as you on soft red
rubbers which had been painted over by my previous owner so the outer
part of the brick had absorbed some of the paint and there were
pockets therein painted -I considered lots of options and tried
samples of all sorts of cleaners chemically and manually. None worked
and in the end I had no choice but to get to it with a dirty great
angle grinder with a face disc on it and took off the guard so I could
VERY carefully take off the outer 1mm or less of the brick. I was
told this would ruin the "face" of the brick and it would all degrade
in a few years. I could see no logic in this statement as the
material of the brick was not different on the face and 05 or 1.0 mm
in. After removal of the paint I hand rubbed each brick with sand
paper (orbital and hand sander) to remove disc marks and then
repointed it with tuck pointing using red brick dust as my sand for
the back of the tuck. I did the work some 25 plus years ago and it
looks as good now as it did then.
I endorse the other views on avoiding sandblasting and from my own
experience would urge you (unless you wish to risk getting extensive
dry rot in a couple of yeas) to avoid any high pressure water based
methods.
Good luck
Chris