Penetrating damp - sealant advice needed.


Postby LF » Tue Mar 11, 2008 1:06 pm

We moved into a Victorian terraced house a few weeks ago, which was renovated by the previous owners. Since moving in (was not present on several viewings of house) damp patches have started to appear on the rear wall.

The wall has been newly plasterboarded and painted. There is a long damp patch (4 feet) where the ceiling meets the wall, that runs about 2 inches down the wall, as if the water is slowly moving downwards, as well as several lighter damp patches at various places in the wall - a couple round the skirting board (which we've removed and cleared debris that was breaching the damp proof course but patches remain), patches around the back door recess and some mid-way up the wall.

The patches appear to get worse after periods of heavy rain and I think are cause by rain water penetration. We have what appears to be a square lead box gutter that runs to a downpipe at the side of the house. The wall is south-westerly facing and we are on a hill and it seems to get the prevailing weather (rain sounds much worse than at the front of the house). During heavy rain, dripping can be heard with water dripping from the ground, first and second floor window sills. Visually all the mortar/pointing and windown seals look fine.

I want to get a roofer (is that best person?) to check gutter for leaks/blockages and then we planned to leave the wall until the summer and seal the exterior with a waterproofing sealant. Is this the right thing to do? I've heard it can stop the house 'breathing' and make things worse?

Any other suggestions?

Thanks
LF
Posts: 4
Joined: Tue Mar 11, 2008 12:51 pm

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Postby ALDA » Tue Mar 11, 2008 10:29 pm

LF,

Seems like the water penetration is being soaked up by battens to which the plasterboard is attatched.(doubt its dot and dab fix).

In my opinion only, the wall should have had a waterproof sheet applied to it before fitting battens and boarding.

The walls have got to be sealed in some fashion to prevent the problem with an internal wall surface fitted in this way to walls not designed for this!!!

So the question is internally or externally sealed?

It will originally have been lime plastered(which is breathable) but former owner either did not know of this or did but didn't want the hassle of, or expense involved in replacing old plaster and so opted for useless quick fix.(to get the house sold maybe?).(any form of redress hear?).

Do you keep the boarding and seal outside?
or
remove and re-lime plaster?

Are there any other rooms that are on this wall with plasterboard fitted?
Yes or no, is there any water ingress?(think plaster- think boarding)!!!

Do make doubley sure that there is no other route for water to get in and that there are no problems with gutters leaking.

Use an experienced builder(recommed by family ,friend or neighbour)to assess and advise on problem and get a quote too.

Then you can make the decision of wether to diy or gsi.

regards,

ALDA.
ALDA
Posts: 397
Joined: Mon Feb 04, 2008 8:15 pm


Postby LF » Wed Mar 12, 2008 1:12 pm

I think the plasterboard is 'dot-and-dab' - Don't know much about it but a builder/damp proofer who came to look did mention that when they came round - said it might be condensation in voids where not enough adhesive was used during dot and dab process and that a foil-backed board may not have been used. Doesn't seem to be condensation to me though as is worse in the rain (i think) and some patches look more damp than I'd imagine condenstaion would cause.

The wall doesn't sound hollow all over when you tap it (as I assume it would if the plasterboard was supported on batons) but has some hollow sounding areas and other solid bits.

If the plasterboard was removed and re lime-plaster properly, would this stop rain water penetration from the external wall? Or would we still need some other seal? There are no obvious wet patches on the external wall (which is painted).

Thanks
LF
Posts: 4
Joined: Tue Mar 11, 2008 12:51 pm


Postby ALDA » Wed Mar 12, 2008 7:12 pm

LF,

SOUNDS LIKE A POOR DOT AND DAB JOB!!!

I DOUBT IT IS A CONDESATION PROBLEM TOO, UNLESS THERE ARE CRACKS OR HOLES IN THE NEW BOARDING TO ALLOW WARM MOIST AIR TO ENTER VOIDS AND CONDENSE OUT BETWEEN BACK OF BOARDS AND ORIGINAL COLD WALL SURFACE.(BUT WE BOTH COULD BE WRONG).

YOU SAY THE EXTERIOR WALL IS PAINTED!
WITH WHAT?
IS IT IN GOOD CONDITION OR PATCHY/BLOWN?
IS THE WALL PAINTED RENDER?

IN VICTORIAN TIMES, BECAUSE THEY HAD OPEN FIRES WITH CHIMNEYS(ie GOOD HEAT AND VENTILATION)
AND BREATHABLE PLASTER ON WALLS DAMPNESS AND CONDENSATION WEREN'T A PROBLEM.
(MOISTURE DID GET IN BUT WOULD IMMEDIATELY EVAPORATE OFF AND WOULD NEVER BE NOTICED).
THATS WHY I SAID THESE WALLS WEREN'T DESIGNED TO BE LINED IN ANY OTHER WAY THAN LIME PLASTER.(BREATHABLE)!

THIS IS WHY I ASKED IF YOU HAD ANY OTHER PLASTERED WALLS WHICH PRESENT A PROBLEM?(I DOUBT YOU DO)(ONLY BOARDED WALL PROBLEMS).

PERSONALLY, I WOULD, ENSURE THERE IS DEFINATELY NO MAJOR RAIN WATER INGRESS THROUGH POOR MORTAR POINTING/MASONARY CRACKS/RENDERING/DPC OR PROBLEMS WITH GUTTERS/DOWNPIPES/OVERFLOWS AND ONLY THEN RE-PLASTER!

WHAT EVER YOU DECIDE TO DO, THE EXISTING BOARDING HAS TO COME OFF IN ANY CASE TO FIND OUT EXACTLY WHAT THE PROBLEM IS BEHIND AND TO RECTIFY.

CHEERS,

ALDA.
ALDA
Posts: 397
Joined: Mon Feb 04, 2008 8:15 pm


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