Advice on how to treat damp in wall

16 Aug 2016
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United Kingdom
I think this wall may have rising damp (see pics). Internal floor is wood, walls are brick, internal original plaster that's been skimmed at some point; external walls are rendered/pebble-dashed.

The plaster had blown in some spots. Hacking off showed plaster base coat was darker in places, maybe damp up to about 2 foot. Top coat didn't take much persuading to come away. The skirting board seemed fine, no sign of damp. Some white powdery stuff on bricks.

Can anybody advise on best way forward. Should I tank then replanted this wall or could this be more serious?



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Trist, good evening.

Generally how long has the plaster defect been visible?

If it were long standing / severe rising damp then rear face of the skirting would have been rotten.

It is possible that your plaster problem is "relatively - new??"

Has the external ground been moved, possibly above the DPM?

What condition is the pointing around the window? and is there any damage to the external sill of the window? __ and any cracks in the external roughcast?

Does the wall have retro-filled cavity insulation installed?

why not hack off all plaster to window board height and to right and left along the wall - carefully remove the skirting.
pull nails through the skirting, and remove wood skirting fixing plugs from the wall (they rot).
then post photos of the internal wall, and pics of the other external side of the wall.

find the DPC's in both internal and external walls.
check the edge of the wood flooring for any signs of decay.

what drew your attention to the possible damp signs in the first place?
Thanks for your replies, only just had a chance to get back to the wall.

The plaster has been affected for a few months, it had blown in a few places and white powdery stuff was visible in some areas.


I'v hacked off more plaster and pulled up the floor boards. The timber feels dry (although it looks like woodworm's had a go at some point).

IMG_6879.jpeg IMG_6878.jpeg

The bottom of the air vent is level with the ground level outside and when it rains the dust around the bottom of the vent is damp.


Does the wall have retro-filled cavity insulation installed?
No filled cavity.

check the edge of the wood flooring for any signs of decay.
Can't see rot other than what I think is woodworm

What condition is the pointing around the window?
Pebble-dashed outside, all seems ok

What's would be the best way to handle this?
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there's a good chance that the timber plate that the joist tails are sitting on is rotten - rotting away out of sight underneath the plate & at the back. there's no DPC wrapping under and behind the plate.
probe deep into the plate and the joist tails with a small screwdriver.

the external ground level has been raised too high, and any DPC has been bridged by the smooth render.
at least cut the render back about 50mm from the ground. look at the greenish bridging damp signs.
best practice would be to lower the ground level one course below the air brick.
clean out all sludge from the air brick openings.
how many air bricks are present on that elevation?

your "blown plaster" photo shows what looks like rising damp signs. any sign of a DPC on the internal skin?
you could always rermove a few bricks and check for cavity bridging - cavities sometimes fill a bit with bricklayers snots.
a clear cavity could be saving your joist tails & flooring.
fwiw: read some of my earlier posts on dealing with rising damp - or use the search button.

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