damp patches on new plaster- pattern follows adhesive patches

[chi6se]

Hi Guys and Gals,
I've recently removed all old plaster from my living room and kitchen. The plaster was 'blown'. So plasterboards were used to cover the bare bricks using dot and dab, followed by a skim coat of plaster. Watermark started to emerge after a few months. We were advised to remove the plaster from the floorboards. We removed 10cm of the plasterboard all round the walls. The water mark progressively spread, up to 12 inches. I have removed it up to 12 inches. My question is where is the water coming from? All usual checks were done, i.e.
chimney repointed
outside wall repointed
gutters cleaned
downpipes renewed
additional airbricks inserted
doors renewed
drains checked,and cleared.
Any ideas? Should I call the experts?

 

[ree]

You are talking to experts - only we are not on site.

1. Why not post pics of these marks and stains?

2. Why was the original plaster "blown"?

3. Is there a chimney breast in the vicinity?

4. Do you have a cavity wall? Or a solid floor?

5. Do you have cavity insulation?

6. Is the house rendered?

7.Opening the bottom of the plasterboard allows air behind the p/b where it often creates condensation and mould.
D&D should never be "ventilated".
Hard plaster in contact with solid floors should be cut back 50mm.

 

[chi6se]

Hi Ree,
Thanks for the questions.
The original plaster was 'blown' due to water damage and poor ventilation. We have a wood burning stove in the middle of the living room. It is a single skin between the kitchen and the living room. The floor in the kitchen is concrete whilst the one in the living room is wooden floorboards. The house is not rendered. Our house was very unfortunate in that it was not meant for cavity wall insulation. I think the DPC was breached in kitchen; we discovered the slate DPC when we were knocking off the plaster! So, the source of water ingress is a bit of a mystery, to say the least.

 

[ree]

Why not post some pics of both rooms and the chimney breast(?) with the "wood burning stove"? And external pics of the outside walls to the kitchen and living room?

Is this a stone cottage or a brick terraced house?

If you have a slate DPC it must be an older house - are you sure that it has a cavity? How thick are the walls?

The plaster would have bridged the DPC if it covered it - can you post a pic of the lower wall in the kitchen?

 

[cAtLeYx]

Do we assume the damp patches are purely showing on the inside face of the external walls only? Having them evident on the internal (room diving walls) would be something completing different and I would suggest very unlikely..!! As previous posters above the problem that caused the plaster to blow has not been remedied but now simply been covered over.

 

[theprinceofdarkness]

No the problem is condensation, where the dab glue is on the plasterboard it is as cold as the outside wall. In other places its warmed by the room's heat. Increase the ventilation and heat in the room and they will disapear.
Frank

 

[cAtLeYx]

So to confirm, you have damp penetrating the adhesive "dabs" on internal walls (walls dividing your rooms from each other), (visible damp patched) and that you believe this to be condensation. This doesn't seem right. Condensation is warm moist air that will penetrate porous surfaces until until cooling takes place and causes it to form water droplets. Is it all over of just the lower sections of the internal walls, Did you not say the original plaster had blown.We need a few photos please.

 

[cAtLeYx]

Sorry I should of added. As the external elevation of your house will be colder than the internal, all moisture will naturally percolate to the inside - Extra heat and ventilation will only add to draw the moisture out of the building fabric, yes I agree on inspecting the surface of the walls may appear dryer.. If the cause is not rectified its like drinking a glass of water through a straw. The more you suck, the more that come out. You need to empty the glass of water..!!