Damp and Plastering Options

[mika_98]

Hello all, Desperately in need of some advice please (would also put my mind at ease too).

Currently in the process of re-plastering my front room and after removing all of the old plaster, unfortunately we have found a few areas of damp. One is on the chimney face (which we may remove) and we’ve found the cause of that being a slight leak in the chimney pot/cap. Another is to the left of the chimney, heading towards the front of the house. This rises up to about 30-40cm and covers a width of about 2-3ft. Its exactly where a bookcase had been pushed right up against the wall, it had been sat there for about 10 years! So I’m wondering if this damp area is due to the wall not being able to breathe effectively. All other walls seem to be fine, apart from the two small areas where patches of moisture are visible on the brick and in the mortar, rising to about 15cm max (skirting height), about a foot or so wide.

I’m waiting for a visit from a builder on identifying the cause some of the damp areas. But in the meantime, I would be very grateful to receive some advice on the finishing process for the walls please. Waiting for the moisture to dry out will take a LONG time so my initial thoughts are:

1) Stud/Batten walls > Board > Skim. But I'm unsure on which type of board to use. Do I go for a vapour/foil backed board or moisture resistant (green) board? This also brings the issue of applying insulation in the gaps between board and brick. Does the insulation material have to be applied from top to bottom? And can I just use any type of board/insulation roll or should I avoid certain types due to the moisture problems?

As for the battens, I'm thinking treated timber or roofing battens. I was advised to apply foil tape on the face of the battens which meet the plasterboard, especially up to a metre from the floor up. Is that really required? :S 

2) Insulated plasterboard applied with adhesive. My only worry here is moisture coming through the dabs of adhesive leading to patches of damp on the plaster. I heard elsewhere that condensation could collect on plaster where dabs have been applied. Not entirely sure if this is true though?

I guess it’d help if I add some detail about the property :) It’s a terraced house, not exactly sure on the age but I’ve been advised it may have been built 1920 onwards. Solid red brick walls with no cavity. I look forward to any advice. Many thanks :D

[sammy.se]

Hi,
Quick answer: You should plaster in Lime, if you want the wall to breathe.

Long answer: you've identified the cause of the chimney breast damp, it seems.

Regarding the corner damp, can you please check and let us know:

What is on the other side of damp walls i.e. each of the walls which make the corner?

Where are the other two patches of damp? Are they on walls which are external (meaning the other side is outdoors?)

Is this ground floor?

Do you have any pipes running under the floor boards on the room, of so, from where to where?

[sammy.se]

Can you draw a diagram of the layout, showing the damp areas and position of pipes, air vents and gutters/drains please

Also, is the floor wooden?

Thanks