Hello + moisture resistant board advice

Mat800

New Member
Hi All, I'm a new member looking for some advice to sort a wall in my bathroom. Does anyone have experience with the Gyproc or Knauf moisture boards? I’ve done some plastering before, but I’m a bit uncertain with this situation:

Upstairs bathroom rear extension on Victorian terrace, solid brick walls, flat roof. Ceiling had small damp patches where it meets the wall, hopefully due to condensation on cold wall and moisture from disused airbrick (I found 3 empty soaking wet Board Finish bags stuffed in there). Flat roof is in good condition, no evidence of moisture in roof cavity. I've hacked off loose plaster, so after sorting the airbrick and drying the wall out, do I:
  1. Fix mesh over timber beam, use Sand/Lime/Cement scratch+float, then skim OR
  2. Square up and dot/dab a piece of moisture board in (I can tuck it up behind the ceiling), skim.
Or something else? Thank you in advance. Mat
 

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Hi All, I'm a new member looking for some advice to sort a wall in my bathroom. Does anyone have experience with the Gyproc or Knauf moisture boards? I’ve done some plastering before, but I’m a bit uncertain with this situation:

Upstairs bathroom rear extension on Victorian terrace, solid brick walls, flat roof. Ceiling had small damp patches where it meets the wall, hopefully due to condensation on cold wall and moisture from disused airbrick (I found 3 empty soaking wet Board Finish bags stuffed in there). Flat roof is in good condition, no evidence of moisture in roof cavity. I've hacked off loose plaster, so after sorting the airbrick and drying the wall out, do I:
  1. Fix mesh over timber beam, use Sand/Lime/Cement scratch+float, then skim OR
  2. Square up and dot/dab a piece of moisture board in (I can tuck it up behind the ceiling), skim.
Or something else? Thank you in advance. Mat
Wall looks dry I’d use hardwall as backing coat then skim it for such a small area , and put air vent back in where it’s been blocked up
 
Thanks, that would be quicker/easier. Haven't made my mind up yet over putting the vent back in, it's a choice between extra ventilation (already a fan on the opp. wall) and not making the wall surface any colder than necessary.
 
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