Newly Half-tiled bathroom, upper plastering showing large damp areas.

[JimboMarimbo]

I was advised to have only the lower half of a completely renovated ground floor bathroom tiled, as there would be "a condensation problem when showering or bathing" if wholly tiled, floor-to-ceiling. Apparently the plastered upper area would be better at absorbing excess moisture whereas it would run - stream - off the tiling. Hmm.

I did the ceiling with 50mm Celotex and then had the whole empty room re-plastered, prior to installation of the bathroom fittings.

I should say that the bathroom is a ground floor extension with roof, left and right sides open the elements - just one wall and door through to the rest of the house.

First sign of cold weather and large damp patches, mirroring the breezeblock/mortar layout have appeared. The tiling shows no signs of unusual dampness. This seems the opposite of what I was told - i.e. that the plaster areas would absorb any moisture.

I would ask this forum for advice. My thoughts being to either tile the upper area to match, or 10mm plasterboard and finish with wallpaper.

Obviously the plasterboard option will be cheaper and easier, but how to stop the ingress of cold in its tracks. Spot and dab adhesive will leave space behind the plasterboard - potentially providing an area of motionless air - a good insulator, if sealed around the edges. Tiling would be a permanent fix - but would it be as effective as a block to the cold/warm interface that threatens to wreck my new facility?

 

[stevethespreader]

on having this advice did they advise you to have an air brick or extractor fan? thats a bad case of condensation are the walls solid ? what backing plaster was used?

 

[JimboMarimbo]

Thanks Steve, the original 1970s wall covering was 10mm concrete over breezeblock with a plaster finish. The renovation plasterer skimmed another smooth layer of plaster over the existing after making good, giving three layers in all.
The extractor fan was not installed owing to the bathroom installer 'not doing electrics' so the existing rectangular 'hole in the wall' is just loosely filled with draughtproofing felt - which could easily be removed.
D'you think that an extractor fan would be the way forward?
Couldn't hurt, I'm thinking.
Idea was to keep the cold out, hence stuffing the hole with felt - reckon I've caused this problem myself. Duh.

 

[stevethespreader]

you need something to deal with the condensation i just have an air vent that i opened up not sure that would be enough in your case are the walls solid or cavity? are you using a good bathroom paint ?

 

[JimboMarimbo]

Steve,
I have emptied the vent hole to reveal an 8” deep wall to exit tile, knocked through what looks like solid breezeblock leaving an 8” x 5” hole in the wall. I had hoped it might be cavity breezeblock, but no such luck. I will have an extractor fan wired in to this position.

As for paint: for the upper portion of the walls and ceiling, I just used what was left over from internal decorating ‘Leyland Trade Contract’ brilliant white, coloured with Dulux bathroom – a taster pot of grey. So basically emulsion.

Do you think the combination of an extractor fan plus over painting with genuine Dulux Bathroom would solve, or at least greatly improve, the situation?

BTW thanks for your time.

 

[Mr Chibs]

I was advised by BCO to use heavyweight polythene sheeting before plasterboarding when doing my new kitchen roof, water vapour was the reason.
The polythene would stop water being absorbed, so would also block it coming through.

Perhaps if you want a 'quick' method, you could do this, then overboard with plasterboard, (not sure on fixing) downside, also, it will sit proud-er than your tiles.

As others have said, deal with the ventilation, air the room after use.

 

[JimboMarimbo]

That's interesting, Mr Chibs.
I can see how polythene sheeting twixt wall and plasterboard would block water coming through (from outside), not sure if it would have any effect on internally generated water i.e. condensation 'being absorbed'.
However, I'm coming 'round to the idea of this over plasterboarding treatment myself, as my tiles are large format and 10mm thick, same as my plasterboard, so would be barely noticable when painted - with Dulux Bathroom+ of course
How to fix this 'sandwich' to the wall? Clearly any form of adhesive will not work on polythene sheet, but carefully drilled and bugle-screwed should hold firm.
A pity that there is not a form of thin plasterboard with a foil backing (like Celotex), or if there is I've not found one!
Better get Googling...

 

[stevethespreader]

downstairs bathrooms situated at the back are cold at the best of times and this situation is far from ideal what have you got on the outside walls render? would you think about external insulation? as for the inside i would add an air extractor and i would tile up to the ceiling or maybe gut the bathroom and add insulated boarding

 

[JimboMarimbo]

Thanks to you all for walking me through this: the far-from-ideal situation of the bathroom sticking out into the elements on 3 sides plus roof I'm stuck with.
The outside walls are rendered and sound, the roof Celotex on inside and new rubber skin with cavity filled with insulation outside.
With focus on the inside, I find that there is an answer - with a bit of googling the exact same item I need pops up*. Foil on plasterboard. At 12.5mm it will be proud of the tiling by a bit, but give a major insulating layer impervious to moisture and much cold. I'll be buying this and to heck with the expense!
* http://www.insulationshop.co/12.5mm_knauf_vapour_panel_foil_backed_plasterboard.html

 

[stevethespreader]

I'll be buying this and to heck with the expense!
* http://www.insulationshop.co/12.5mm_knauf_vapour_panel_foil_backed_plasterboard.html

in that case knock the tiles off and insulate the whole wall "edit" how are you planning on putting the board up?

 

[JimboMarimbo]

Shan't be taking 'start from scratch' route, as the room is now in daily use. The tiles stay put!
I intend to fix the foil-backed-plasterboard by screwing the sheets to the sound plaster, sealing the edges and joints.

 

[Lower]

Bathroom paint will stop the condensation being absorbed by the plasterboard and changing its colour, but you may get condensation running down the walls. Are you getting condensation on your tiles?

An extractor can only help by removing some of the water vapour that is condensing on your walls. Both paint and extraction will help with the mould problem you have round the window.

 

[JimboMarimbo]

Agreed - there's a double trouble - fix-one-thing, and end up with another.
The tiles at present are not streaming with wet, that's all on the plaster, but, undoubtably once the foil/plasterboard interface plus bathroom paint is installed, there will be a new problem, only to be solved - contained - by ventilation and fan extraction.
But, at least, and crucially given the building's weather exposure, there will be no moisture coming in from outside triggered by the temperature differential.