I know this is the DIY Plastering forum, and not the cement board forum, but I’m hoping someone can offer some advice regarding cement board for a bathroom ceiling.
Some Background
I’m creating a shower room which I’ve timber framed to make square and allow for interior insulation. I’ve also build a false ceiling timber frame to allow for a flat ceiling and to hide a steel beam. I’m going to be lining the walls with 12mm Hardie Backer (fibre cement board) and had been planning to also use this to line the ceiling but I’ve become stuck trying to find a good option for rendering.
My Thinking
It seems that moisture resistant plasterboard is commonly used for bathroom ceilings but to me a cement board would seem to be a better long term choice (if only I can find a suitable way to render) but seemingly no one else does this? The shower room ceiling is very low and has a bathroom directly above. If there is going to be a water leak in the future, a bathroom seems the most likely place. With a cement board ceiling, it could be completely soaked and remain structurally sound and once dry could be repainted if necessary. The ceiling is also likely to experience a lot of condensation from the shower below (even with an extractor fan).
The Plan
The original plan was to fix cement board to the ceiling frame, tape the joints and then skim with some form of cement based render. The render would then be painted to provide the final finish. I’ve considered making my own mix of Portland cement, plastering sand and using SBR as both a primer (SBR+cement slurry) and additive to the mix (SBR is really wonderful stuff!). Then I found a cement based product from Ardex (A 125) which sounded ideal, “Fine Coat Smoothing & Finishing Render for Walls and Ceilings”, but after talking with the manufacturers technical support (and being initially advised this application was fine) I was told that it wouldn’t be suitable as it was not flexible and would crack across the joints in the board.
Advice?
I really would like to continue with the option of using cement board, rather than plaster, so is anyone able to offer any advice? Am I missing something that explains why this approach doesn’t seem to be used or supported? Thank you in advance.
Some Background
I’m creating a shower room which I’ve timber framed to make square and allow for interior insulation. I’ve also build a false ceiling timber frame to allow for a flat ceiling and to hide a steel beam. I’m going to be lining the walls with 12mm Hardie Backer (fibre cement board) and had been planning to also use this to line the ceiling but I’ve become stuck trying to find a good option for rendering.
My Thinking
It seems that moisture resistant plasterboard is commonly used for bathroom ceilings but to me a cement board would seem to be a better long term choice (if only I can find a suitable way to render) but seemingly no one else does this? The shower room ceiling is very low and has a bathroom directly above. If there is going to be a water leak in the future, a bathroom seems the most likely place. With a cement board ceiling, it could be completely soaked and remain structurally sound and once dry could be repainted if necessary. The ceiling is also likely to experience a lot of condensation from the shower below (even with an extractor fan).
The Plan
The original plan was to fix cement board to the ceiling frame, tape the joints and then skim with some form of cement based render. The render would then be painted to provide the final finish. I’ve considered making my own mix of Portland cement, plastering sand and using SBR as both a primer (SBR+cement slurry) and additive to the mix (SBR is really wonderful stuff!). Then I found a cement based product from Ardex (A 125) which sounded ideal, “Fine Coat Smoothing & Finishing Render for Walls and Ceilings”, but after talking with the manufacturers technical support (and being initially advised this application was fine) I was told that it wouldn’t be suitable as it was not flexible and would crack across the joints in the board.
Advice?
I really would like to continue with the option of using cement board, rather than plaster, so is anyone able to offer any advice? Am I missing something that explains why this approach doesn’t seem to be used or supported? Thank you in advance.
