Fibre Cement Board Bathroom Ceiling Skim

Members online

l.j.nash

New Member
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.
 

ChrispyUK

Well-Known Member
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.

just use Pb and skim it or clad it with plastic, as mentioned, you’re well over thinking this. I fit loads of bathrooms so you can trust me :coffe:
 

Stevieo

Royal Spin Doctor
And viruses stats and figures and graphs pie charts racism mortgages ford transit van finance,accounting arrears ccj's debt collecting vaccine technology nhs advocate ball bag stretching and spreading probably missed a few off there
That's @Casper you're thinking of.
 

ChrispyUK

Well-Known Member
You had all your jabs Wee man ?
9DAFAF7A-0E7A-4B04-B2AA-0B8939B402A0.jpeg
 

MakeItSmooth

Well-Known Member
And viruses stats and figures and graphs pie charts racism mortgages ford transit van finance,accounting arrears ccj's debt collecting vaccine technology nhs advocate ball bag stretching and spreading probably missed a few off there

I disagree with 99% of Nath's opinions, and the way he calls other people stupid, but I happen to agree with his dislike of racism.
 

Tinytom

Well-Known Member
Sounds like overkill, you can skim cement board with multi or board finish just pva or sbr 2/3 coats to kill the suction
 

l.j.nash

New Member
Thank you for all your replies.

Clearly I overthink everything (I can’t help it) but you all picked up on that

Options offered

(1) Plasterboard + skim
(2) Cement board + plaster skim
(3) Any kind of board + plastic cladding (can’t say I’m a huge fan of plastic cladding but perhaps someone can point me to something that doesn’t look rubbish)

I already have the cement board, so it looks like option 2 is the most sensible but also kind of the worst of both worlds.
 

Nath80

Well-Known Member
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.
Sweet baby jesus. You fitting a bathroom or a swimming pool?
Just get it done
 

plas1

Well-Known Member
Thank you for all your replies.

Clearly I overthink everything (I can’t help it) but you all picked up on that

Options offered

(1) Plasterboard + skim
(2) Cement board + plaster skim
(3) Any kind of board + plastic cladding (can’t say I’m a huge fan of plastic cladding but perhaps someone can point me to something that doesn’t look rubbish)

I already have the cement board, so it looks like option 2 is the most sensible but also kind of the worst of both worlds.
Depending on cost and if you wanted something nice like venetian/microcement howecer some will disagree.lol wedi board as it's light weight and away you go.Did this one recently.
Thank you for all your replies.

Clearly I overthink everything (I can’t help it) but you all picked up on that

Options offered

(1) Plasterboard + skim
(2) Cement board + plaster skim
(3) Any kind of board + plastic cladding (can’t say I’m a huge fan of plastic cladding but perhaps someone can point me to something that doesn’t look rubbish)

I already have the cement board, so it looks like option 2 is the most sensible but also kind of the worst of both worlds.

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.
Microcement or venetian works well.Depending on what you want to spend.This is slightly textured bit can be done smooth also obviously.
 

Attachments

  • PXL_20201120_171259565.jpg
    PXL_20201120_171259565.jpg
    2.7 MB · Views: 15
  • PXL_20201120_171328321.jpg
    PXL_20201120_171328321.jpg
    1.6 MB · Views: 16

Retired Spread

Well-Known Member
Thank you for all your replies.

Clearly I overthink everything (I can’t help it) but you all picked up on that

Options offered

(1) Plasterboard + skim
(2) Cement board + plaster skim
(3) Any kind of board + plastic cladding (can’t say I’m a huge fan of plastic cladding but perhaps someone can point me to something that doesn’t look rubbish)

I already have the cement board, so it looks like option 2 is the most sensible but also kind of the worst of both worlds.
you put skim on cement or MR board you're taking away the whole point of it being moisture resistant so it's a complete waste of time.
when you put board up just fill screw heads and paint on the board.
but if you insist on skimming them (cement or MR boards) they will need to be gritted first
 

Tinytom

Well-Known Member
you put skim on cement or MR board you're taking away the whole point of it being moisture resistant so it's a complete waste of time.
when you put board up just fill screw heads and paint on the board.
but if you insist on skimming them (cement or MR boards) they will need to be gritted first
Why does it need to be gritted? Grit is for low suction backgrounds to provide a mechanical key, not high suction, at least that’s my understanding of it
 

Brimstone

Well-Known Member
The Artex on my bathroom ceiling has been absolutely fine, smooth ripple finish, Dulux Diamond paint, been easy to clean and up for years, no problems.
 

l.j.nash

New Member
you put skim on cement or MR board you're taking away the whole point of it being moisture resistant so it's a complete waste of time.
when you put board up just fill screw heads and paint on the board.
but if you insist on skimming them (cement or MR boards) they will need to be gritted first
Filling screw heads and just painting the board would be nice (Hardie Backer board surfaces are very smooth) but wouldn’t joints between the boards still need mesh tape applying and filling, resulting in a raised line? I’ve seen a system called “Prima Ceiling Seamless” which cleverly provides a recessed board edge, allowing joining tape and compound to be placed into a channel and finished level with the board surface. A shame that Hardie doesn’t have that feature (but then as pointed out here multiple times, it is intended as a tile backer board).
 

Nath80

Well-Known Member
Filling screw heads and just painting the board would be nice (Hardie Backer board surfaces are very smooth) but wouldn’t joints between the boards still need mesh tape applying and filling, resulting in a raised line? I’ve seen a system called “Prima Ceiling Seamless” which cleverly provides a recessed board edge, allowing joining tape and compound to be placed into a channel and finished level with the board surface. A shame that Hardie doesn’t have that feature (but then as pointed out here multiple times, it is intended as a tile backer board).
Its a bathroom ceiling
 
Top