Once and for all (hopefully!) CEMENT Boards Explained

[RichBD]

It feels like there is a constant asking about the suitability of cement board in wet areas.
"Will they be ok in my wet room?" "Should I tank them?" etc etc etc
Can I attempt to clear up the confusion - much of which comes from the manufacturers and the builder's merchants who sell the stuff?

First of all: WATERPROOF vs WATER-RESISTANT
I honestly want to bang my head against a wall when this comes up.

1) Waterproof means water cannot get past the board.
2) Water-resistant means ONLY that water will not damage the board's integrity.
BUT - water can still soak through the board to the background.

Cement / Silica board - I class as Hardibacker / AquaPanel / NoMorePly
These are NOT WATERPROOF. They are sold as suitable for showers / wet areas etc and in my opinion they should not be sold as such. They are only "suitable" in as much as they won't get damaged by water - but unfortunately in my experience they will allow water to damage everything else - your tiling, your timbers and your rooms next to and below the one they're in!

The negatives of these boards:

• Heavy
• Difficult to cut
• Slow to install
• Contain silica dust (v harmful)
• NOT WATERPROOF - require tanking to make waterproof.

(note that tanking will reduce inherent weight-bearing though)

The positives:
- very strong and can take great amounts of weight

OK - Waterproof Boards now:
I class as Schluter's Kerdi board / Wedi board / Marmox board / Delta Board - there are others claiming the same properties but I can't vouch for them.
These boards are WATERPROOF. Water will not pass through the board, unless you leave open gaps or puncture with fasteners.
If you seal the gaps and fastener holes with these - water cannot get through and cause unseen damage.

The negatives of these boards:
- require specific washers and fasteners.

The positives:

• Lightweight
• Very easy to cut
• No harmful dust (zero with Kerdi board)
• Very fast to install
• TOTALLY WATERPROOF when installed correctly
• Very strong and can take great amounts of weight

Hopefully for some not so familiar with these board-types this will help to show that using a cement board in a wet area is a total waste of your time and money.
Not only are you working with a difficult board, but you then need to tank them too.
If you use a waterproof board, not only are they far easier to work with, but you don't need to tank them either.

I install loads of wet rooms (and replace loads too) and I've learnt over the years that you MUST keep learnin.
Keep asking WHY as well as HOW. Go on the manufacturer's training days.

Any questions???

I'm building a concrete hot tub and thinking of using this as an insulator and tiling mosaic tiles directly on top, do you think if I do it right this is a sound plan? I'm in too minds.

 

[Joanne T]

It feels like there is a constant asking about the suitability of cement board in wet areas.
"Will they be ok in my wet room?" "Should I tank them?" etc etc etc
Can I attempt to clear up the confusion - much of which comes from the manufacturers and the builder's merchants who sell the stuff?

First of all: WATERPROOF vs WATER-RESISTANT
I honestly want to bang my head against a wall when this comes up.

1) Waterproof means water cannot get past the board.
2) Water-resistant means ONLY that water will not damage the board's integrity.
BUT - water can still soak through the board to the background.

Cement / Silica board - I class as Hardibacker / AquaPanel / NoMorePly
These are NOT WATERPROOF. They are sold as suitable for showers / wet areas etc and in my opinion they should not be sold as such. They are only "suitable" in as much as they won't get damaged by water - but unfortunately in my experience they will allow water to damage everything else - your tiling, your timbers and your rooms next to and below the one they're in!

The negatives of these boards:

• Heavy
• Difficult to cut
• Slow to install
• Contain silica dust (v harmful)
• NOT WATERPROOF - require tanking to make waterproof.

(note that tanking will reduce inherent weight-bearing though)

The positives:
- very strong and can take great amounts of weight

OK - Waterproof Boards now:
I class as Schluter's Kerdi board / Wedi board / Marmox board / Delta Board - there are others claiming the same properties but I can't vouch for them.
These boards are WATERPROOF. Water will not pass through the board, unless you leave open gaps or puncture with fasteners.
If you seal the gaps and fastener holes with these - water cannot get through and cause unseen damage.

The negatives of these boards:
- require specific washers and fasteners.

The positives:

• Lightweight
• Very easy to cut
• No harmful dust (zero with Kerdi board)
• Very fast to install
• TOTALLY WATERPROOF when installed correctly
• Very strong and can take great amounts of weight

Hopefully for some not so familiar with these board-types this will help to show that using a cement board in a wet area is a total waste of your time and money.
Not only are you working with a difficult board, but you then need to tank them too.
If you use a waterproof board, not only are they far easier to work with, but you don't need to tank them either.

I install loads of wet rooms (and replace loads too) and I've learnt over the years that you MUST keep learning.
Keep asking WHY as well as HOW. Go on the manufacturer's training days.

Any questions???

Finally, a post which explains things! I've been searching the internet for days. Thank you!
One question please. As you are talking about a wet room here, does the same apply to a bathroom, with only occasional splashes hitting the floor? My new bathroom has a bath and basin, and a walk- in shower (tray and glass screen both 1200mm long so not many splashes out of the open end) .

I am at the stage where I need to buy backer boards for my suspended bathroom floor, currently the subfloor is newly laid 18mm OSB3 boards screwed into joists and I want to tile it so i (apparently) need a backer board of some type in between.
Added complication is that my washing machine is also in the bathroom so (until I read this post!) I was thinking cement boards for the added strength and impact/noise reduction, as it's an upstairs bathroom and the spin cycle does obviously 'shimmy' the room to an extent so am worried what that would do to tiled floor and other waterproofed joins in various parts of room!

Would you, in this scenario use cement boards?
Or would you put 1 x 6mm cement board under washer, then use the 6mm foam-based/waterproof boards on the rest of the floor.
Or just the foam boards everywhere?
I would really appreciate some expert advice, thanks in advance

 

[Joanne T]

It feels like there is a constant asking about the suitability of cement board in wet areas.
"Will they be ok in my wet room?" "Should I tank them?" etc etc etc
Can I attempt to clear up the confusion - much of which comes from the manufacturers and the builder's merchants who sell the stuff?

First of all: WATERPROOF vs WATER-RESISTANT
I honestly want to bang my head against a wall when this comes up.

1) Waterproof means water cannot get past the board.
2) Water-resistant means ONLY that water will not damage the board's integrity.
BUT - water can still soak through the board to the background.

Cement / Silica board - I class as Hardibacker / AquaPanel / NoMorePly
These are NOT WATERPROOF. They are sold as suitable for showers / wet areas etc and in my opinion they should not be sold as such. They are only "suitable" in as much as they won't get damaged by water - but unfortunately in my experience they will allow water to damage everything else - your tiling, your timbers and your rooms next to and below the one they're in!

The negatives of these boards:

• Heavy
• Difficult to cut
• Slow to install
• Contain silica dust (v harmful)
• NOT WATERPROOF - require tanking to make waterproof.

(note that tanking will reduce inherent weight-bearing though)

The positives:
- very strong and can take great amounts of weight

OK - Waterproof Boards now:
I class as Schluter's Kerdi board / Wedi board / Marmox board / Delta Board - there are others claiming the same properties but I can't vouch for them.
These boards are WATERPROOF. Water will not pass through the board, unless you leave open gaps or puncture with fasteners.
If you seal the gaps and fastener holes with these - water cannot get through and cause unseen damage.

The negatives of these boards:
- require specific washers and fasteners.

The positives:

• Lightweight
• Very easy to cut
• No harmful dust (zero with Kerdi board)
• Very fast to install
• TOTALLY WATERPROOF when installed correctly
• Very strong and can take great amounts of weight

Hopefully for some not so familiar with these board-types this will help to show that using a cement board in a wet area is a total waste of your time and money.
Not only are you working with a difficult board, but you then need to tank them too.
If you use a waterproof board, not only are they far easier to work with, but you don't need to tank them either.

I install loads of wet rooms (and replace loads too) and I've learnt over the years that you MUST keep learning.
Keep asking WHY as well as HOW. Go on the manufacturer's training days.

Any questions???

Finally, a post which explains things! I've been searching the internet for days. Thank you!
One question please. As you are talking about a wet room here, does the same apply to a bathroom, with only occasional splashes hitting the floor? My new bathroom has a bath and basin, and a walk- in shower (tray and glass screen both 1200mm long so not many splashes out of the open end) .

I am at the stage where I need to buy backer boards for my suspended bathroom floor, currently the subfloor is newly laid 18mm OSB3 boards screwed into joists and I want to tile it so i (apparently) need a backer board of some type in between.
Added complication is that my washing machine is also in the bathroom so (until I read this post!) I was thinking cement boards for the added strength and impact/noise reduction, as it's an upstairs bathroom and the spin cycle does obviously 'shimmy' the room to an extent so am worried what that would do to tiled floor and other waterproofed joins in various parts of room!

Would you, in this scenario use cement boards?
Or would you put 1 x 6mm cement board under washer, then use the 6mm foam-based/waterproof boards on the rest of the floor.
Or just the foam boards everywhere?
I would really appreciate some expert advice, thanks in advance