Once and for all (hopefully!) CEMENT Boards Explained

[One Day]

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???

 

[Old Mod]

Any questions???

Whose going to win the snooker masters, will Ronnie retain his title?
........so many questions!

 

[Dan]

stickyd the thread.
Kudos to impish.

 

[LM]

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

Excellent post Imp, very informative and helpful.

In my humble opinion the best system out there from my experience is Kerdi, for me it's second to none, Schluter have it nailed so to speak!

Just a point to note though, Ardex tell me that their WPC's weight bearing limit is the same as the substrates, what ever that may be?

 

[One Day]

Totally agree Lee. Kerdi is the best so far. I use it wherever i can. Still a pain to actually purchase still though!
I know ardex claim no effect on weight bearing but I'm not totally convinced. You seen the demo rig hardibacker have used where they hang a concrete slab off the board? I'd like to see the same board with ardex wpc on it!
Still, ardex wpc is my tanking kit of choice for plasterboard anyway.

 

[Stepneysteve]

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???

Hi Impish, Quality post mate, just starting out and soaking any info from experienced guys like a sponge, Love this forum!! Regards
Steve

 

[Qwerty]

Well done that man! Great post

 

[One Day]

Now this is just typically weird. I'm halfway through tiling a large floor, today the homeowner asked me to look at two bathrooms currently being prepped by their builder. Guess what they were literally just about to board the walls with?
Aqua panel.
Now changed to Wedi board.
I think the builder wanted to hit me!

 

[smokie899]

So just to clarify, board out with hardibacker, tank with gloss paint and prime with pva, is the best way forward. May I recomend on top of that to always use tubbed adhesive with the dot and dab method, ditch the tile spacers to save money and time, which also means you won't need any grout. And silicone is so over rated, so if you just make sure the tiles are butted to the bath/shower tray or each other tile as tight as possible, you won't need silicone
On a serious note...
Excellent post sir.

 

[John Benton]

stickyd the thread.
Kudos to impish.

Shower screen or tray

 

[widler]

I don't have a clue why anybody would use hardie or nmp on walls , its rubbish to use, ideal for floors imo but walls id rather use pb and tank

 

[Old Mod]

.
I think the builder wanted to hit me!

Mark sometimes I want to hit you, and I don't even know you!

I might add that this post includes some levity!

 

[One Day]

I have that effect on people!

 

[wau5]

The funny thing is, when you go and ask this on other forums you will get told that you NEED to use hardiebecker/cementboard to make it waterproof for wetrooms, I bought a couple of sheets of it as a test when Making my wetroom, I had my doubts when I took it home about its waterproof ability, so I tested it, and yup, It's not waterproof as You are made to believe!
I used it to add strength to kerb/niches and for a section of a wall and that's all where I used it, for the rest of the places I used PB , but I did go nuts with tanking everything properly (3-5coats).

Can't really believe everything someone says...

 

[Flintstone]

You don't need to go 'nuts' with the tanking, just what the manufacturer states, usually 2 coats

 

[Colour Republic]

I agree with a lot of that impish but there are times you might want a solid style cement board over and above a foam cored version.

Especially on floors

Solid cement boards are by their nature stronger and stiffer so can be used to rectify small amounts of deflection where as you may have to strengthen the subfloor first if using foam cored boards.

Also point loading. Foam cored boards do have a minimum tile size suitable, so a mosaic floor could be out of the question unless going for a solid cement board.

So there are a few more 'positives' with solid cement boards than just the sheer weight they can carry.

But like I say, agree with most points you mention.

 

[One Day]

20mm mosaics are ok on Wedi (although I would only do that in a bare-foot area myself)
but I take your point - I do occasionally use cement board on floors!

 

[average]

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???

Nomoreply is waterproof.

 

[One Day]

Nomoreply is waterproof.

Are you sure about that?!
Please back up your statement?

 

[Dan]

This says water "resistant" No More Ply Boards available from Tile Giant - http://www.tilegiant.co.uk/tools-accessories/no-more-ply.html

Bit misleading really.

 

[One Day]

Definition of IMPERVIOUS - https://www.merriam-webster.com/dictionary/impervious

I guess they are picking definition no.2 because no.1 sure as heck doesn't apply.

I have a bath sponge which is also impervious to water.

 

[One Day]

Nomoreply is waterproof.

This kind of statement really proves my point though doesn't it?!

 

[Old Mod]

Iv'e dug a little deeper @Dan
Like you've shown, first thing they say.


The word impervious, depends on the context.
Read definition 2.




And to waterproof completely, by definition has to mean they're not.

 

[Old Mod]

I guess they are picking definition no.2 because no.1 sure as heck doesn't apply.

Snap

 

[Dan]

G'wan lad.

 

[average]

This kind of statement really proves my point though doesn't it?!

Its what Ive been getting told from tike stores from day 1 I started using it.

 

[One Day]

Its what Ive been getting told from tike stores from day 1 I started using it.

And that's the point of this thread! They don't know or they lie, or the manufacturer misleads them.

 

[Flintstone]

I don't believe that two coats of sbr is going to water proof anything!

 

[One Day]

I don't believe that two coats of sbr is going to water proof anything!

I think a decent SBR would actually form a waterproof layer, but it would be very weak mechanically.
The act of troweling on it would compromise it immediately.

 

[Flintstone]

That's what I mean, it's not a propper water proof system, might stop a splash but that's about it