Tiles Cracked On All Hardiebacker Joins

[Bathfix Bob]

I tiled an L shape bathroom floor 5 months ago and long cracks have appeared at 800mm centres striaght over the Hardiebacker joins.

I've never had any cracks through tiles since 6 years ago when i used to tile on 12mm ply.

The tiles are 300mm British ceramic.

House was built 1984, standard 18mm floorboards which I securely screwed down, deflection free.
Hardiebacker was laid onto rapidset flexible addy (Larson) and staggered over floorboards, I always end Hardie half way along a floorboard.

Screwed down fully including extra screws on the edges and then tiled with Ultra fast set.
Its a method that has never failed in 6 years apart from this floor.
The only thing is up to now I've just been taping and filling the joins with plasterboard scrim tape, but I'm going to switch to the thicker type after this.

Cannot work out why this floor should fail and all the others havent, there are no leaks anywhere, no RSJ underneath, no recent work.

 

[Rich Midge]

Ultra Pro Flex or Pro Rapid? I know a couple of tilers who have used the pro rapid over boards and had problems even though it states it'll go over over boarded floors.

 

[Dave]

Did you use hardi tape on the board joints and leave a gap between each board. ?

 

[Time's Ran Out]

It's the tiles!
30x30 British ceramic that state they are suitable for no shoe floors!!
They are a soft glaze/wall tile biscuit that IMHO should not be used on floors.
Even if there is no movement in the floor ( and in this case there must be a small amount) they will crack on these seams. I'd insist I would only fix these over Ditra in a bathroom.
Unless you got a disclaimer it's still your fault.

 

[macten]

Agreed - even without tape there's no way that should happen, got to be the tiles.

 

[Stef]

I'm with TJ, I have fitted these tiles & I even phoned CTD & the manufacturer to double check they are suitable for floors as in my option they aren't, they are far too soft.

 

[Spud]

I have had similar problems in the past with hardi , 2 different floors first one was 12mm hardi over floor boards stuck with rapid and screwed down then ufh cable latexed in with fibre reinforced latex the tiles were also ceramic and cracked through the hardi joints ,mit remedied it by lifting the tiles then put Ditra over the sub floor which was sound but had suffered shrinkage , there was a small leak from the shower seal but not enough to cause the problem I saw,
My guess was the water from the adhesive under the hardi and the water from the latex was absorbed by the hardi and which swelled up the tiles were fitted too soon over the floor as the floor dried the hardi shrunk back and caused the cracking
Second one
12 mm hardi over floor boards stuck with rapid and screwed down with turbo gold screws scrim tape then tiled with rapid floor dropped away about 6mm which was picked up with adhesive cheap ceramic floor tiles and a few cracked
My solution now is to seal hardi both side before fitting with SBR as I believe it swells then shrinks from the water content and use anti fracture matting on softer tiles like ceramic or encaustic

 

[John Benton]

From the Hardibacker Website

What is Cement Backerboard?

HardieBacker® is a cement backerboard for tile and stone to be used as a replacement for plasterboard or plywood. It contains MouldblockTM Technology, giving you superior moisture and mould resistance. HardieBacker® provides a dimensionally stable cement bonding surface that won’t warp, swell, rot, or deteriorate even in the wettest conditions. It is available in 6mm and 12mm sheets and provides the best bonding surface for cement based tile adhesive. HardieBacker® 6mm with EZ Grid® has a recessed fastening pattern to make installation even easier. HardieBacker® is the #1 cement board in the world.

 

[Stef]

The Americans hate Hardie for some reason & I've seen posts of people reckoning the same as Gary that it's absorbed moisture.

 

[John Benton]

I had one in a very small en-suite, only 2.5m tiled floor area, one the the tiles had a straight hairline crack across it, lifted the tile and it wasn't even on a joint, the 6mm board had just just a fine crack that had transferred through the tile. No other problems just that one tile. Very strange.

 

[Stef]

That is a strange one John.
I've still to go look at a floor that has a hairline crack in it.
Hardie fitted (not by me) then got informed it was getting a heat mat, I fitted this & slc.
Then they told me marble was being fitted, I told them to decouple but they wouldn't pay the extra for it & now there is a crack running the length of the bathroom.

 

[John Benton]

That is a strange one John.
I've still to go look at a floor that has a hairline crack in it.
Hardie fitted (not by me) then got informed it was getting a heat mat, I fitted this & slc.
Then they told me marble was being fitted, I told them to decouple but they wouldn't pay the extra for it & now there is a crack running the length of the bathroom.

Didn't investigate it any further other than replacing tile and that was a while ago and not heard anything back. No idea to this day how it got a crack in the middle of a board that only affected one tile

 

[Bathfix Bob]

Thanks for the replies guys, the floor was solid, with my floors I probably spend 70% of the time with the prep. Every floorboard screwed down with 50mm screws.

Since this I've started using the proper harie tape rather than plasterboard tape, there were 3mm gaps between the boards.

 

[Stef]

Thanks for the replies guys, the floor was solid, with my floors I probably spend 70% of the time with the prep. Every floorboard screwed down with 50mm screws.

Since this I've started using the proper harie tape rather than plasterboard tape, there were 3mm gaps between the boards.

I don't think you done anything wrong, I still think it's the tile.
Do you know the tile name or have pictures of them?
As I said I've used these "Floor" tiles & they aren't suitable for their intended use.

 

[John Benton]

I don't think you done anything wrong, I still think it's the tile.
Do you know the tile name or have pictures of them?
As I said I've used these "Floor" tiles & they aren't suitable for their intended use.

I fitted some of these ceramic tiles and before I did, the first thing I did after seeing them was read the box, that confirmed they were suitable for the floor, and then I rang the supplier to make sure they are happy that they would be fixed to a floor. Thirdly I did stress to the customer that they could fail and that I would not be held responsible. I did take photos all the way through the floor fixing installation as proof that they had a solid bed and tiles were back buttered. They haven't failed, yet!!!