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Hi All

I'm new to this site so apologise if this subject has been covered.

I am preparing to tile a bathroom floor which is conventional T&G floor boards in good and solid condition. I have always been under the impression that I would need to use 15-18mm WBP ply as a sub base for the tiles. I have recently been told that 6mm ply will be good enough but I don't want to under do it and end up with cracked tiles or grout.

What thickness ply would it be best to use? If I can use the 6mm then the height difference between the finished floor and the landing floor would be less and therefore easier to join up neatly but obviously not at the expense of doing it properly.

Thanks very much.

15mm is minimum as per British Standards. The reason for this is that 6mm will add hardly any strength to the floor or stop deflection, in addition 6mm ply is fairly unstable when in contact with moisture from the adhesive even more so with the cheap imported ply around at the moment.

I would avoid ply altogether and go for a tile backerboard, in your situation I would suggest a concrete board like 'No More Ply' you can use the 6mm boards but for floors I always go with the 9mm version on the tile backer boards

http://www.nomoreply.net/

Oh and ask whoever told you 6mm ply is fine if they will come and retile your floor when it cracks

You also have plastic ply available from Nicols and Clarke. I have used that a few times now and not had any problems or heard of anyone using it that has had trouble.

Ditra matting by schluter is also another very good product.

Both of these will keep the final finish level of the floor to a minimum.

Agree with Colour about the 6mm ply, the person who advised that needs shooting.

royaloakcarpentry wrote:You also have plastic ply available from Nicols and Clarke. I have used that a few times now and not had any problems or heard of anyone using it that has had trouble.

Ditra matting by schluter is also another very good product.

Both of these will keep the final finish level of the floor to a minimum.

Agree with Colour about the 6mm ply, the person who advised that needs shooting.

Hi ROC,

You're gonna hate me as it must seem as though I’m disagreeing with you all the time at the moment

I've never used plastic ply myself but I have seen a horror job done with it where it failed, after you've seen the pics I doubt you would want to use it again. I'm sure it might be a good product in some situations but conditions have to be right IMO.

Also Ditra is for lateral movement not deflection, so if there is any deflection which is normally the case with T&G then it will be of no help. Ditra is a great decoupling membrane as you say but not advised to strengthen T&G boards.

Sorry mate not trying to contradict you at the moment

id go with 6mm hardi everytime!

Colour Republic wrote:

royaloakcarpentry wrote:You also have plastic ply available from Nicols and Clarke. I have used that a few times now and not had any problems or heard of anyone using it that has had trouble.

Ditra matting by schluter is also another very good product.

Both of these will keep the final finish level of the floor to a minimum.

Agree with Colour about the 6mm ply, the person who advised that needs shooting.

Hi ROC,

You're gonna hate me as it must seem as though I’m disagreeing with you all the time at the moment

I've never used plastic ply myself but I have seen a horror job done with it where it failed, after you've seen the pics I doubt you would want to use it again. I'm sure it might be a good product in some situations but conditions have to be right IMO.

Also Ditra is for lateral movement not deflection, so if there is any deflection which is normally the case with T&G then it will be of no help. Ditra is a great decoupling membrane as you say but not advised to strengthen T&G boards.

Sorry mate not trying to contradict you at the moment

He hasn't mentions any problems with the floor being unstable, so that was why I advised on those as alternatives.

Whack the pics on of the plastic ply, Rogues gallery would be a good place..............Iv'e never had a problem with it, so hopefully the horror story is because the fitter did something wrong.

This old chestnut 6mm ply is a no no, always has been, well for as long as i've been a tiler 23 years, these days Ditra schluter as an uncoupling membrane, which may i add, i have used for many years and have had many a discussion with the schluter rep , is perfect for 99% of applications, or Knauf aquapanel for extra rigidity if in doubt, 1" ply is good if replacing existing floor t&G / boards, and yeah i've heard of the plastic ply problems from a couple of tilers.

Thanks for the replies. I didn't think 6mm ply was up to the job but the chap who still swears by it is a pro tiler who I asked to quote me for the work due to having recently broken a leg and not being very mobile.

I've been and looked at all the products that have been recommended and I think I'll take all the advice on board and do it myself.

Thanks again.