Porcelain Plywood + Flexible adhesive or Plywood + Ditra matting

[Marty M]

Hi there, need some advice. Have spoken to quite a few tilers, tile companies and read loads of info online and now I have a lot of conflicting advice/mixed opinions.

I am renovating a house and have a 4m x 10m kitchen area. Original kitchen and flooring has been removed leaving a large empty space. The floor at the minute is simply floor boards. These are on top of wooden joists as there is no concrete base below except at foundation level.

I am getting the floor tiled and this is where i have got a lot of different opinions on how this should be done. Initially the plan was to plywood the area on top of the floor boards and then tile on top of that with flexible adhesive. Tiles = 60cm x 60cm

One tile company then recommended the Ditra matting which no one else did (the others i guess either assumed i was using it or thought that the plywood would suffice). What has made me look into the Ditra matting is that the company said not a lot of people use it because of the extra expense but in their opinion I "would be mad" not use it on that size of area to be tiled.

Therefore I am trying to seek advice from people on the forum of what I should do. The expense of the Ditra matting isn't a major issue but like most people I don't want to waste money if I don't need it. The biggest thing for me is that the job is done right to reduce the risk of cracked tiles etc as much as possible as the renovation is costing a whole load of ££££ and so i want to make sure it is done right from the very start.

 

[Old Mod]

Couple of things first before deciding best course of action.
Is the floor heated?
The way I read it, is that it’s a suspended floor, is that correct?
What material are the floor tiles, are they porcelain?
And the most imortant thing, to prevent cracking tiles, is there any deflection (bounce) in the floor?

 

[Marty M]

Thanks 3_fall for replying. No there is no underfloor heating, yes it is a suspended floor and the tiles are porcelain. Regards to deflection, the plywood layer is not installed yet but it will be heavily screwed down in order to minimise deflection.

 

[Old Mod]

There are several approaches you could take.
By far the best is to remove floorboards and install either GIFA board from Knauff,
Or 22mm No More Ply
Both are structural and inert materials. (Not effected by temp or moisture).

Personally if Ply was used I’d want one 12mm layer, (broken bond) screwed to joist.
Then cover with wood glue and put a second layer of 12mm over the top, again broken bond but also perpendicular to the first and ONLY screwed in to first layer, and not joist. Then use an anti fracture mat over the top, they’re similar to Ditra but are more specificly to deal with lateral movement, whereas Ditra has more functions, hence the higher price.

 

[Old Mod]

Second layer of ply screwed EVERY 200mm.

 

[Marty M]

Thanks for the info. Problem I now have your advise is that it is advise that i have not yet had elsewhere or have looked at so another curve ball in my decision making process. Taking your advise and slightly modifying it to avoid removing the floor boards... is the below an option?

• Plywood on top of floor boards using wood glue and screwed as per recommendations to minimise deflection.
• Layer of anti fracture mat over the top of plywood.
• Tiles on top of anti fracture mat using flexible adhesive.

 

[Old Mod]

If you’re leaving floorboards down, then overboard with a cement board or insulation board, not Ply, then a mat.
Just noticed where you are, @LEE MAC may be in a better position to suggest appropriate materials in your area, as I know they can be limited.

 

[Marty M]

Thanks for that.. For kitchen areas, is ply wooding now a thing of the past i.e. cement/installation boards now a better technique? Everywhere I read seems to mention plywood and/or external plywood which would be more resistant to changes in temp etc as a substrate layer

 

[Boggs]

Only timber floor I have ever had a failure on was floorboards over layed with 6mm Hardie.
You end up with basically 3 joints in around 5 inches and that’s where the tiles cracked.
I always take them up now.

 

[Unused Account 1]

Main thing ensure al floor boards are secured first ,then ply ,i did a job similar,the joinerpulled up the boards ,then 18 mm ply onto joists ,then ditra ,big area do it once properly ,

 

[Dumbo]

Main thing ensure al floor boards are secured first ,then ply ,i did a job similar,the joinerpulled up the boards ,then 18 mm ply onto joists ,then ditra ,big area do it once properly ,

If you do as @3_fall you do not at any point get a continuous joint coming from the joists to the to surface

 

[Marty M]

Only timber floor I have ever had a failure on was floorboards over layed with 6mm Hardie.
You end up with basically 3 joints in around 5 inches and that’s where the tiles cracked.
I always take them up now.

Thanks for the reply @Boggs . Yes I was told the substrate floor needs to be a decent thickness. 6mm defo too thin

 

[Marty M]

Main thing ensure al floor boards are secured first ,then ply ,i did a job similar,the joinerpulled up the boards ,then 18 mm ply onto joists ,then ditra ,big area do it once properly ,

Cheers for the reply. I now have two people on here, yourself and 3_fall who have recommended pulling up the floor boards. Looks like this is the way to go. Regards to the Ditra, any particular brand/type of adhesive you use for the Ditra to ply and then tile to Ditra?

 

[Andy Rhodes]

I'd use 12 mm Hardiebacker board over top of your floorboards but ensure that the floorboard aren't loose or rocking then screw backer board every 150 mm or 6 inch in old money if you want to be over cautious screw 10 mm centres use yellow zinc screw though as they don't corrode apparently