Backerboard or Ditra on Plywood?

[hammerandnails]

Hi everyone,

I'm having the majority of the ground floor of my house tiled (35m²) and I'm not sure which way to go from a subfloor / prep perspective. Here is the current set-up:

• Suspended timber floor at 450mm centres
• Wet underfloor heating system between joists in a pug screed
• Tiny bit of deflection (<3mm) in one corner of the room which will be covered by kitchen units anyway
• Large (~600x900mm) porcelain tiles to be the finished floor

Based on cost, floor build-up, ease of installation etc. I've narrowed it down to two options, and would really appreciate anyone's advice on which one to go for (or something entirely separate!):

Option 1: 18mm t+g wisa sprucefloor plywood on joists > 6mm backerboard > tile
Option 2: 22mm t+g wise sprucefloor plywood on joists > ditra mat or dura base > tile
(plywood will be sealed on both sides before installation)
Option 3: Knauf gifa floor instead of plywood - way too expensive and don't like that it is a floating floor rather than mechanically fixed.

I'd prefer the option with the lowest floor build-up, and the best structural stability - so here, option 2 wins. I'd also prefer to be doing as little screwing as possible into a floor with underfloor heating pipes in it! However, I've heard mixed opinions on using ditra/dura matting on plywood so would appreciate your input.

What does everyone think??

 

[demi34]

Option 1 for me because i is the right one

 

[hammerandnails]

Option 1 for me because i is the right one

OK thanks - is there a reason why you'd avoid the other option in particular?

 

[demi34]

OK thanks - is there a reason why you'd avoid the other option in particular?

Because ditra will not stick same way as hardiebaker boar.

 

[Ben-gee]

I wouldn’t use 18 mm ply on 450 centres, bouncy bouncy.

 

[hammerandnails]

Because ditra will not stick same way as hardiebaker boar.

In that case, if I go with backerboard, can I used normal 22mm chipboard rather than ply? It's considerably cheaper. Or is that not ideal for use with wet UFH?