Decouple / backer boards - Tile Advice

[Old_Brown]

So I have successfully done tiling before, but not over old floorboards on an upper floor. There are two areas and two bathrooms to do. One is new build and has standard new board flooring, the other has thin wooden T&G boards. Previously on new large board floors I used No More Ply, but one tile developed a stress crack. So --- should I use No More Ply (or similar) AND a decoupler in BOTH areas? If that's a yes - there are a wide variety of decouple membranes on sale. What would be the best choice. I'd be using 600mm square tiles (probably) and favour mapie adhesives and grouts for reliability.
Thanks in advance.

 

[Dave]

When you did the floors before , did you use the strengthening tape on the board joints

 

[Old_Brown]

I did use the tape yes, installed to the letter of NMP recommendations

 

[Dave]

I did use the tape yes, installed to the letter of NMP recommendations

Ok just checking as to why it cracked.
I prefer hardibacker tbh and not had any issues.
If you want belt and braces ( OTT prep) then crack matting can be used as well.

 

[Old_Brown]

any recommendations for matting? because I am amateur I tend to fix on one product that works for me and stick to that rather than fuss about ...

 

[Dave]

I always use Ditra. Few pounds extra but worth it.

 

[parkerfresh]

As mentioned, for belt and braces I would acrylic prime the floor and opt for 6mm hardie board glued and screwed, then Ditra matting fixed with either Ardex AF200 or a flexible powder gear on thin bed, squish it down with a grout float or use a proper weighted roller, then gear the floor up with a 12mm notch trowel and back butter the tile for full bed adhesion.

If the floor is solid, as in no up and down movement whatsoever, you can omit the hardie and just go straight on with AF200 & Ditra, providing the floor is flat, clean and primed.