Cement board over floor boards with gaps?

[2020Tiling]

Hi ,
Just a question am unsure of and need advice with.
I need to over board some old floor boards in a bathroom ready for stone tiles to be layed. The floor is solid with no deflection but the floor boards have gaps in them and i am unsure how the spf would work when laying cement boards with the gaps ? Is it best to over board with 6mm ply first them SPF and fit Hardy Cement board on top of the 6mm ply? or is there another way? Also is it a must to install a crack mat with this installation?

 

[DHTiling]

The adhesive is to take up undulations in the substrate to create a solid fix underneath.. a few gaps in the boards will be fine if not like an inch wide or summit.. it is a must though to have a solid floor beforehand.

 

[Martyn Leeds]

Gaps?
as in just a couple of mm between each row of floor boards, or gaps where they've been hacked at by the plumber, or been damaged in the past?
Always make sure the floorboards are totally secure 1st.
And replace any week/dodgy boards as well

 

[2020Tiling]

Gaps are around 2/3mm and have not been tampered with,its the way they have all been layed. Just thought the SPF would fall through the gaps and leave a void! They also have varnish on so don't know if the SPF would bond well with the floor boards?

 

[DHTiling]

That size is ok and the adhesive is to fill voids .. the screws do the holding down.

 

[Time's Ran Out]

To add - I'd always use a decoupling membrane for Stone.