Ropey builders - Tile Advice

[Chippy Tarker]

Hi
I hope someone can advise please?
In Brief:
New extension with shower tray already down by builders. Timber joists with 18 mm chipboard floor, they have not glued the T&G joints or glued down.
I have put more screws in (Spax flooring screws) & used dowels and gorilla glue to get some glue between underside of chipboard and joist.
I have noticed that all joists are 400 centres with the exception of 1 spacing which is 450 mm.
Should I be concerned at the 450 centre bit and what process is best ready for floor tiling please?
I favour 6 mm Hardi adhesive and screwed down. Will this be strong enough?
Tiles are 600 x 600 x 10 mm porcelain
Many thanks in advance
Chippy

 

[Bond]

18mm chipboard at 400 centeres is about right, provided the joists are well supported and there is no bounce/deflection in the floor. It’s okay to use 6mm hardibacker or an uncoupling membrane such as ditra 25. Or similar.

 

[Chippy Tarker]

That's great, appreciate your time.
Just to add they are nearly all 400 centres with 1 gap being greater at 450 and this was my particular concern. Would it cause any problems?

 

[Bond]

The one joist spacing at 450mm is unlikely to give problems, especially as you have already glued and screwed the flooring.

 

[Chippy Tarker]

Many thanks for the advice