www.ultimatehandyman.co.uk

Small bathroom, 1900 X 1700, floorboards removed and being replaced by 18mm wbp ply (this thickness only).

This will be tiled, should I put noggins under where boards meet? Have done in larger span rooms but not sure about a small one?

Yes. you also need to deal with any flex issues. 25mm would be better. seal the back and all edges of the ply and make sure it is a quality one and not the cheap 5hit from diy stores or cheap timber/builder yards.

Thanks, will nog up the key areas. Hopefully have enough offcuts saved to get this rock solid.