How many noggins between joists when replacing floor boards

[Lower]

.....with 25mm wbp ply.

I'm soon to be laying a travertine tiled floor in my bathroom and have just got the existing ply and vinyl tiles up.

The floor boards are in a right state, so rather than repair them and then overboard with 18mm ply i've decided to rip them up and just replace them with 25mm ply.

Reading the FAQ its says that i need to add noggins between the joists to support the ply, but how many?Obviously i need noggins at the joins in the ply and the joists are spaced at roughly 14" so what sort of spacing do i need for the noggins? The room is fairly small, approx 8 foot square.

Thanks in advance.

 

[Symptoms]

Lower - smallish joist lengths skinned with screwed down 25mm ply not critical to install nogs, apart from below any joins in the ply (as you realise). However, seeing that the existing floor covering is coming up and you are proposing to lay expensive tiles, it won't harm the installation to whack-in some nogs to 'tighten-up' the structure (maybe 3 per length). It'll hardy cost you anything for the timber and screws (yes, screw the nogs in don't nail). By doing this you'll minimise any bounce/movement in the floor thus reducing the risk (IMO to zero) of damage to the tiles.

Try to get full sheets of ply down 2off 8 x4 rather than smaller boards although it may be difficult 'cos of space & weight.

 

[Lower]

Thank you for your help.

3 Noggins per set of joists (screwed) is quite straightforward. The room is actually slightly smaller than i specified, 7ft x 7ft, so i can use two 8x4 sheets fairly easily.

With that much support it certainly should be a proper job!