New floorboards or plywood?

[iwilson16]

Im planning on replacing the old split/broken/warped floorboards (approx 25mm thick) in a bedroom 3.6x4.5m) with either 32x150mm (28x137mm finished) PTG white wood floorboards, 18mm ply (shimmed up to 25mm), or 25mm ply.

Floor joists are 457mm centres, and 83mm wide.

I can't decide which to use. Ply has the advantage of being able to easily lift sections in the future if I need access to wires or pipes.

25mm ply is expensive and heavy ... I'd need to get the timber merchant to cut the 12x8 sheets in two longwise before delivery. It's stiff enough that it wouldn't need noggins to support the long edge.

18mm ply would be cheaper and easier to handle, but might it flex on the long edge between joists?

Should I leave a gap (1-2mm?) between the long edges of ply, and fill it with a flexible mastic?

Would the floorboards need acclimatised in the room for a while before fitting? Is there a risk they will bow?

I plan to carpet this room at some point.

Thanks,
Ian

 

[motorbiking]

why aren't you looking at a proper t&g P5 structural chipboard?

do you know how far apart your joist are? 18mm should be good for up to 400mm spacing.

 

[iwilson16]

Yes, I might do that. What product do I look for in the builders merchants? One reason I was using plywood was because I want to keep a section of floor that I can easily lift if necessary as it has a load of services underneath. I guess I could use 18mm ply for thy section, plus extra noggins for the unsupported edges.

Floor joist centres are 82mm wide with 457mm centres.

Ian

 

[motorbiking]

18mm is suitable for 400mm joist spacing 22mm is suitable for 600mm spacing..

http://www.championtimber.com/sheet...m-t-amp-g-flooring-chipboard-mr-p5-fsc-mix-70

If you want a liftable section I'd just cut the tongue off on that board. I'd also mark on the position of any pipes/services as the boards go down its amazing how quickly you forget and it only take one screw.

If you lay in a brick pattern ,it will be stronger than 2.4 by 1.2 ply as you'll have overlapped joins