replacing floor boards

[FreeD]

Started a new job today 2 bathroom floors with old floorboards which have been lifted up on and off over the years for plumbing/electrics etc...i did the bounce test and noticed flex in the boards so proceded to secure them with goldscrews to the joists...unfortunately some of the boards were in such a bad state i've had to completely replace them...the only floorboards i could find were slightly narrower and slightly thinner...the timber merchant said something about the old boards being imperial measurements and that i wouldn't be able to get hold of same size...anyway i've fitted the new boards in now width is ok but in some places the boards look about 5mm thinner than the other boards...2 questions

will it be ok to ply over all floorboards with 12mm ply now despite some of them being slightly thinner?

if i were to use 18mm ply in future is there really a need for the floorboards to be secure before overboarding?...considering 18mm ply should strengthen the floor

[doug boardley]

would it've been possible to take the floorboards out altogether and use a 22mm ply or hardie backer in this case?

[FreeD]

thought of that but can't hit the joists at edge of room as the bathroom was previously split into 2 and the last joist isn't accessible.

[mikethetile]

5mm is abig difference you can usually get metric closer to imperial than that, you can over board but theres a danger that when you screw down you will end up with an uneven floor

you can make up the difference by cutting hardboard the width of the lower boards and tacking down, hardboard comes in 4mm width , tack smoothside down

[grumpygrouter]

[quote=FreeD;173181]Started a new job today 2 bathroom floors with old floorboards which have been lifted up on and off over the years for plumbing/electrics etc...i did the bounce test and noticed flex in the boards so proceded to secure them with goldscrews to the joists...unfortunately some of the boards were in such a bad state i've had to completely replace them...the only floorboards i could find were slightly narrower and slightly thinner...the timber merchant said something about the old boards being imperial measurements and that i wouldn't be able to get hold of same size...anyway i've fitted the new boards in now width is ok but in some places the boards look about 5mm thinner than the other boards...2 questions

will it be ok to ply over all floorboards with 12mm ply now despite some of them being slightly thinner?

if i were to use 18mm ply in future is there really a need for the floorboards to be secure before overboarding?...considering 18mm ply should strengthen the floor[/quote]

When you screw ply down you are screwing to the boards. If the boards are not secure first your ply is not secure!

[brian c]

5mm is abig difference you can usually get metric closer to imperial than that, you can over board but theres a danger that when you screw down you will end up with an uneven floor

you can make up the difference by cutting hardboard the width of the lower boards and tacking down, hardboard comes in 4mm width , tack smoothside down

then you would need to overboard with a minimum 9mm ply as the adhesive wont have a secure bonding to the hardboard.Personally i wouldnt use hardboard anywhere near a tile installation.

[david campbell]

think the hardboard is sitting on top of the floorboards to stop the gaps between floorboards and ply,basically taking out the void between floorboards and ply,so it wouldn't come into contact with tililng!