Plywood advice

greggp_2

I am re-doing a en-suite and am sorting out flooring at the moment. I currently have a T&G chipboard floor nailed on joists. Karndean recommend installing a Plywood to comply with warranty of product and I was going to do this anyway because of it being a wet area.

I am therefore going to lay a WBP plywood floor on top of this but was wondering what thickness would be best? I would prefer 6mm as this wouldn’t hinder my current floor level too much but having looked at B&Q this afternoon this does seem somewhat flimsy and wondered if it may be beneficial to go for a 9mm or 18mm thick plywood instead?

I have a bit of movement in the chipboard T&G boards currently which I am going to look at securing – If I was to opt and secure a thicker Plywood say 9mm or 18mm and screw through joists I feel that this may eliminate any movement below, obviously I will try and eliminate any movement as best I can in the chipboard prior to commencing with anything.

DirectDebacle

Lots of ways to do this. Buy the thickness of ply Karndean specify to comply with the warranty and work around that.

As an example if they specify minimum thickness of say 12mm and the karndean is 3mm would a 15mm step be too great? If so consider removing existing chipboard say 21mm thick and replace with 18mm ply then karndean will finish flush with existing floor. Or use 21mm ply (9mm on top of 12mm) then kardean etc.

har0ld

I try to remove chipboard from wet areas completely - as I think it completely inappropriate.

I also like to lift the old floor to get an idea of the horrors lurking beneath!

I then lay 22mm ply (external grade shuttering is fine) and I can carefully screw down the floor to joists etc knowing that there will be no more creaky floor and I can put anything I like on top tiles, karndean whatever.

Unless you have a trade card for B&Q, go to your local timber yard or trade-builders merchant; and get the ply for a fraction of the price with usually far better service!

stuyat10

As a past Karndean fitter for 10 years - I would recommend you go for Minimum 9mm ply -12mm Ideally. The reason for this is - the thicker the Ply, the less flex it has, thus giving you a more level surface. You would need to secure any of the chipboard T&G underneath and I always used to screw the ply down instead on nailing with arringular nails. If you do screw the ply down then make sure you fill the screw heads with a filler. The correct way is to use a 'feather finish' (a flexible screed for use of wood) over the boards, prior to laying the Karndean. This is because Karndean glue is very powerful stuff once cured and it some cases can show head marks through the material in certain lights...

Hintza

Our architect specified pine planks for the bathroom and forced the builders to remove the chipboard which they had tried to get away with. We then had 6mm ply popped on top and nailed every 2 inches.

Your decision will really be decied by the levels but 6mm should be fine with a decent base.

Just as an aside our chicken coop (old pheasant rearing shed) was made of 6mm ply and was surprsingly good (until he storm in May blew it away )

greggp_2

stuyat10 wrote: »

As a past Karndean fitter for 10 years - I would recommend you go for Minimum 9mm ply -12mm Ideally. The reason for this is - the thicker the Ply, the less flex it has, thus giving you a more level surface. You would need to secure any of the chipboard T&G underneath and I always used to screw the ply down instead on nailing with arringular nails. If you do screw the ply down then make sure you fill the screw heads with a filler. The correct way is to use a 'feather finish' (a flexible screed for use of wood) over the boards, prior to laying the Karndean. This is because Karndean glue is very powerful stuff once cured and it some cases can show head marks through the material in certain lights...

Thanks for your post....I'm going to lay 9mm ply at the weekend. Would you recommend filling the joints between ply - I am going to lay larger sheets in whole as best I can with minimum joints but there are obviously going to be some. Are there any suitable compounds I could use please?