DIY Doctor UK DIY Forums

I have stripped my kitchen floor back to a concrete slab covered with pitch about 75mm below the original finished floor level.
I intend to cover this with 50mm kingspan insulation, lay a floating floor and then tile.
What would you recommend for the floating floor?
I am worried that if I use P5 chipboard something like the washing machine flooding will make it swell.
Should I cover the chipboard with plywood?
Should I use plywood instead of Chipboard?
if I use Plywood it is not tongued and grooved so should I use 2 layers offset then screwed together?
I am not too worried about the thickness within reason.
Any other suggestions?

marine ply would be the absolute best thing if you want a water proof solution (pardon the pun)

im not absolutely familiar with the project you are doing, but it seems to me you have two choices.

1. Either use marine ply, this is much more water resistant (though not water proof) than normal ply and ALOT more than chip or MDF. and as a bonus is also much much stronger. though very expensive

2. use chip board and coat it with a water proofing paint, or coat with water proofing material. this is going to be alot of effort it would be water proof so long as you do a good job of coating it.

i think if you plan on putting down a floor such as quarry tiles or stone flooring then you wouldn't need the water proofing, yes a little would seep through the joints but unless you left it there for a while it would dry up itself.


oh and on the note of joining, yes 2 layer offset and screwed is good, but you could also consider using a seeler between them, (halves the cost of the ply :)

hope that helps a little, im no expert just a DIYer