Attaching ply to floor?

[1pudding1]

Im putting a new vinyl floor in my bathroom. I have bought some sheets of 9mm plyboard to put down as the underlay. The floor is concrete/screed.

How do I attach the ply to the floor, as if just lay it down, there is a small amount of flexing and bending in certain areas from a tiny ridge in the concrete. Do I simply use some screws into the concrete, or are they nails/glue etc to use for this job?

Thanks.

 

[Symptoms]

pudding - consider using a self-levelling compound over your concrete/screed to produce a smooth surface for your vinyl. This is poured and quickly trowelled over and left to set (quite easy to do). The vinyl is layed directly onto this. Don't use the ply.

 

[1pudding1]

Id quite like to use the plywood, as I already have it, and it will raise the floor a little so that the vinyl tiles will bit snugly under the existing skirting boards. Unless its a really bad idea to attach these plyboards to the concrete for some reason?

Here a couple of pics of the offending square area in the corner that is slightly higher than the rest of the floor, and a couple that shower the gap the ridge causes on each side . If I were to use a levelling compound, im worried that the height of the compound would be quite high if the whole floor was brought up to the height of the ridge.

Will simple masonry nails do the trick to secure the wood to the concrete?

 

[chippyphil]

Trying to secure ply to the floor would likely end up in serious frustration

The ply wouldn't help with the lumps and bumps really, and would end up with voids where the low points are.

Masonry nails are not likely to even make a dent in the concrete!

The only sure-fire way of getting a good surface is as mentioned above, using self levelling latex.

If you really want to put ply down, I would suggest the latex first followed by a moisture proof barrier (either a paint on or a plastic DPM - with blobs of building adhesive) Then I would cut the ply in and stick it down with a building adhesive too (gripfill, sticks like sh!t etc)

A waterproof barrier will prevent condensation forming on the underside of the ply, unless of course, you have underfloor heating. In that case it won't be necessary.

HTH

 

[1pudding1]

Ok thanks. Where from and whats the best type of latex levelling compound to use then?

Also, when I took the old laminate floor up in there, there was the sheet of plastic dpm under it, so I assume there is nothing currently in the floor without it. Is latex compound ok to pour straight on the concrete, or should it go on top of the plastic sheet?

 

[Symptoms]

pudding - after looking at your pics I reinforce my view that you should use self-levelling compound only. Loads of advice to answer your questions in the Sticky section above - How to use self-levelling compound.

 

[mattysupra]

as symptons has suggested, levelling compound and read the sticky. Also use acrylic based not latex!