Acrylic or Latex based screed?

[Graeme]

Hi

I'm going to level an old chipboard bathroom floor prior to fitting vinyl tiles. The existing floor is sound but quite uneven. My plan was to use a self-levelling compound then 6mm ply, followed by the tiles. Question: I'm pretty sure I need a compound that has some flexibility and one that isn't water based, but should I therefor get an acrylic one or a latex one? And, where from? Would 47264 from screwfix do the job?

I've already been advised that the best way to do this would be to remove the old floor and lay a new one. Not my cup of tea that!

[The Natural Philosopher]

Since you are plying on top I can't see it matters a hoot as long as the levelling does not break up and crumble to dust.

All you are essentially doing is filling a gap between a smooth level piece of ply and a naff old chipboard floor.

Tempted to say squirt some expanding foam on the floor and flop the plywood down on top.

Or mount the plywood using whatever spacers are needed, having pre-drilled it with holes big enough to get a foam nozzle in, and foam it after screwing it down.

Sand off any mushrooms that erupt afterwards :-)

Hmm. I have to construct a custom shower tray. I think I have discovered how to do it now...

[Lobster]

Do you really need to use the self-levelling compound before laying the ply? I'd have thought that providing you use loads of screws to hold down the ply (ie, at say 6" spacing in each direction all over the floor), then the leveller would be overkill?

David

[Graeme]

I've never used expanding foam. How hard does it set? I imagine it to be like polystyrene, but am probably totally wrong.

[Graeme]

I'm just aiming for a perfectly flat floor. Without some sort of filler/levelling compound, the ply will show the undulations that are in the existing chipboard.

[The Natural Philosopher]

No, pretty much right, in that a stiletto heel sinks right in, but you can and do lay concrete floors over the stuff - the secret is to spread the load evenly, which the ply will do. Once the tiles are n it will stiffen up even more.

If you have handled blue or pink high density foam, that's pretty much what expanding foam sets like. Especially in confined spaces where it can't bubble as much as it would like.

[The Natural Philosopher]

Yes, which is why you would normally set battens up and adjust them to the floor variation before screwing the ply down.

If the ply is thick enough I reckon the foam idea is good.

[Graeme]

It's just 6mm ply.

What about PVA mixed with sand (seriously!)? Isn't that all the latex screeds are anyway. All I need is a filler that is slightly flexible, won't crumble to dust, and is reasonably good in compression.

[adder]

Here's what you do - get a circular saw, cut around the perimeter of the bathroom floor, buy some WBP ply same thickness as the chip, cut it to size and install in the hole you created. Job done.

[Graeme]

A cunning plan! Let me think about that one.

[The Natural Philosopher]

Exactly. Up to you then. I'd still use foam or levelling compound tho - no actually in my case I'd use a load of flexible tile cement I have left over :-)

Any old flexible set gap filling cheap s**te.

>

[Michael Mcneil]

Have either of you chimps ever heard of snipping your posts?

If not, can you make a guess as to why it is a courtesy on newsgroups to do so?

[Graeme]

Ooohh! Who rattled your cage then? ;-) As someone who has posted blatant OT subjects without OT: in the subject line, and added comments to very long unsnipped posts, you're unlikely to be the best person to be calling the kettle black !

[Graeme]

I take some of that back, the bit about you making unsinpped postingings. Sorry.

[N. Thornton]

exactly. as you said initially you were advised to replace the floor. The other bodges mentioned in this thread are recipes for trouble.

Expanding foam expands with remarkable force, as I found to my consternation :) Sticking it under ply is obviously something the recommenders have not tried. At least the results would give us all a laugh :)

Tiles onto 6mm ply... come on be serious. Tiles need a _very_ rigid surface. The thicker the wood flooring you use the better. I would choose at a minimum 1". Grout between tiling edge and walls should be silicone. If you want a perfect job I'd pack the top of any joists that sag below the others.

Any kind of cement type filler used in the thinness suggested is going to disintegrate. 6mm ply offers no rigidity or support. If the chip floor's uneven the odds are its liable to move as well. That whole ideas a total mess.

Regards, NT

[Graeme]

These are only vinyl tiles, not ceramic.

Well, I've evened out most of the chip's undulations (removed the peaks), so the only places that need 'filler' are on one edge. A bit of glue and the

6mm ply with a couple of dozen screws and that should be fine.

We did get quotes to lay these tiles, and they all (3) suggested 6mm ply, filler and screws.

[The Natural Philosopher]

The theory was to leave holes where it could expand upwards, and screw the ply down firmly first. Its there to support the ply agains flexing, not to attach it. I have in fact used it so infill gaps between a flexible meter box and a 12mm plasterboard wall. It did not distort - it simply oozed out of every orifice, after which it was cut back with a plaster saw.

Easy peasy, and now that box is rigid, not flexible, and toatlly sealed agains moistire ingress.

Thats what the foam is for: To make a composite stressed skin structure. One of the most rigid possible.

That's why you use foam.

Total no sequitur.

Hmm. I suspect your knowledge of engineering structures is the real mess.

[N. Thornton]

Very different to my own experience. That foam was free to ooze out too: but it set then expanded, rather than expanded then set. And with remarkable force!

As for the rest... I assumed the OP meant tiles, not vinyl. Evidently not though. I wouldnt have any worries about putting vinyl onto a flexible floor, but real tiles dont work on even slightly bendy structures.

Regards, NT

[Graeme]

From my original posting; "I'm going to level an old chipboard bathroom floor prior to fitting vinyl tiles."

Thanks for all of your comments. This has got to be one of the best groups that I subscribe to, and it hasn't been infested with those damn trolls yet.

[The Natural Philosopher]

They do with a thick bed of flexible cement. But it all depends on what you mean by 'flexible' really...I had a lot come up on a 18mm chipboard floor that got soaked, with 4mm of cement. I re-layed some bigger ones on 10mm flexible. OK so far.