General consensus is to use Water grade ply/marine ply or whatever its called to screw to floorboards in a bathroom prior to floor tiling My question is why? Surely, if the water gets past the tiles your buggered anyway ? so why the need? (expecting to be flamed for this but hey ho)
Actually, WBP ply is plenty good enough. Marine ply is many times the price for almost no additional benefit in this application.
Actually, a little water weeping past probably won't hurt WBP ply, especially if it gets a chance to dry off. Chipboard will be like soggy cardboard in no time.
Christian.
I guess that you'll be ubggred rather sooner if you use ply that isn't water resistant, or chipboard that isn't moisture resistant. That's probably all, although I'm prepared to be gently enlightened.
In theory you are correct but in practice it's virtually impossible to stop all water/moisture getting behind the tiles.
If you used non waterproof ply it'd swell up, and possibly rot, causing further problems.
sponix
ah fair nuff ta
Pardon the obvious but what does WBP stand for when referring to ply?
WBP is a TLA. In fact TLA is just another TLA.
Chris.
Weather and Boil Proof
I believe it is "Wash and Boil Proof". I am willing to be disabused of this...
Christian.
Look at it this way... suppose in a couple of years you detect a slight damp patch on the ceiling below. Subsequent investigations show there's been a very slight leak through the bathroom floor. With WBP ply, you can just fix the leak and job done; with chipboard for example, the flooring would have turned to mush (think weetabix) and would need replacing (that's if the loo hasn't already landed in the hall...!)
David
Probably about as good to eat as well.
Steve S
Well, I won't be tempted to boil any plywood then.
The point about 'boil proof' is that water can be trapped in cavities in sodden 'standard' plywood and, if subsequently exposed to hot sunshine, may boil and result in suface damage such as bubbles. The difference between WBP and marine-grade is that the latter is manufactured without significant air cavities which could trap water.
Otherwise both types are otherwise similar, at least that's SFAIUI
hope that clarifies the issue.
Have you ever seen water boil when exposed to sunshine?
'WBP' ply has water resistant glues, which means it won't delaminate if it gets wet.
Proper moisture resistant MDF (p5/V313) is also pretty water resistant, (but this doesn't include any old cheap green coloured crap from a BM) See:
Both will rot if they remain wet for a long time though. The water resistance of either can be tested by boiling an offcut.
There is a 'WBP fan club' on here that believe all MDF will behave like 'weetabix' if it gets wet, but a google through the archives will show others have found this not to be quite the case :)
Personally I don't like using WBP if there are other alternatives, as a lot (all?) of it comes from tropical forest in Asia or South America.
I'd seal the top and edges of the wood with a high quality exterior woodstain like Sikkens or some other sealer, making the wood waterproof. Then any small leaks under the tiles could dry out though the wood as water vapour without the wood getting soaked.
cheers, Pete.
Personally, I haven't paid this year's subs yet; but I think the 'weetabix' reference is usually reserved for chipboard rather than MDF... it's chipboard which is affected spectacularly, not MDF.
David
Actually, its not.
I have plain old green chip. Yes, I had a leak from the toilet . Yes, the chip swelled up and buggered my tiles.
Yes, that was how I =actually noticed I had a leak.
The tiles were crap anyway, so I removed the bog, let the chip dry out (it returned to more or less normal size) re tiled the floor with nicer tiles, and sorted the leak out.
Its fine. The secret is to have a warm dry room so that when you miss, or splash or whatever, the water dries faster than it penetrates the grout.
Only if you didn't fix the leak.
Its the same with showers made of aquapanel. Unncessary., Ordinary plasterboard is fine IF your tiliing is good, and you seal evenyhwere.And water doesn't collect on a groutline.
I had one leak in one shower - down to water seeping behind a place where the shower hose emerged - and got plaster swelling and water marks in the adjacent corridoor.
I fixed the leak, and the swellling subsided, and a lick of paint was all it needed.
You can be TOO precious about these things. If water gets behind your tiles you are in deep doggies anyway.its a slightly different thing with say a vinyl floor, where the edges will leak anyway.
TNP
I feel a breath of fresh air. It's nice to see some pragmatism for a change.
MBQ
OTOH why not make the surface under the tiles and cement both waterproof and watertight, then any leaks though the grout won't matter so much.
Just use a good sealer on the boards, then use sealant and tape on the joins and outside edges. And make sure all fittings that screw into the boards have a clearance hole that is filled with sealant too.
Using waterproofer on the grout or non absorbent grout would also help slow water penetration.
cheers, Pete.
It certainly will do so if a small bubble of water is trapped inside a void and heated by a direct exposure to the sun on a hot day. What's more the steam pressure generated will be considerable.
x score and ten years ago I used a lot of marine grade on a project where good performance in damp conditions by the ply was needed. There wasn't much price difference in those days so I just bought 'the best'. 3 or 4 years later in the late 90s wanting more marine grade I found it had escalated sharply in price versus WBP. That forced me to check on the difference between the 2 types.
My information from official trade sources was just as stated in my previous post. 'Boil' refers the ply being resistant to the effect of trapped water boiling inside the ply eg by exposure to hot sunshine (or other heating). Be delighted to hear contrary info, no doubt you'll post with chapter and verse.
Now I just use WBP unless the ply could be exposed to sunshine.
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