How long before tiling



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#1
First of all, thanks for the advice on getting my bathroom skimmed before tiling, not just repairing with bonding - I now have a very nice skimmed bathroom.

How long should i leave it to dry before tiling? It will have had 3 weeks on Thursday. The plasterer advised not putting a fan heater in the room, but letting it dry naturally. There is no central heating.

One wall needed quite a lot of bonding.

Also, is plaster dry if it looks dry? The plasterer told me this, but I have also heard that plaster dries from the outside first.
 

johniosaif

Private Member
#2
You have left it long enough I am sure. I expect a week after plastering is plenty of time..
 

johniosaif

Private Member
#4
Should be left for 6 weeks before tiling mate, but never left it that long myself!!
News to me( not been sarcastic) We have had people tiling the next day, rush rush rush on sites these days, blame it on the one week makeover shows... I suppose it depends on how much plaster and what type of plaster and to what background you plaster on to?
 

carlos

Private Member
#5
Around a week should be fine. If it looks dry it probably is. Once it changes colour a couple more days and away you go.
 
#6
Had a training day with the Bal Tech man and that was what he told us but got to agree about speed etc and trust me I have never left it that long
 
#8
a day or 2 after it's gone pink is plenty don't forget to seal it first, i.e pva if you going onto fresh plaster
 

Jace

Private Member
#10
yep dnt use pva, there are many reasons as to not, but just take our word for it and use a proper primer
 
#11
only tiler i know who uses proper primer is the one who gets it given from firm he works for, i'm not arguing that its not the best thing to use but every other tiler i know uses pva and i never heard of any problems or had any myself. but to be safe take the other lads advice not mine
 

Fatarm

Trainee mod
#12
Pva,s a no no! This was posted by gooner on another thread hawkman started...
........PVA - Why you shouldn't use it as a tiling primer

I have to give guarantees for my work (many of these projects are commercial such as sports centre showers and changing rooms). For me to be able to give guarantees I need to follow strictly the specification of the adhesive manufacturers.

Ardex, BAL and Nicobond are the three suppliers I use most. Their products are similar in many respects, sometimes one will make products the other don't, and I also find some of there products more useful in different applications. All three of them have one thing in common, they all specify that under no circumstances may PVA be used before using any of their adhesives. If you do all guarantees are void.

OK why then? Well I asked this question to Ardex when I once had problem, I'd tiled a bathroom that had been constructed in 25mm Marine ply. Thinking he was doing the right thing, the builder got his guys to seal the ply with unibond PVA...I wasn't aware of this.

I tiled it and 6 months later every single tile fell off the ply, the adhesive solidly stuck to the tile but came clean a whistle off the ply.

We had Ardex Technical down to the site to compile a report, the basis of which was it's the PVA that causes the problem.

When you treat a surface with PVA it partly soaks in and partly sits on the surface of the substrate much in the same way as wallpaper paste.

If PVA gets wet it becomes slightly live again, it doesn't completely return to it's liquid state but it becomes sticky.

When you spread tile adhesive onto the wall, the water in the adhesive makes the PVA live and stops the adhesive from penetrating the substrate and providing a mechanical grip. Basically your tiles, grout and adhesive are being held to the wall by a thin layer of PVA.

Most tile adhesive works by crystallising when it sets (some are slightly different such as epoxy based ones) but generally they all work the same way. Once the adhesive starts to set crystals from and expand into any imperfections in the substrate surface (at a microscopic level) to create a grip. PVA stops this process by creating a barrier between the substrate and the tile adhesive.

Ok so what's the difference between this and Ardex or BAL primer, well basically the tile manufacturers primers soak right in to the substrate and stop the sponge like "draw "effect but they don't coat the surface in any way, they are an impregnator as opposed to a barrier. They also stop a chemical reaction occurring between the cement based adhesive and a plaster substrate, a known problem know as "Ettringite failure"

I hope this clears up any misunderstandings.
So only use PVA before tiling if the adhesive manufacturer specifies it in the instructions.
 

gooner59

Private Member
#13
Great advice from mr Fatarm Here !! even when i plaster i have substituted pva for SBR a better product than pva
 

Nisus

Elite Member
#15
I met a Plumber on a job once & he pva's plaster the next day then tiles & grouts it that day ffs!!!! :RpS_scared:
He once laid a porcelain show tray onto floorboards with dri wall adhesive lmao :RpS_laugh:
How do these people keep getting work ffs!! He's always busy :huh:
 

johniosaif

Private Member
#16
I met a Plumber on a job once & he pva's plaster the next day then tiles & grouts it that day ffs!!!! :RpS_scared:
He once laid a porcelain show tray onto floorboards with dri wall adhesive lmao :RpS_laugh:
How do these people keep getting work ffs!! He's always busy :huh:
cost conscious people hire him, never cheap to do it correctly is it, always cheaper to bodge
 
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#17
educated me that fatarm i will bare that in mind next time i tile anything, could be quite expensive to rectify if a room full of tiles drops on the floor. like i say i only ever used weakish pva as do tilers i know and no probs so far, but if it goes tits up and you not followed the specified method the finger points at you
 
#19
OK many thanks, will give the tiler the go-ahead to start on Monday.

Will use BAL tanking kit for the bath area and a proper tile primer (not PVA!).
 

lucius

Well-Known Member
#21
Luckily you have been given some good advice and some crap advice but ime sure you haveworked out which is which, in future if you want some advice on tiling go On the tilers forum, i hope you are not putting any thing to heavy on your skimmed walls.
 
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