Tiling on existing tiles issue

[musky72]

Hi there,

We have recently renovated a bathroom and we removed the majority of existing wall tiles, some were very hard to remove so we left them in place and applied a thin coat of plaster to make the wall even.

After we applied the new tiles over the top, the tiles that are on plaster are fine but the ones that are sat on top of existing tiles have large patchy marks on them.

I have been told that it is because the adhesive is not drawing into the plasterboard and therefore is taking a lot longer to dry, I am doubtful as it has been 3-4 days now and they don't seem to be getting any better.

Does anyone else have an experience of this? If so, how did you remedy it?

Thanks

 

[tpt]

how big and what type of material are they?

what adhesive did you use?

 

[Graemevw]

It does sound like trapped damp.

Have you grouted yet? If not, dont utill the staining goes away.

If you used a dark adhesive (grey) and the tiles are white, the staining may be permenant, but my guess is it will dry out.

 

[musky72]

Not grouted yet, used a waterproof adhesive as it is a bathroom, the adhesive is light grey (white).

I have a heater in there now, will see if the patches dry out.

We did take one off the wall a couple of days back and that did clear up after 24 hours so I am hoping it is simply a little damp that has become trapped and should dry up once the heater has been on for a while.

Thanks

 

[tpt]

assuming its a ceramic or porcelain and not natural stone it may be ok given some time. how big are the tiles?

 

[musky72]

Tiles are approx 300mm x 250mm, they were applied over some old 60's tiles.

Hopefully given some more time the marks will fade.....(fingers crossed!!)

Steve

 

[flameport]

Not grouted yet, used a waterproof adhesive as it is a bathroom, the adhesive is light grey (white).

Powder or ready mixed?

If the latter, it will take weeks/months/never to dry out, as stuck between two tiles means there is nowhere for the moisture to go.

 

[tpt]

as the poster above says, on that size tile, on top of tiles a ready mixed adhesive will take a very long time to set, because of this the moisture is trying to escape through the tile

 

[musky72]

It was a ready mix adhesive for use in bathrooms.

 

[Richard C]

Plastering over the tiles was a big mistake; plaster is not an ideal tile surface anyway but will have a very weak bond over tiles, did you use any sort of bonding agent or primer? With that size tile, you may also be getting near the weight limit for plaster as well - 20 kg/sqm (including addy & grout) when sound & in good condition. Tile over tile is also a bad idea & poor practice but you can get away with it if no other options (extremely rare) but you have to use quality trade adhesive & if attempting it with tiles that size, you should use powder cement adhesive. Tub mix will take forever to dry/set & sometimes it never does before the tiles fall off & that’s if the plaster bond to the tile doesn’t fail first due to excessive moisture. Tub mix relies on evaporation & sandwich a water based adhesive between two glazed tiles & the water has nowhere to go except through the grout lines.

If someone is advising you, you’ve been given very poor advice!

 

[joe-90]

I think I'd pull the lot off and start again. You should hopefully be able to clean the tiles up.

 

[musky72]

I agree, pulling them off and restarting, trouble is, its only the ones where they have been tiled onto existing tiles that seem to be affected, all the others are A1 !!

I think the underlying issue is that the older (60's) tiles were bonded to a very thin plasterboard and if you try to remove them from that, the board simply crumbles away underneath them.

I'll give it a little longer though doubt that the patches will clear up anytime soon, lets hope a bit more heat will sort them out !

Thanks all.

 

[Richard C]

I think the underlying issue is that the older (60's) tiles were bonded to a very thin plasterboard and if you try to remove them from that, the board simply crumbles away underneath them.

If the original tiling over plasterboard was done correctly using good quality tiling materials, it should be expected that the plasterboard will be destroyed in the tile removal process but this is only something you may learn/know from experience. An experienced tiler would expect to rip the lot down & start again by replacing the PB as a matter of course. It’s usually less hassle, quicker & gives the opportunity to replace the PB with a waterproof tile backer board in wet areas which is a far more suitable tile base.

I'll give it a little longer though doubt that the patches will clear up anytime soon, lets hope a bit more heat will sort them out !

If the patches are caused through trapped moisture from the addy, it may eventually clear but there is a risk moisture (or rather the bacteria growing in it) will stain the tile underneath the glaze. A little ambient heat will help but I wouldn’t attempt to force it by using excessive heat or it may cause even more problems. I would be more concerned about the adhesive bond over the existing tiles & the effect that prolonged moisture exposure will have on the bond of the plaster over the tiles (which is effectively holding the tiles up). Even if it eventually dries out, you may be doomed to early tile failure due to poor tile bonding.