Should new plaster be primed before tiling

WLM21

Just had walls skimmed in the bathroom, ready to take tiles.

Should the walls now be primed, before the tiles are fitted

And with what ?

Thank you

llandyrnog

Hi, as a general builder we usually give the walls a coat of pva glue mixed with water the day before tiling. Hope this helps

Leif

Read the adhesive manufacturer's instructions For cement based adhesive you MUST prime the surface, e.g. with Bal Primer. Otherwise the tiles may either not adhere, or come away after a few months. For acrylic adhesives do what it says on the tub. Bal White Star says prime if the plaster is smooth, but I suspect priming is a good idea anyway.

llandyrnog wrote: »

Hi, as a general builder we usually give the walls a coat of pva glue mixed with water the day before tiling. Hope this helps

That used to be the norm, but it is not a good idea. PVA seals the plaster, preventing the tiles from binding well. Also it is water soluble, so any moisture penetrating the group and adhesive will loosen the tiles.

tlh858

Skimming walls before tiling is a waste of time any money. It also drastically reduces the weight of tiles you can use on the wall.

PVA behind tiles is a total disaster. Ideal for making a bad situation much worse. Don't use it.

As you have already got the plaster, the answer is to use an acrylic primer, and hopefully your tiles are small and lightweight, and are not going in a shower enclosure.

HarriDec

Yes, the plaster needs to be sealed as it is very porous and will suck the moisture out of the tile adhesive before it has time to 'grab' properly. Not sure what the last guy was talking about re. plastering being a waste of time and money? You obviously cannot tile a wall that has been damaged after removing old tiles, which 9 times out of 10 is the case. Besides which, how could you build a new house and tile bathrooms and kitchens without plastering them? Tile onto the block work? Don't think so. . . .

We have done hundreds of kitchen and bathroom renovations and nearly always replaster walls as they do get damaged removing the old tiles, besides which you will achieve a much better finish tiling a straight, flat wall.

You could use a coat of thinned PVA to seal the plaster, or you could 'mist coat' the plaster with a thinned coat of emulsion which will seal it and will not affect adhesion of the tiles. There are specific wall primers designed to take tile adhesive from BAL etc but if you are on a budget then mist coating will be fine.

Also, if you use a good quality grout such as Mapei and seal all tile edges with plastic trim or silicone then no moisture will get behind to affect adhesion, even in a shower enclosure.

Forgot to add, you could score the plaster to give the plaster something to grab onto.

keystone

llandyrnog wrote: »

Hope this helps

Well it won't when they all fall off. Using PVA is bonkers. You may have been lucky. Perhaps you should stick to the building bit and not the finishing bit.

Cheers

keystone

tlh858 wrote: »

Skimming walls before tiling is a waste of time any money. It also drastically reduces the weight of tiles you can use on the wall.

Well it ain't if the wall is only to be half tiled.

PVA behind tiles is a total disaster. Ideal for making a bad situation much worse. Don't use it.

Quite.

As you have already got the plaster, the answer is to use an acrylic primer, and hopefully your tiles are small and lightweight,

Skimmed plasterboard or a full plaster with skim finish can take up to 20kg/m^2. Unskimmed plasterboard can take up to 32kg/m^2. weights include adhesive and grout.

and are not going in a shower enclosure.

Why not with proper preparation? Please explain.

Cheers

keystone

HarriDec wrote: »

Besides which, how could you build a new house and tile bathrooms and kitchens without plastering them?

I think he means tile direct onto plasterboard or backerboard.

You obviously cannot tile a wall that has been damaged after removing old tiles, which 9 times out of 10 is the case.. . . .

Fill the holes and make it flat with some rapidset.

You could use a coat of thinned PVA to seal the plaster,

Oh dear....

Also, if you use a good quality grout such as Mapei and seal all tile edges with plastic trim or silicone then no moisture will get behind to affect adhesion, even in a shower enclosure.

Oh dear. With the exception of epoxy grout there is no "waterproof" grout which provides a complete barrier to the passage of water. A shower area should be tanked irrespective of the substrate.

Cheers

WLM21

Thank you for all the replies.

I removed the old tiles and the wall was in a poor state, which is the reason for the skimming.

So, a 50:50 emulsion / water mix is OK for the priming, just to prevent the fast suction of moisture. I'll be using 250 x 200 tiles. If I need proper primer. like this http://www.diy.com/nav/decor/tiles/adhesives-sealants/combined_adhesives___grouts/-specificproducttype-buildfix/Buildfix-Plaster-Primer-1kg-10137362?skuId=10558067 I'll get some, but already have plenty of paint in the house.

keystone

WLM21 wrote: »

I removed the old tiles and the wall was in a poor state, which is the reason for the skimming.

Thats understandable.

So, a 50:50 emulsion / water mix is OK for the priming, just to prevent the fast suction of moisture.

In my opinion no.

I'll be using 250 x 200 tiles.

What weight per sqm and what material are the tiles made of?

If I need proper primer. like this

I don't consider that which you linked to to be a proper primer as nothing sold by this particular shed with a Mapei label on it is a "proper" Mapei product IMO. However there is a very good chance that its a 1,000,000 x better than using PVA. What adhesive are you using?

Is there a shower involved?

Cheers

WLM21

keystone wrote: »

What weight per sqm and what material are the tiles made of?

Don't know, but they are just 250 x 200 7mm thick cheapie Homebase tiles, wot the missus picked

keystone wrote: »

I don't consider that which you linked to to be a proper primer as nothing sold by this particular shed with a Mapei label on it is a "proper" Mapei product IMO. However there is a very good chance that its a 1,000,000 x better than using PVA. What adhesive are you using?

Wickes Waterproof, the one in the blue tub

keystone wrote: »

Is there a shower involved?

Yes, at the end of the bath