Sealing Moisture resistant plasterboard - Tile Advice

[graham35]

Sealing Moisture resistant plasterboard
Hi I am new here, I have been reading through many of the threads here and see that there a lots of knowledgeable people here and hopefully I can get some answers to a problem I find myself in.

I am a retired builder and recently have refurbished a bungalow for my wife and I, part of this work includes and en-suite bathroom, a shower room and the kitchen which have all been tiled. We removed all the old wall tiles from the existing bathroom, which left the walls in a rough and poor condition, the tiler said "that's no problem, I have tiled over much worse than that" However I decided that to make things easier for him and to ensure we get a good job done, we boarded out the areas with moisture resistant plasterboard bonded dab and dot to the existing walls, we also carried out some additional plastering and essentially gave him all new surfaces to tile.
He said he would prime the new plaster and fill and seal the joints, corners, screws and also where the moisture resistant boards meet the bath and shower tray, saying that it will make it water tight, if ever any moisture were ever to penetrate the tiles or sealant.

Sorry my question, what would you have used to fill and seal the moisture resistant plaster boarding?

Sorry for the long story, but from now I will try and keep things much shorter as there is much more to come ....

Thanks in advance
Graham

 

[graham35]

64 views and no answers, so is no one using moisture resistant plasterboard or filling the joints and corners etc, I was made to believe this was done thing.

I would appreciate your help please guys.

Thanks

 

[JasonJfix]

I’m a novice but I’ve done research. Firstly according to manufacturer you’re not supposed to dot and dab green moisture board because of the high silica content.
My understanding from Mapei is that green moisture board doesn’t need priming before tiling or applying a tanking membrane.
If I was tiling on moisture board directly, and it was a wet area, I would tank it first with a tanking kit (eg Mapei) then tile on top.

 

[Cherie]

Things You'll Need

Greenboard has a waxy surface that makes it difficult to get tiles to adhere to it. One solution is to coat it first in a layer of Kilz or other flat sealing primer, which will stick to the board while providing a suitable surface to hold the tile.

www.hunker.com › how-to-tile-ove...

How to Tile Over Greenboard |​

I was told something similar to this on a bathroom tile

 

[Winkers]

Sealing Moisture resistant plasterboard
Hi I am new here, I have been reading through many of the threads here and see that there a lots of knowledgeable people here and hopefully I can get some answers to a problem I find myself in.

I am a retired builder and recently have refurbished a bungalow for my wife and I, part of this work includes and en-suite bathroom, a shower room and the kitchen which have all been tiled. We removed all the old wall tiles from the existing bathroom, which left the walls in a rough and poor condition, the tiler said "that's no problem, I have tiled over much worse than that" However I decided that to make things easier for him and to ensure we get a good job done, we boarded out the areas with moisture resistant plasterboard bonded dab and dot to the existing walls, we also carried out some additional plastering and essentially gave him all new surfaces to tile.
He said he would prime the new plaster and fill and seal the joints, corners, screws and also where the moisture resistant boards meet the bath and shower tray, saying that it will make it water tight, if ever any moisture were ever to penetrate the tiles or sealant.

Sorry my question, what would you have used to fill and seal the moisture resistant plaster boarding?

Sorry for the long story, but from now I will try and keep things much shorter as there is much more to come ....

Thanks in advance
Graham

Hi Graham, you've raised an issue that I have posted a question about ie. 'tanking'.
It seems that I'm the only amateur tiler who doesn't understand why we need to tank a shower wall before tiling!
The experts tell me that water can penetrate grout and adhesive. That I understand, but, if water penetration occurs the tanking will protect the wall but not the porous adhesive and grout.
Logic tells me that wet adhesive and grout will not support tiles. What then?

 

[Dave]

Hi Graham, you've raised an issue that I have posted a question about ie. 'tanking'.
It seems that I'm the only amateur tiler who doesn't understand why we need to tank a shower wall before tiling!
The experts tell me that water can penetrate grout and adhesive. That I understand, but, if water penetration occurs the tanking will protect the wall but not the porous adhesive and grout.
Logic tells me that wet adhesive and grout will not support tiles. What then?

Cement based adhesives and grouts can be fully submersed in water, so a soaking from a showers won’t effect it’s stability.

 

[graham35]

Thank you for the replies, my tiler eventually told me that he had sealed the green plasterboard to the shower trays and bath with Bal sealant (normal sealant ) and also the joints in the plasterboard and corners, but not the screw heads, and then stuck the tiles on, buttering the tile adhesive to the tile and then fixing it in place. I know that he did not seal one of the shower trays to green plasterboard, as I had to replace the sealant on the face to the tiles as after 3 months use of 2 showers a day the sealant had let go of the shower tray and some of the corners, he said that it is normal to have to re-seal every 3 to 6 months (my last house had the original sealant from about 10 years) his sealant let go because he did not clean off the grout dust from the tiles and shower trays). After I cleaned off his sealant, I was able to push a nail file between the shower tray and tiles all the way through to the studwork base plate without any resistance.
I cannot believe that using normal sealant on the green plasterboard is the right thing to use.