priming/sealing plasterboard

[tommyl18]

whats the best primer and sealer for moisture resistant boards before plastering?

 

[PrenticeBoyofDerry]

British Gypsum recommend using thistle bond.
http://www.british-gypsum.com/produ...le_plaster_bonding_agents/thistlebond-it.aspx

 

[Richard C]

whats the best primer and sealer for moisture resistant boards before plastering?

Thistle Bond-it as PBD; but I assume your just finishing outside the tile zone & not intending to tile over afterwards?

 

[tommyl18]

im going to plaster it then tile it after

if thats the case then i could just mix pva and aggregate together and brush that on because thats all thistle bond it is with paint in so you can see where youve painted it

 

[Richard C]

im going to plaster it then tile it after

No, No, No, No No don’t do that; if you’re tiling then there is no point in skimming you are just making work for yourself, just tile straight over the PB. You only need to prime with Bond-it if you’re plastering, not if tiling; but if your tiling with cement addy you do need an acrylic primer over gypsum plaster & boards.

if thats the case then i could just mix pva and aggregate together and brush that on because thats all thistle bond it is with paint in so you can see where youve painted it

Bond-it may well have PVA in it I’ve no idea but I doubt it’s just PVA mixed with paint , where on earth did you get that little gem from ? You are also mistaken to think you need primer to tile over MR PB; if you need to prime (e.g. using a powder cement based addy), you should use an acrylic based primer which is not water soluble. Standard PVA (poly vinyl acetate) is generally of no use when tiling as it always remains water soluble, it should never be used on a tile base, particularly in wet areas.

 

[tommyl18]

im skimming it all because its only partially being tiled and the customer is not sure where she wants the tiles yet and its a small bathroom easier just to skim it plus it just looks neater than patchs everywhere

I was talking to a chap at the tech department at ccf and he said thistle bond it is just pva mixed with sand and they add a colour to it so its just easier to see where youve applied it they reccommended i just make my own and thats what ive been doing for years just mix pva with sand or bonding and apply it to the wall 24 hours before and then plaster will stick like **** to a blanket i do it a lot on smooth back grounds or back grounds like waterproof paint or backgrounds im not to sure on

 

[Richard C]

I was talking to a chap at the tech department at ccf and he said thistle bond it is just pva mixed with sand and they add a colour to it so its just easier to see where youve applied it they reccommended i just make my own and thats what ive been doing for years

If that’s entirely true I’d be surprised but we all know it’s over priced.

just mix pva with sand or bonding and apply it to the wall 24 hours before and then plaster will stick like s**t to a blanket i do it a lot on smooth back grounds or back grounds like waterproof paint or backgrounds im not to sure on

I don't disagree with you about a PVA/sand/Bonding mix for adhesion when skimming over difficult surfaces glazed tiles or even MRPB but I would not recommend you try any sort of PVA concoction as a primer for tiling, even less so where cement addy is being used on large format tiles as plastering will reduce the maximum tile weight you can lay & could be a problem if she is having large format tiles; that was my main concern.

It may seem a little strange but whereas PVA is often the plasterers best friend, it can be a tilers worst enemy!

 

[tommyl18]

yea pva can be funny stuff, I confirmed it with ccf today and its pva with silica sand ie kiln dried sand they also stated that if your going to make your own pva/sand mix always use kiln dried sand and not building sand/ sharp sand etc, i can underdstand there point if you are doing it in areas with damp because of the silica content but not sure the reasons for any other circumstance as ive always used building sand previously with pva and never had any problems

I agree with you about tiling onto PVA Richard C

 

[Richard C]

I confirmed it with ccf today and its pva with silica sand ie kiln dried sand they also stated that if your going to make your own pva/sand mix always use kiln dried sand and not building sand/ sharp sand etc, i can underdstand there point if you are doing it in areas with damp because of the silica content but not sure the reasons for any other circumstance as ive always used building sand previously with pva and never had any problems

Interesting & surprising; even more so that they were open & prepared to give the game away

 

[tommyl18]

they are really good at my local merchants and they know its just a rip off for what it is