tiling over new plaster

[Micilin]

Richard C -

Cheers for the info -

So -

No problem using bonding if properly keyed, but bonding must be skimmed.

We know that skimming s&c render reduces the weight of tiles that can be used but-

Do you know what exactly the properties of finish are that make it different to bonding , in this context ie reaction to tile adhesive. Or is it just BG wanting to sell more finish?



While I'm at it does anyone know why bonding it now Thistle instead of Carlite ?

 

[roughcaster]

I've no idea why the change of name from Carlite to Thistle,, maybe it's a British Gypsum thing, and they would know the answer. Do you remember Carlite Metal Bonding plaster? It was used for eml etc. Nowadays, one bonding plaster product seems to do everything. It was hard work back then as well, because each bag of plaster, and cement, weighed in at 50 kilos, = 1 hundredweight in old money,,,, kept you fit though.

 

[Richard C]

We know that skimming s&c render reduces the weight of tiles that can be used but-

Do you know what exactly the properties of finish are that make it different to bonding , in this context ie reaction to tile adhesive. Or is it just BG wanting to sell more finish?

I do know a manufacturer of cement boards & plaster products that says you must only use their “special” plaster but when pushed, didn’t go so far as to condemn what I was proposing to do using BG Multi; I still do it & have had no problems to date . I can be a bit of a cynical git but I wouldn’t go as far as that in this case; it’s not just BG but the Tile Association & the majority of adhesive manufacturers all saying the same thing. I’ve got away with it in the past & I’m sure there are countless others who have but going against such strong recommendations seems a bit pointless. You would only need one failure & it would cost a fortune to put right; you would have absolutely no claim under their warranty, these can be difficult enough to claim on anyway & if you ignore their recommendations & guidance, you can guess what their reaction is going to be.

Bonding it has a fair bit of Vermiculite in it which makes it quiet course grained, soft & highly absorbent; it’s not just Bonding, BG place the same restriction on all their base coat plasters except Dri-Coat but I’ve never used or tilled over it. Multi as you know has a much finer texture, is very hard & provides a much stronger finish.

While I'm at it does anyone know why bonding it now Thistle instead of Carlite ?

Don't know for sure but marketing probably; we now have “new Bonding” which we all know is much smoother & easier to use

Edit
All gypsum based plaster/plasterboard products must be primed before using powder based adhesive, it’s to avoid a chemical reaction between the cement I the adhesive & gypsum in the plaster; this also applies to floor tiling where the anhydrite (gypsum) based screeds are used.

 

[Micilin]

I've no idea why the change of name from Carlite to Thistle,, maybe it's a British Gypsum thing, and they would know the answer. Do you remember Carlite Metal Bonding plaster? It was used for eml etc. Nowadays, one bonding plaster product seems to do everything. It was hard work back then as well, because each bag of plaster, and cement, weighed in at 50 kilos, = 1 hundredweight in old money,,,, kept you fit though.

I remember 'Metal Lathing' plaster - mid 80s.

Don't let's get started on the bag size - no forklift, 20 ton deliveries handballed off, mixing with a larry, shove or rake ...............

 

[Micilin]

Richard C,

I agree no point chancing it-( and to skim it you only need it flat so not as time consuming as finished work) . Imagine going back into a finished bathroom to sort it out...............


I still don't see why if the finish plaster has to be sealed, why this sealer won't seal the bonding.

Perhaps because it is easy to seal the entire flat surface of finish, as opposed to the pits and holes that may be in bonding.