slight worry

[1john]

I have just tiled around my bath (which will have a shower over) one wall was bare plasterboard and the other was plasterboard with skim finish.

I primed the walls with a product from a local tile shop, dunno what it was called except for 'primer' it was blue if that helps and then I have fixed the tiles using BAL CTF3

My concern is that now that i have fixed all the tiles I decided to read the back of the bag, which says i should have applied two coats of SBR.

Has anyone made this error before and do you think that it will be ok?

 

[1john]

also.... is the dunlop white grout with microban in it a good product?

Thanks in advance

 

[Richard C]

Who advised using CTF3? You really should have used a flexible addy over the PB or mixed the CTF3 with Admix AD1 to give a degree of flexibility. The cement in powder adhesive reacts with Gypsum & Gypsum plaster which affects bonding; Gypsum surfaces should be primed with SBR primer (BAL Prime or Prime APD) to prevent the likelihood of any reaction & to improve tile adhesion. Can I ask what type of plasterboard it was? What size/weight are your tiles?

Microban is an antibacterial/antifungal agent commonly used it grout products. Dunlop & BAL are now the same company; BAL are high quality products (which I use) & I suspect they have consolidated many of their product range but am not entirely certain; Dunlop are slightly cheaper. Which particular grout did your use; assume it was a flexible grout?

 

[1john]

Thanks Richard, I was hoping you would reply, your input on the plastering forum has been second to none on my topics and countless others

All plasterboard is standard (not MR) 12.5mm; on the length of the bath it is foam bonded to the substrate which is some type of block construction.

at the head of the bath I have double boarded with silicone between the boards onto 4x2 at 450mm centers (900mm wide stud partition) screwed at 100mm intervals with 3/4 ply fillet behind which is cut between the studs.

I chose ctf3 as it seemed the best product it seemed the best product i could afford. With strong pressure to the boards there is no flex.

So dunlop and BAL are the same company, I just wanted the best grout i could afford, we are on a very tight budget but I am trying to use the best materials I can afford.

I haven't grouted yet but purchased the dunlop grout a few days ago. I chose it because of the microban, i have used sealants with microban and am aware that it is a good product, just questioning the dunlop brand but feel confident with it now.

 

[Richard C]

Board construction or lining (even cement board) will always be subject to a degree of flexing & movement just through normal expansion & contraction, especially stud work. For this reason you should always use a flexible tile adhesive & grout over boards. CTF3 isn’t flexible & although you can improve it with Admix AD1 but it won’t be as good as a proper flex addy; depending on your tiles size/weight you should have used either this;
http://www.bal-adhesives.co.uk/products/white-star
or this;
http://www.bal-adhesives.co.uk/products/rapidset-flexible
+ primed the PB/plaster skim with this;
http://www.bal-adhesives.co.uk/products/prime-apd
to prevent any reacting between the cement & Gypsum.

Cement powder addy is usually only necessary when tiles size/weight gets near or exceeds 300 x 300mm, was this a reason for choosing it? The primer is also important to avoid any reaction when tiling over Gypsum plaster or boards. The other thing you should be aware of is their is weight limit 32 kg/sqm for unplastered boards but this drops to just 20 kg/sqm when skimmed & this doesn’t include the weight of 2-4 kg/sqm for the addy & grout, depending on what type of addy is used. The grout should be OK, had a quick look & it appears to be flexible.

My biggest concerns would be that;
• you’ve not used a flexible addy
• not tanked the PB before tiling
• did not prim the PB/plaster skim to prevent a reaction between the cement & the Gypsum.

Now that’s it’s all done there is little you can do now except finish it off & see what happens. To a large extent it’s going to depend how heavily used it is & how much water you splash about. Many new builds are done to the absolute minimum spec. but this is probably more through builder cost cutting than a lack of understanding of suitability of the materials; the problem is that they tend to have a relatively short lifespan, in many casses less than 5 years before it all has to come down & be redone; you wouldn’t believe the state of some of the plasterboard behind the tiles that I rip out during refurbishments, sometimes on quiet relatively new properties.

 

[1john]

Well some good and bad news, i did prime the bare plaster and the skim, my tiles are 250x400 ceramic, i havent weighed a box of them, which covers 1.6m2 but the dont seem to be as heavy as a sack of dog food

Tha grout is flexible, i forgot to answer you, sorry.

I suppose as you have said, i am going to have to suck it and see. i did silicone the corner between the plasterboard stud and the foam dabbed wall and have left a 2mm gap down the corner to jam with silicone for a flexible seal on the corner.

Thanks for your help, and you can feel assured that this is a mistake that I wont make again. There are too many BAL adhesives IMO, i got quite confused at the time but was trying to compile an order on line with tiles and trim, it was quite late and I wanted to get the order in, in hindsight i should have waited and asked

 

[Richard C]

You picked the right type of adhesive for the tiles you’re using, but unfortunately the wrong one. As long as you used an SBR based sealer which is waterproof & not standard PVA which isn’t, you should be OK. Running a bead of silicone down the corner instead of grouting is good practice.

There are too many BAL adhesives IMO

I’m inclined to agree with you on that one; some of their products seem to have almost identical spec. sheets making it difficult to decide which is the most suitable even when using BAL’s product selector. Rationalisation would be a good idea IMO, I tend to stick with just the few I have experience with & know work for me.

 

[1john]

Well it wasn't SBR and it wasn't PVA, it was a blue primer, it did look to have left a shine on the surface, it wasn't cheap either, I got the price down to 12.75 for a litre, they wanted 18 squid odd initially

perhaps i will coat an offcut of board and see what happens when i go over it with a wet sponge later on.

Thanks for your help Richard, very much appreciated