Wall Sealant Prior to tiling?

[Quarkrad]

I have done a lot of work (too much wife says) preparing to tile bathroom. I have built stud wall for corner shower unit (one wall **** panel one brick/plaster) and ordered Dunlop tanking kit to seal. My walls are a mixture of existing tiles (cleaned, taken out loose tiles and filed with new plaster), 2.5 sq m of new plaster and existing plaster walls with old wallpaper stipped off. Appreciate it would have been ideal to take off old tiles but for reasons I will not go into they need to stay on. The walls are clean and ready to go (tile) but I have doubts. I am happy about the shower area as I will put on primer and the waterproof layer from the tanking kit but what about the rest of the walls? Advice seems to be keep the existing tiles clean to tile over but various opinions about the other wall. For the new plaster should I put up some bonding/sealing poduct before I tile? And do I leave the existing, wall paper stripped, walls alone? Some say bond/seal with 2:1 PVA but I can see the arguement others say about breathing and never touch PVA. Any advice on final wall preparation much appreciate.

 

[grumpygrouter]

If in doubt, prime the walls is a general rule. You didn't say what adhesive you are going to use but one thing that is ABSOLUTELY DEFINATE - DO NOT USE PVA.

Use a "proper" acrylic based tiling primer sucha s BAL Prime APD or Ardex P51.

PVA is not suitable for tiling for various reasons and this has been debated many times here in the forum. Do a "search" in the box at the top for "PVA" and see what comes up.

You new plaster area should definately be primed. The tiles area should be cleaned with sugar soap and dried off. As you are tiling onto tiles it is wise to be using a flexible adhesive such as BAL white star. This would be adequate for all the walls but the area you are tanking would be best to use a powder adhesive not tubbed. Alternatively use a flexible powder adhesive everywhere or a standard adhesive with a flexible admix.

 

[dock]

For your information our advice would be to prime only the plaster areas with Primer G.........................and as grumpygrouter points out definitely not PVA..................clean the existing tilies as described then fix over the whole area with Keraflex Maxi, a genuine S1 single part flexible adhesive

dock

 

[Quarkrad]

Tiling shop use BAL White tub that has additive - they suggest as adhesive has adative I do not need to prime/seal. Is this fair advice? Having gone to all this trouble cost is not an issue (small bathroom). Is priming an over kill now adhesive has additive? Thanks.

 

[grumpygrouter]

Using tubbed adhesive means that the adhesive dries by way of evaporation. As such, there needs to be some way for the moisture to "disperse". If you are tiling over glazed tiles or the "waterproof" tanked area, this evaporation takes much longer therefore the drying process is longer (days!). Powder adhesive on the other hand sets by way of a chemical process that does not rely on evaporation. That is the reason why I recommended powder adhesive for the tiled area. If you use powder adhesive you can grout much earlier as it will not effect the setting process like the tubbed stuff would be effected.

Powder adhesive would require priming of the plastered area as a neccessity. Primer is not expensive and is quick to do so you would be as well to consider it for all the areas that would require it.

You also need to bear in mind that British Standsrds (and therefore BAL) recommend that a shower area be left for 2 weeks after grouting before being brought into use.use

Your supplier was correct in that White Star is effectively self priming,

 

[Quarkrad]

Thank you for your reply - makes perfect sense. I will buy some primer and powder adhesive. I only have expereince (good) of Mapei powder adhesive that I used to tile kitchin floor. Can you tell me equiv BAL powder to go with BAL primer or Mapei primer I could buy? Your advice much appreciated.