Mapei primer G required?

[Stan7]

Please can anyone advise if Mapei primer G is required when using Mapei buildfix wall tile adhesive on newly (8 weeks ago) skimmed bathroom walls? Or can I just use the adhesive straight onto the plastered walls?

Thanks very much for any advice

 

[Rich Midge]

Is this a ready mix? Should clearly state on the bucket if a primer is needed. Some tubbed adhesives are self priming. Have the walls been skimmed to a polish? If so I'd be giving them a rub over, dust off and prime.

 

[Stan7]

Yes, it is ready mixed and no mention of primer being needed on the tub. No, the walls are not skimmed to a Polish.

 

[Rich Midge]

Does it say self priming? Sorry I'm not familiar with mapei products. Generally speaking no harm will ever come from priming as long as it's absorbed by the plaster, it's there to aid adhesion.

 

[Stan7]

Sadly my mother in law bought the adhesive so I won't be able to check until tomorrow. She did tell me it doesn't mention using a primer but I thought using the primer could only help.

Thanks for your help, Rich

 

[White Room]

With tub gear it need absorption from either the tiles or the wall surface.

 

[Stan7]

whitebeam, so the primer is worth using as it will provide absorption for the adhesive?

 

[White Room]

whitebeam, so the primer is worth using as it will provide absorption for the adhesive?

The primer makes a barrier between surfaces, cement based adhesive to plaster for example and also reduces suction, tub adhesive is water based and air drying and needs absorption to dry.

 

[Stan7]

Had a look at some info regarding the primer and it is a "water-based synthetic resin primer for treating gypsum substrates prior to installing tiles with cementitious adhesives".

As the adhesive does not appear to be cementitious and I don't think the substrate can be classed as absorbent I don't think I will use the primer.

 

[Rich Midge]

New plaster unless finished to a polish is very absorbent. Granfix Multifix along with the Ultra ready-mix tubs are self priming, most other tubs in my experience aren't. Personally I'd prime. I use sbr 4:1 on new plaster. I've seen acrylic tubbed addy just peal away from unprimed plaster.

 

[Stan7]

Good to know, Rich. Is there any disadvantage to using a primer?

 

[Rich Midge]

Only if you over apply. In the short term you may find it takes a little longer to dry but when it does dry the bond will be stronger. I'm presuming you're fixing ceramics? What size are the tiles?

 

[Stan7]

Good to know. Yes, ceramic tiles that I think are 200mm x 200mm

 

[Rich Midge]

Then you should be all good to go. Leave it as long as you can before grouting and don't exceed the bed thickness. As @whitebeam said tubbed adhesives require air to dry so it's imperative you leave it as long as you can. Best of luck with it.

 

[Stan7]

Appreciate your help, Rich. It's been a good 15 years since I last did any tiling but wanted to help out my mother in law as she has been through a tough time lately.