Can you use sika laytex on interior walls. Before tiling

Hi Beverley SBR Sika Latex is used as an additive for improving cementitious mixes for concretes and renders. If you can specify the location of internal wall/s (i.e. bathroom/shower room/basement etc.) I maybe able to advise you further.

Yes Sbr can be watered down 50/50 and used as a primer coat.

No it should not be used as anything other than the manufacturers specs,it is an ad mix.I would use a priming agent specific to your requirements.

I would always use a tilers primer rather than an addative from a mix. They tend to be thick and create a skin rather than getting into the surface. My preferred primer is the palace primer, is soaks in and makes the surface feel almost tacky instead of just creating a skin