Plastering - reducing suction

[Porker]

I'm after some plastering advice. I have a job to help out my sister who needs a fair bit of work done on her old house. I have no problem skimming board and floating and skimming the brick walls but one wall is stone which is some sort of local slate / shale with lime mortar at a guess. (One bonus is that it is very flat.) I want to use a sand / cement backing but reckon it will suck the water out like a sponge.

Should I soak the wall using just water or spray with a 4:1 PVA coat. Any tips appreciated?

 

[legs-akimbo]

give it a good scratch coat first with plenty of waterproofer in, this will reduce the suction on the floating coat. Float a coule of days later.

 

[Porker]

Thanks. Sounds like a good idea. I have never used waterproofer before. Can I also use plasticiser which I normally use (Admix) in the same batch?

 

[legs-akimbo]

waterproofer will do the same job as the plas anyway and you can buy a product called medusa too which you add to your gauge, supposed to be very good for your type of problem... never used it myself as we cant get it here.