I'm a bit confused here?

[George]

Stone work(Sandstone block) is getting painted with a base emulsion coat,builder says any bad areas will be filled in when the paint has dried with sand&cement mixed with an expoxy.

Will it adhere soundly to a painted emulsion surface?

As far as I know a sandstone cannot be successfully repaird ie I was told by a mason some years ago that to get a successful flat repair job on sandstone it has to be randomly drilled and plugged with short screwable rods and then primed with expoxy and then sand&cement.

Either that or replace the affected damaged block which is not viable in this case.

[George]

Just found this... A common method of repairing delaminating and contour scaling masonry is to 'face up' the defective block with cement mortar. That is not advisable for several reasons:The cement mortar does not replace the load-bearing material that has been lost. Structural failure requires structural repairs, not facing up in cement mortar.The different rate of expansion and contraction between the cement mortar and the sandstone will eventually lead to the two materials separating, a phenomenon referred to as 'bossing' The use of adhesives is sometimes used to strengthen the bond but this often leads to the cement mortar patch pulling part of the sandstone off instead. Water gets trapped behind the cement mortar and accelerates the rate at which the surrounding sandstone decays.If pieces of cement mortar break loose they fall to the ground which causes a hazard to persons directly underneath the building.

[Appin]

The message from "George" contains these words:

Most unlikely.

Of course it can. Cut block out. Redress face. Fill in behind with stone and lime mix. Good as new.

[Appin]

The message from "George" contains these words:

level with the rest of the wall is to use remove all loose and crumbling material and level with lime putty which has none of the problems referred to and does not retain water behind it.