Waterproofing old roughcast

[dieselpower]

As opposed to chipping off old roughcast which is quite porous, does anyone on here recommend anything to put over the top of it to seal it and make it watertight? thanks in advance..

 

[Render Systems]

water seal
Thompson's Water Seal | Screwfix.com

 

[warriorupnorth]

They do a version of this for walls, good stuff and still breathable apparently
Low Solid Sealer: Pattern Imprinted Concrete Supplies