Make sure the surface is dust free before application
Growths of fungus, algaes or moss should be removed by wire brushing and water
Any surface cracks or holes should be raked out and filled with Duracoat Internal & External Skimcoat
Treat surface for moulds and algaes if present with Duracoat Fungicidal Wash.
On exceptionally porous surface apply one coat of Duracoat Acrylic Sealer. Make sure the surface is dust free before application. Allow overnight drying before applying a second coat of the same.