Sandstone varies dramatically in its porosity – you can apply certain Sandtex Trade products but you will need to check if the surface is sandy and quite porous, if this is the case then you will need to treat the area with Sandtex Trade Stabilising Solution first and then with a topcoat for example Sandtex Trade High X-posure Smooth or Sandtex Trade High Cover Smooth. You could also use the new Sandtex Trade Hydrobond – a product specifically designed to be used on problem substrates that require exceptional adhesion.