The brick wall at the end of my garden is probably about 200 years old and the faces of the bricks are quite crumbly and powdery. The wall is quite solid in spite of its age but I would like to seal the external surface to prevent further wearing away. Would it be better to use a thinned PVA adhesive or a waterproof sealer? I don’t think that it needs waterproofing as much as stabilising the surface of the bricks. Yes, rebuilding would be the real solution but there would be too many zeros after the number.