PT-06Prepare and paint solid masonryFor an internal brick or block wall with no plasterboard, check first for damp or loose, crumbly render, since paint will not fix that. If it's sound, a mist coat works the same way as on plasterboard for a very absorbent wall, otherwise go straight to emulsion. For an exterior masonry wall, use a proper breathable masonry paint, never ordinary indoor emulsion, which will trap moisture and blister.