Primer

Primer is a thin material applied first, on a clean surface. It soaks into the pores of concrete, renderRender (plaster)A layer of mortar (sand, cement or lime, and water) spread over brick or concrete to give a wall a straight, sound surface ready for paint or tiles. or wood, binds any remaining dust and evens out how absorbent the surface is. That way the next material bonds firmly and dries the same everywhere.

Each material needs its own primer. On flat roofsFlat roof (roof terrace)The flat concrete roof on top of a building. It is the most common kind of roof in Greece and the part that takes the most sun and rain. a bitumen or polyurethane primer often goes down before foamSpray polyurethane foamA foam sprayed on as a liquid that expands on the spot and sets into one seamless layer. It insulates against heat and cold and closes cracks and joints. or a membrane, on walls an acrylic primer goes on before paint, and on wood a primer made for wood. The right choice depends on the surface and on what goes on top.

Because primer is invisible at the end, it is the step most easily skipped. Without it, though, paint comes out patchy and waterproofingWaterproofingThe work and materials that stop water getting through on flat roofs, balconies, bathrooms, basements, planters and tanks. can come loose early. It also has to dry for as long as the manufacturer specifies before the next coat goes on.