Screed

Screed is a mix of cement, sand and fine gravel spread over a roof slab or a floor. Greek builders often just call it the "filling". On roofs, lightweight concrete is also used, which weighs less.

It has two jobs: to give the surface the right falls towardsFalls (drainage slope)The gentle slope built into flat roofs, balconies and bathroom floors so water runs to the drain or gutter instead of pooling. the drainsFloor drainThe outlet in a floor where water drains away on roofs, balconies and in bathrooms, with a grate on top and usually a trap below., so water doesn't pool, and to cover and protect the insulationThermal insulationA layer of material that lets heat through only slowly, so a home keeps its warmth in winter and stays cool in summer. underneath, giving a floor that can be walked on. On large areas it is pumped up to the roof and levelled with a straightedge.

Screed is not waterproofingWaterproofingThe work and materials that stop water getting through on flat roofs, balconies, bathrooms, basements, planters and tanks.: cement cracksCrackA split or gap in render, concrete, a wall, a coating or wood. Fine cracks are usually only on the surface; ones that grow, keep reopening or run diagonally need attention. and soaks up water. It also has to dry out properly before any waterproofing goes on top, or the trapped moisture pushes up blisters.