Crack

Cracks have many causes. 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. and concrete shrink as they dry, materials expand in the heat and contract in the cold, and buildings move slightly over time. Cracks open most easily where different materials meet, such as between brick and a concrete column or between a new and an old wall; that is why reinforcement meshReinforcement meshA mesh or fabric, usually glass fibre or polyester, set into render, a coating or liquid waterproofing to hold it together and stop cracks from opening. is set into the render or coating there.

Most cracks are hairline and only on the surface. They are opened up slightly, filled with the right material (fillerFillerA fine paste or powder that fills holes, fine cracks and dents so a wall, ceiling or piece of wood is smooth before it is painted., repair mortarRepair mortarA special cement-based mortar for rebuilding concrete that has cracked or fallen away, for example around rusty steel. It bonds well to old concrete and seals the reinforcement in. or a flexible sealant, depending on where they are) and painted. On roof terracesFlat 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. and balconies, though, even a small crack is a way in for water and has to be sealed before waterproofingWaterproofingThe work and materials that stop water getting through on flat roofs, balconies, bathrooms, basements, planters and tanks..

Some cracks point to something deeper. Straight-line cracks in a ceiling or column, with rust showing, can mean rebarRebar corrosionRust on the steel bars inside concrete. Rusting steel swells, cracks the concrete around it and makes it fall away in pieces, leaving the bars exposed. corrosion. Diagonal cracks running from the corners of doors and windows, or cracks that keep growing, may have a structural cause. Then the crack is not just filled; an engineer needs to look at it.