Doors, windows and lintels

Openings for doors and windows interrupt a wall, so the masonry above them must be carried across. A lintel, a beam of reinforced concrete, steel or timber, bridges the opening and rests on the wall at each end with enough bearing, usually at least 150 mm or the lintel depth, to spread its reaction safely.

Masonry above a lintel arches over the opening once the mortar has set. If there is enough wall above and to either side, the lintel carries only the triangle of masonry within a 60 degree line from each support, not the whole height of wall. Loads from floors or roofs that fall inside this triangle, or a short wall height above the opening, mean the lintel must carry more, and the designer must check.

In seismic zones, a continuous reinforced concrete lintel band running around the building at lintel level ties the walls together and replaces separate lintels. Openings should be kept away from corners and limited in total width so that the walls keep enough solid piers to resist shear.

Doors and windows are fixed in frames of timber, steel, aluminium or uPVC, anchored to the masonry with holdfasts or fixings. Sills slope outward and have drips to keep water off the wall; chajjas, small sunshades over windows, protect openings from sun and rain. Sizes follow modular dimensions so that standard shutters fit.