UK Lintel Sizes — Steel & Concrete

The minimum end bearing for lintels in masonry is 150 mm on each side of the opening. This is a Building Regulation requirement under Approved Document A. For spans over 3 m, some manufacturers require 200 mm bearing. The bearing surface must be solid — a full block or brick, not cut pieces. Padstones may be required for point loads on blockwork.

Steel lintels are lighter, easier to handle and available for cavity walls in one piece. They are the standard choice for most domestic openings up to about 4.8 m. Concrete (prestressed) lintels are heavier but cheaper for simple openings and are more common in inner-leaf or solid wall applications. For wide openings or heavy loads, structural steel beams (RSJs) may be needed with a structural engineer calculation.

Steel cavity lintels are made for specific cavity widths. Common sizes are 50 mm, 65 mm, 75 mm, 90 mm and 100 mm cavity. The lintel cavity must match your wall cavity width. Partial fill insulation may sit within the lintel tray. Full-fill cavities typically use a wider lintel. Always check the manufacturer range for your exact wall build-up.

Steel cavity wall lintels typically have an integral DPC tray. Concrete lintels in cavity walls need a separate cavity tray DPC installed above them to direct any moisture in the cavity outward through weep holes. Weep holes should be provided at maximum 450 mm centres along the outer leaf above the lintel.