Step One: Wall Construction – How is the wall constructed?
Cavity Wall: Measure the inner leaf thickness, cavity width & outer leaf thickness. Birtley recommends the use of an additional cavity tray with all external cavity wall lintels.
Solid Walls: Available for Single leaf face brick or block external walls. 200-215mm solid brick or block walls. 215mm fair face solid walls with two leaves.
Internal Walls: Available for Loadings from floor joists and blockwork, point loads and wide openings and non-load bearing walls.
Timber Frames: Measure the cavity width & the outer leaf thickness.
Step Two: Opening – How wide is the opening?
Measure: The opening that will contain the window or door.
The Lintel: Should be minimum 300mm wider than the opening (150mm at each end)
HDX Lintels: Should be 400mm wider (200mm at each end)
Birtley lintels are classified as standard, medium, heavy & extra heavy duty. Each category has a designated safe working load (SWL) measured in kilonewtons (kN) which must not be exceeded.