A lintel is a structural beam placed over a door, window, or other opening in a wall to carry the load of the structure above and transfer it to the masonry on either side. Without one — or with one that is undersized — the masonry above the opening will crack, arch, or eventually collapse. Getting the lintel specification right is one of the non-negotiable structural decisions in any renovation involving new or widened openings.
Building Regulations Part A (Structure) governs structural integrity in England and Wales. Any work involving lintels in a load-bearing wall requires either a Building Regulations application or a Building Notice before work starts — it cannot be signed off retrospectively in a straightforward way.
What a Lintel Does
When you cut an opening in a wall, you interrupt the load path from the structure above. The lintel acts as a bridge, collecting the load from the masonry triangle above the opening (the load-bearing zone extends at roughly 45° from each jamb upward) and bearing that load on the solid wall sections on either side of the opening.
The minimum bearing length — the amount of lintel sitting on solid masonry at each end — is 150mm for spans up to 1,200mm, and 200–300mm for larger spans. Your structural engineer or Building Control officer may specify greater bearing for heavily loaded situations. Padstones (flat concrete or engineering brick blocks) distribute the point load at the bearing point when the masonry would otherwise be overstressed.
Types of Lintel
Steel Boot Lintel (Cavity Wall Lintel)
The standard choice for modern UK cavity wall construction (a wall with an inner leaf, cavity, and outer leaf). The “boot” profile wraps around the bottom of the outer leaf, carrying both the outer (structural) leaf and bridging the cavity to support the inner leaf. A single boot lintel does the job of two lintels in one component.
Steel lintels are galvanised (and sometimes additionally coated) to resist corrosion. They must be installed with a DPC (damp-proof course) tray above them to prevent water tracking from the outer leaf through the cavity — this is a Building Regulations requirement.
Common profiles include: single-leaf (for solid walls or the inner leaf only), dual-leaf (standard cavity boot lintel), and wide-cavity versions for 100mm+ cavities used in modern energy-efficient construction.
Concrete Lintel
A precast concrete lintel is the most economical option for internal openings and for the inner leaf of a cavity wall where a steel boot is used on the outer. Prestressed concrete lintels (with reinforcing wires) span further than plain concrete lintels of the same depth.
Concrete lintels are durable, fire-resistant, and available off the shelf from builders’ merchants. They are heavy — a 1,800mm concrete lintel can weigh 60kg or more — which makes handling difficult without equipment. Not suitable as the sole lintel over external cavity wall openings.
Timber Lintel
Timber was the traditional lintel material for smaller openings in older UK housing stock. Victorian and Edwardian houses commonly have timber lintels over door and window openings, particularly in internal walls. A solid hardwood or softwood timber lintel (usually oak or Douglas fir) can carry moderate loads over shorter spans (typically up to 1,200mm).
Timber lintels are not used in new construction for structural roles in external walls; where timber is encountered during renovation it should be assessed for decay. Exposed or fire-affected timber lintels should be replaced with steel or concrete equivalents.
Padstones
A padstone is not a lintel but works in conjunction with one. It is a flat block — typically engineering brick, precast concrete, or dense natural stone — placed under the end of a lintel to spread the concentrated point load over a larger area of masonry. Padstones are typically required when:
- The lintel bears on a single course of brickwork over another opening
- The masonry beneath the bearing point is weak or hollow (e.g., a lightweight blockwork inner leaf)
- A structural engineer specifies them for a heavily loaded situation
Standard padstone sizes: 215×102×65mm to 440×215×150mm, depending on load and specification.
Sizing Rules
The span of a lintel is the clear width of the opening. The lintel length must be:
Lintel length = Opening span + (2 × bearing length)
For a standard 900mm doorway with 150mm bearings each end: Lintel length = 900 + 150 + 150 = 1,200mm
For a 2,400mm opening (double doors) with 300mm bearings: Lintel length = 2,400 + 300 + 300 = 3,000mm
Lintel depth (height of the section) increases with span and load. Manufacturer span tables are the definitive reference — each lintel product is load-rated at specific spans. A structural engineer will specify the exact product reference for non-standard or heavily loaded situations.
Lintel Sizing by Opening Width
| Clear Opening Width | Typical Lintel Type | Minimum Bearing Each End | Typical Depth |
|---|---|---|---|
| Up to 600mm | Concrete or steel (inner), boot steel (external) | 150mm | 65–100mm |
| 601–900mm | Steel boot lintel (external), concrete (internal) | 150mm | 100–143mm |
| 901–1,200mm | Steel boot lintel | 150mm | 143mm |
| 1,201–1,800mm | Steel boot lintel | 200mm | 143–219mm |
| 1,801–2,400mm | Heavy-duty steel lintel or RSJ with padstones | 250mm | 219mm+ |
| Over 2,400mm | Structural steel beam (RSJ/UB) — engineer required | 300mm+ | As specified |
For openings over 2,400mm, or where the masonry above carries a floor, roof, or another structural element, a Registered Structural Engineer must design the lintel (or steel beam) and its supporting structure. This is non-negotiable under Part A.
Load Categories
Lintels are rated for different load scenarios:
Internal partition wall — carries only the weight of the masonry above (light load). A standard internal concrete lintel is usually adequate.
External cavity wall (below roof level) — carries the outer leaf masonry plus cladding, and the inner leaf plus plasterboard. Moderate load; a standard boot lintel to the manufacturer’s span table.
External wall below a floor — the lintel must carry the floor load in addition to the masonry above. Heavier load category; check manufacturer tables specifically for floor load conditions.
Structural opening (removing a wall between rooms) — may involve carrying a floor or roof load. Requires a structural engineer’s calculation and specification; may require a steel beam (RSJ or universal beam) rather than a standard lintel.
Costs (UK, 2026)
| Lintel Type | Size | Approximate Cost (Supply) |
|---|---|---|
| Precast concrete (internal) | 1,050mm × 100mm | £8–£18 |
| Precast concrete (internal) | 1,800mm × 100mm | £20–£35 |
| Standard steel boot lintel | 1,200mm | £30–£55 |
| Standard steel boot lintel | 1,800mm | £50–£80 |
| Heavy-duty steel boot lintel | 2,400mm | £80–£130 |
| Wide-cavity steel lintel | 1,200mm | £45–£75 |
| Padstone (precast concrete) | 215×102×65mm | £3–£8 each |
| Structural steel (RSJ) | Per metre (varies with section) | £25–£60/m (supply only) |
Labour for fitting a standard lintel (including temporary propping, cutting, and making good) typically ranges from £300–£800 per opening depending on complexity, access, and whether the existing lintel is being replaced or a new opening is being formed.
Building Regulations and Building Control
Any work forming or widening an opening in a load-bearing wall requires Building Regulations compliance under Part A (Structure). You must either:
- Submit a Full Plans application (the LA Building Control or an Approved Inspector reviews plans before work starts — recommended for structural work)
- Submit a Building Notice (work can start 48 hours after notification, but plans are not pre-approved — higher risk if something needs to change)
A Completion Certificate is issued when the work passes inspection. This is essential for conveyancing — solicitors routinely ask for it when a property is sold.
When a structural engineer is required:
- Any opening wider than 1,800mm in a load-bearing external or party wall
- Any opening where a floor, roof truss, or beam bears directly above
- Removing a load-bearing internal wall (even if the lintel itself is a standard product, the calculation must be signed off)
- Underpinning or altering foundations to create a basement opening
Permitted Development rights do not override the need for Building Regulations approval. A new window in an existing masonry opening of the same size may not trigger a full application, but any change to the opening size in a load-bearing wall does.
