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) sets the structural requirement for buildings in England: loads must be carried safely down to the ground.1 Forming or widening an opening in a load-bearing wall is building work, so it needs either a Building Regulations application with full plans or a Building Notice before work starts.2 Work done without either can only be approved afterwards through a regularisation application to the council, which is slower and may mean opening up finished work.3

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 a roughly triangular zone of masonry above the opening, plus any floor, roof or point load that falls within it, and bearing that load on the solid wall sections on either side of the opening.

The bearing length is the amount of lintel sitting on solid masonry at each end. Approved Document A’s guidance for masonry walls assumes a bearing of 150mm or more, which may be reduced to 100mm where the clear span is 1,200mm or less.1 Longer or heavily loaded lintels are often given 200–300mm. 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 the outer leaf on its toe 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.4 They are normally installed with a cavity tray (a DPC tray) above them, with stop ends and weep holes, so that water crossing the cavity is shed outwards rather than onto the inner leaf; building control will expect to see this as part of meeting the Building Regulations on resisting moisture.4 Some steel lintel profiles are designed to act as their own tray in sheltered and moderately exposed locations, so follow the maker’s instructions.5

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.5

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 conventionally reinforced 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 lintel of 100 × 140mm section weighs about 60kg, which makes handling difficult without equipment.6 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 can carry moderate loads over shorter spans.

Timber lintels are now rarely used in new masonry walls; where timber is encountered during renovation it should be assessed for decay. Decayed or fire-damaged timber lintels are usually 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 WidthTypical Lintel TypeTypical Bearing Each EndTypical Depth
Up to 600mmConcrete or steel (inner), boot steel (external)150mm65–100mm
601–900mmSteel boot lintel (external), concrete (internal)150mm100–143mm
901–1,200mmSteel boot lintel150mm143mm
1,201–1,800mmSteel boot lintel200mm143–219mm
1,801–2,400mmHeavy-duty steel lintel or RSJ with padstones250mm219mm+
Over 2,400mmStructural steel beam (RSJ/UB), engineer required300mm+As specified

For openings over 2,400mm, or where the masonry above carries a floor, roof, or another structural element, a structural engineer should design the lintel (or steel beam) and its supporting structure, and building control will usually ask to see the calculations.

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 TypeSizeApproximate Cost (Supply)
Precast concrete (internal)1,050mm × 100mm£8–£18
Precast concrete (internal)1,800mm × 100mm£20–£35
Standard steel boot lintel1,200mm£30–£55
Standard steel boot lintel1,800mm£50–£80
Heavy-duty steel boot lintel2,400mm£195–£300
Wide-cavity steel lintel1,200mm£45–£75
Padstone (precast concrete)215×102×65mm£3–£8 each
Structural steel (RSJ)Per metre (varies with section)£25–£60/m (supply only)

As a price check, Builder Depot listed an IG heavy-duty 100 mm cavity lintel 2,400 mm long at £196.08 including VAT in October 2026.7 Wade Building Supplies listed the Birtley HD90 heavy-duty cavity lintel in the same length at £302.00.8

As a rough guide, labour for fitting a standard lintel into an existing wall (including temporary propping, cutting, and making good) is commonly quoted at £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 (local authority building control or a registered building control approver reviews plans before work starts, recommended for structural work)
  • Submit a Building Notice (work can start 2 days after the notice is submitted, but plans are not pre-approved, higher risk if something needs to change)3

A Completion Certificate is issued when the work passes inspection.3 This is essential for conveyancing, solicitors routinely ask for it when a property is sold.

When you will normally need a structural engineer:

  • 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 cover planning only; they do not override the need for Building Regulations approval.9 A replacement window in an unaltered opening is normally self-certified by an installer registered with a competent person scheme such as FENSA, but any change to the opening size in a load-bearing wall needs building control.9

References (9)

Figures in this note were checked against the sources below on 6 October 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.

  1. 1technicalvery strongMinistry of Housing, Communities and Local Government (GOV.UK).RN-Z6AXUWThe full Approved Document A PDF, which carries the deemed-to-satisfy tables a domestic project is checked against. Section 2E covers foundations of plain concrete: paragraph 2E3 gives the recommended minimum widths of strip foundations in Table 10, keyed to ground type and total load of loadbearing walling per linear metre. Table 10 sets, for rock (not inferior to sandstone, limestone or firm chalk, requiring at least a pneumatic or mechanically operated pick to excavate), a width equal to the width of the wall at every load. For medium dense gravel or sand (requires a pick to excavate, a 50mm square wooden peg hard to drive beyond 150mm) and for stiff clay or stiff sandy clay (can be indented slightly by the thumb), the minimum widths are 250mm at 20 kN per linear metre, 300mm at 30, 400mm at 40, 500mm at 50, 600mm at 60 and 650mm at 70. Firm clay and firm sandy clay (thumb makes an impression easily) start at 300mm. The document also covers minimum depth of strip foundations, wall thickness rules for residential buildings up to three storeys (paragraph 2C10 covers internal loadbearing walls in brickwork or blockwork), buttressing, lateral support by floors and at roof level, interruption of lateral support, wall cladding in Section 3, and Section 5 on reducing sensitivity to disproportionate collapse with the building consequence classes.
  2. 2technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-37ODVXRegulation 12(1) applies to anyone intending to carry out building work, replace or renovate a thermal element, change a building's energy status or make a material change of use. Regulation 12(2) requires that person to give the relevant authority either a building notice under regulation 13 or an application for building control approval with full plans under regulation 14. Full plans are compulsory where the Regulatory Reform (Fire Safety) Order 2005 applies (12(3)), where the building fronts onto a private street (12(4)) and where paragraph H4 of Schedule 1 applies (12(5)). Regulation 12(6) exempts work done by a competent person listed in Schedule 3, work listed in Schedule 4, and work inspected by a Schedule 3A third party certifier appointed before work starts. Regulation 12(6A) still requires notification for Part P electrical work consisting of a new circuit, a consumer unit replacement, or any addition or alteration to existing circuits in a special location such as the zone around a bath or shower. Regulation 12(8) allows a building notice after the event for emergency repairs. Text is up to date to 7 September 2026.
  3. 3technicalvery strongGOV.UK, a government page.RN-JYRZYTHow to get building regulations approval: the choice between a full plans application and a building notice, using a competent person scheme instead where the work qualifies, and the determination and appeal routes if approval is refused. This is the page that decides which route a job takes, and the route decides both the fee and how much can go wrong on site before anyone checks.
  4. 4technicalsupplier figureBritish Board of Agrément (published by Catnic), guidance.RN-YA60KPThe BBA certificate for Catnic's heavy and extra heavy duty cavity lintels. It specifies hot-dip galvanised steel to BS EN 10346 with Z275 or Z600 coatings and a polyester powder finish.
  5. 5technicalsupplier figureCatnic (Tata Steel UK), guidance.RN-OITPGSCatnic's lintel product selector brochure. It states the company has made steel lintels for over 50 years and gives its ranges, weights and installation guidance.
  6. 6technicalsupplier figureStressline Limited, guidance.RN-Q5WZVIA prestressed lintel maker's load-span data sheet. It gives 15.3 kg per metre for the 100 x 65 lintel, so about 18 kg for a 1.2 m unit.
  7. 7technicalsupplier figureBuilder Depot, guidance.RN-PDF2TTBuilder Depot product page for the IG L1/HD 100 heavy-duty cavity lintel, 2,400 mm long, at £196.08 including VAT: the low end of the corrected 2,400mm heavy-duty row.
  8. 8technicalsupplier figureWade Building Supplies, guidance.RN-BYGOQIWade Building Supplies product page for the Birtley HD90 heavy-duty 100 mm cavity lintel, listing the 2,400 mm length at £302.00 including VAT: the top of the corrected row.
  9. 9technicalvery strongGOV.UK, guidance.RN-81EIUNThe government's own list of alterations that need building regulations approval, and the page to cite when a reader asks whether a bathroom or kitchen refit is notifiable. Works listed as needing approval include installing a bathroom that will involve plumbing, changing electrics near a bath or shower, replacing a fuse box and connected electrics, replacing windows and doors, replacing roof coverings, installing or replacing a heating system, adding radiators to an existing heating system, and installing fixed air conditioning. Emergency repairs to a boiler or heating system do not need approval in advance, though specific rules then apply. Approval may be obtained from a local authority building control department, a private registered building control approver, or, for higher-risk residential buildings, the Building Safety Regulator. The page states the practical consequence bluntly: without approval you will not have the certificates of compliance you may need when you want to sell your home. Note that a like-for-like bathroom refit with no new plumbing, no drainage change and no work in the electrical zones is not on the list.

  1. Approved Document A, Structure, 2004 edition incorporating 2004, 2010 and 2013 amendments, Ministry of Housing, Communities and Local Government, accessed 14 September 2026. assets.publishing.service.gov.uk

  2. The Building Regulations 2010, regulation 12: Giving of a building notice or an application for building control approval, The National Archives, accessed 30 September 2026. legislation.gov.uk

  3. Building regulations approval: How to apply, GOV.UK, accessed 30 September 2026. gov.uk

  4. BBA Agrément Certificate: Catnic CH and CX Range of Cavity Wall Lintels, British Board of Agrément (published by Catnic), accessed 30 September 2026. catnic.com

  5. Catnic Lintel Product Selector (June 2024), Catnic (Tata Steel UK), accessed 30 September 2026. catnic.com

  6. Prestressed Concrete Standard Lintels: load-span tables, Stressline Limited, accessed 30 September 2026. stressline.net

  7. IG L1/HD 100 90-105mm Heavy Duty Cavity Lintel 2400mm, Builder Depot, accessed 6 October 2026. builderdepot.co.uk

  8. Birtley HD90 Heavy Duty 100mm Cavity Lintel, Wade Building Supplies, accessed 6 October 2026. wadebuildingsupplies.co.uk

  9. Building regulations approval, GOV.UK, accessed 30 September 2026. gov.uk