Lintel

A lintel is a horizontal beam that sits above a window or door opening, supporting the weight of the wall, roof, or floor above and directing that load to either side of the opening. Without a lintel, the masonry above a window or door would collapse into the gap. Every window and external door in your home has a lintel above it — even if you can’t see it behind the plaster or render.

Types of lintel

Steel lintels

The most common type in modern construction:

• Made from galvanised or stainless steel, formed into a specific profile
• Lightweight and easy to install
• Available in standard lengths for common opening widths
• Some include an insulation layer to prevent cold bridging

Concrete lintels

Heavy, solid beams of reinforced concrete:

• Very strong and durable
• Common in older properties and for heavy loads
• Heavier to handle — may need lifting equipment for larger sizes
• Can be pre-cast (made in a factory) or cast in place on site

Stone lintels

A single piece of stone spanning the opening:

• Found in older and period properties
• Can crack or fail over time, especially if the stone is soft
• Replacement usually requires a matching stone for conservation purposes

Timber lintels

Wooden beams used in older construction:

• Common in pre-Victorian properties
• Susceptible to rot and woodworm
• Often discovered during renovation when plaster is removed — a failed timber lintel is a common surprise that eats into your contingency

When lintels matter in renovation

Lintels become a key concern when you’re:

• Creating new openings — cutting a new window or door into an existing wall requires installing a new lintel
• Widening existing openings — making a window bigger or combining two openings into one means the existing lintel must be replaced with a wider one
• Discovering failed lintels — cracked or corroded lintels are often found when walls are stripped back to brick during renovation
• Installing bifold or sliding doors — wide openings require substantial lintels (or RSJs for very large spans)

Lintel vs. RSJ

A lintel spans a relatively small opening (typically up to about 3 metres). For larger openings — like removing a load-bearing wall to create an open-plan space — a much larger structural steel beam (an RSJ) is used instead. The structural principle is the same: supporting the weight above an opening.

Do you need building regulations approval?

Yes. Installing or replacing a lintel is structural work and requires building regulations approval. A structural engineer may need to calculate the correct size, and building control will want to inspect the installation before it’s concealed behind plaster.

Tips for homeowners

• Never remove or modify a lintel without professional advice — it’s supporting the structure above
• Budget for lintel surprises — especially in older properties where timber lintels may have deteriorated
• Decide on window and door sizes early — lintel size depends on the width of the opening, so changes later can mean new structural calculations
• Take photos before plastering — as with all structural work, photograph the lintel installation for your records