A cavity wall lintel is a structural support placed above an opening, such as a window or door, in a cavity wall. It spans both the inner and outer leaf of the wall, carrying the load above and transferring it safely to the surrounding masonry.
Unlike standard lintels used in solid walls, cavity wall lintels are designed to support two separate leaves while maintaining the cavity between them. This is critical for both structural stability and moisture control in modern UK construction.
- Supports brickwork and blockwork above an opening
- Spans both inner and outer leaves of a cavity wall
- Prevents loads transferring onto window or door frames
- Maintains the cavity for insulation and moisture control
If you're new to lintels more broadly, you may want to read our complete guide to lintels in the UK, which explains the different types and where they are used.
What is a cavity wall lintel?
A cavity wall lintel is specifically designed for walls made up of two layers, typically an inner block leaf and an outer brick leaf, separated by a cavity. This type of wall construction is standard in most modern UK homes.
The lintel sits above openings such as windows and doors, supporting the masonry above and ensuring that the weight is distributed safely into the surrounding structure.
Because there are two separate leaves, the lintel must support both independently while keeping the cavity clear. This is what differentiates it from a standard solid wall lintel.
How cavity wall lintels work
On site, a cavity wall lintel is effectively doing two jobs at once.
It supports the outer leaf (usually brickwork), which is exposed to weather, and the inner leaf (typically blockwork), which carries internal loads. These loads are transferred through the lintel and into the masonry on either side of the opening.
The key detail is that the cavity between the two leaves is maintained. This gap plays an important role in preventing moisture transfer and improving thermal performance.
Most modern cavity lintels are designed with a profile that separates these two load paths while also allowing for insulation and damp-proofing elements to be integrated.
If the wrong type of lintel is used, loads may not be properly supported, or the cavity may be bridged. This can lead to structural issues, cold bridging, or moisture problems over time.
Types of cavity wall lintels
There are several types of cavity wall lintels used in UK construction, depending on the wall build-up and loading requirements.
Standard cavity lintels are the most common and are designed for typical domestic openings.
Heavy duty lintels are used where loads are higher, such as wider openings or additional masonry above.
Thermally broken lintels include an insulating section to reduce heat loss through the lintel. This is increasingly important in modern builds and renovations aiming to improve energy efficiency.
If you're unsure how thermal breaks work, see our guide on what a thermal break is.
In the UK, cavity lintels are commonly supplied by manufacturers such as Stressline, Catnic, and Birtley, each offering different profiles and load capacities.
What do building regulations require?
Cavity wall lintels must be suitable for the loads they carry and the wall construction they are used in. In the UK, they are typically designed in line with standards such as BS EN 845-2 (lintels) and Eurocode guidance for masonry structures.
Building control will usually be looking for:
- Correct lintel type for the wall construction
- Adequate bearing on each side of the opening
- Proper support of both inner and outer leaves
- Integration with damp proof courses (DPC) and cavity trays where required
In practice, this means the lintel must match both the structural and environmental requirements of the wall.
Lintel selection should always be based on the specific opening and load conditions. Where there is any uncertainty, manufacturer guidance or structural input should be followed.
Where are cavity wall lintels used?
You will typically find cavity wall lintels used above:
- Windows
- External doors
- Patio and bifold door openings
- Garage door openings
They are standard in most modern housing and are also used in extensions and renovations where cavity wall construction is present.
How loads are supported
The load carried by a lintel depends on what sits above it, which may include masonry, floors, or roof structures.
While this article focuses on how cavity lintels work, if you're interested in how load is calculated in more detail, see our guide on how much weight a steel lintel can support.
In most cases, the key principle is that the lintel transfers load to the masonry on either side of the opening, provided there is sufficient bearing.
Choosing the right lintel
Choosing the correct cavity wall lintel depends on several factors, including the width of the opening, the wall construction, and the load above.
Rather than guessing, it is important to follow manufacturer load tables or seek guidance where needed.
If you're looking to explore available options, you can browse our full range of lintels here.
For a broader overview of lintel types and applications, see what a lintel is and the different types available.
