Stressline composite lintel

Lintel application: A builder’s guide

Marketing ALL, Concrete Lintels, Specification, Steel Lintels 7 Comments

Our builder’s guide to lintel application comes off the back of some very popular blog posts. Here we want to help those of you in the trade understand a little more about how our lintels can be and are used. The basic application is simple enough, but there is more to consider than you might think.

Concrete and steel lintels

Standard cavity lintel

Steel lintels are generally used for cavity openings on the outer envelope

One of the first considerations is which material is used. This will of course depend, on what you want to use the lintel for. Steel lintels are often cavity lintels and therefore used on the outer envelope of the build. Concrete lintels are often found inside the build, but there are specific reasons to specify concrete lintels. Find out more about prestressed concrete lintels vs. steel lintels.

Lintel selection

Selecting the correct lintel is dependent upon a number of factors; wall construction, cavity width, opening width, and load. You can read more about lintel selection here.  One aspect to have an appreciation of is the load triangulation. This looks at the load above the lintel and incorporates the masonry, roof loads, floor loads and point loads.

Standard and HD variants

Most types of lintels on offer have an HD (heavy duty) variant available. These are manufactured to a general specification and have higher load bearing capabilities. The HD and XHD (extra heavy duty) lintels are generally used for concrete floor loads, attic truss loads and some point loads.

Composite or combined lintel

Steel composite lintel

Composite lintels are some of the strongest lintels available.

What is the difference between a combined and composite lintel? In a nutshell, a combined lintel uses two structural elements (like a steel single leaf lintel on the outer leaf, and a high strength concrete lintel on the inner leaf.) A composite lintel is one structure that uses a ‘composite action’ to create an ultra HD lintel with considerably higher load bearing capabilities. Each product group in our standard range has composite lintels (CXHD) available. You can read more about combined lintels and composite lintels here.

Insulation and thermal bridging

Steel lintels have polystyrene between the upstand sections of the lintel to create thermal efficiency. On our own steel lintels, the poly inner is wedged and glued in place to ensure that it remains in place throughout the build process. Some ‘thermal break’ lintels are available which are designed to further reduce the thermal bridge and increase thermal efficiency. A popular alternative is a combined lintel (see above) which offers exceptional thermal efficiency by way of removing the bridge between the inner lintel and outer lintel altogether.


Installing a lintel can be very easy especially when the opening is small and you know there is little load to bear onto the lintel. However, it can quickly become a little trickier when the opening is bigger, and when you have to consider things like point loads. A general rule of thumb is to have 150mm bearing on each side, and we would recommend using padstones in most circumstances. You can read more installation tips here.

Comments 7

  1. Hello, I’m undertaking an extension at home and I need to clarify with the building inspector the correct use of one of your lintels please. I’m installing 4200mm bifold, top hung doors. It is solid 4N aerated blockwork. The outer box lintel is a stress line HD 220mmx100mm galv box lintel with a stressline galv angle bolted to it. The grp flat roof above is 4.4m wide and will be supported by the lintel at one end and a wall plate at the other. The lintel weighs 80kg with the angles. A 350mm high parapet wall will also be supported by the lintel. 2no. 2mx1m flat roof lights will also be in the roof and the lintel will support 2 of the double trimmers.

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  2. hi
    I have a 3m opening for 3m bi fold door. can you advise me what lintel I would need please. your answer urgently would be greatly appreciated.thanks

  3. I have two bi folds to fit, one 5m and one just over 2m. The window co state deflection can’t be greater than 1 ? Over any meter length, therefore 5 and 2. The structural engineering has calculated deflection at 13.24, making it impossible to fit the windows. Please can you let me know if there are any steel beams wit( zero deflection. Perhaps I also need steel uprights nex5 to the bifold. I am new to this, but learning by the day!

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      Hi, thanks for your question.
      The allowed deflection is (lintel length(mm) – 150mm)/325mm, however, this, as you point out, is not always acceptable for bi-fold doors. We tend to recommend RS lintels for bi-fold doors because of this problem, and certainly, when installing them, they will need to be adequately propped. If you download our lintel guide, the technical section at the back gives more details about installation. Thank you.

  4. Hi, I need a lintel to fit above a new window in a bedroom. The window is 1200mm wide and the wall type is a solid external, load bearing wall. Any advice is useful. thanks

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