How Much Weight Can a Concrete Lintel Support?

How much weight a concrete lintel can support is determined by two main factors, the height of the lintel, and the amount of reinforcement embedded within. The narrower an opening, the smaller the lintel needs to be.

Concrete lintels, made with reinforcing bars, and a dense cementitious mix can be used from foundation level over service entryways, up to roof level. So how do you work out which lintel is the right one for the job at hand?

Some projects will require specialist knowledge, perhaps a referral to a structural engineer, but, in general, there are a few things to remember when deciding which specification is the right one.

What Can a Concrete Lintel Support?

Measured in Kilo-Newtons per Metre, a lintel load table will tell you how to calculate how much weight a metre length of a particular lintel is able to support.

How Big a Lintel Do You Need?

A problem with understanding many lintel tables is that they seem to be put together for engineers with their references to shear capacities and moments of resistance.

At the end of the day, the number that really matters is the safe working load or the minimum allowable load, which is usually entered in the last column in the table.

An important consideration is that internal masonry leaves in a cavity wall take larger loads, such as floor joists, or rafters than external leaves. This means that there will often be a difference between the inner and outer lintel.

Triangulation of Lintel Load

This is simpler than it looks too. Imagine a triangle above the lintel. This is the masonry load, and other items directly supported by the concrete lintel.

For an opening a metre wide, the triangle will start at the ends of the lintel, so will be 1.2m wide at the base. The lintel will be directly supporting just over 0.6 square metres of masonry.

For an opening which is 3.2m wide, the base of the triangle will be 3.6m wide and support almost 4.5 square metres of masonry.

For Smaller Openings

For example, a 100mm concrete lintel used over a 1000mm opening, with a minimum bearing of 100mm to each side (making a lintel 1200mm long), will be able to support up to 8.86 kN/m.

But what does that mean in simpler terms?

A standard pallet of about 500 bricks weighs in at approximately 19 kN, and a square meter of bricks will use up to 60 bricks in total.

An average brick wall weighs in at about 5.5 kN per square metre, which means that a P100 will be well within safe limits in this case.

For Larger Openings

The limits for lintels are expressed per metre span of an opening. It’s worth noting also, that the wider an opening, the bigger the bearing will be required at each end.

For a 3.2m opening, a bearing of 200mm will be required, so a 3.6m lintel is needed to provide sufficient support. The R9 concrete lintel from Naylor can support up to 8.36 kN/m.

On an average masonry wall, the approximate load of 5.5 kN per metre will mean that each metre of the lintel will support 7.73 kN, which is within safe limits.

How Do Concrete Lintels Differ?

The P100 lintel is a single-strand steel reinforced item whereas the R8 contains three steel tendons and is wider as well as taller.

As a general rule, the more steel within a concrete lintel, the more weight it can support. The steel is usually set in the lower section of the lintel too, whether a lintel is 140mm high, or 290mm high.

Concrete lintels can be cut to fit, but any exposed steel reinforcement should be protected with mortar or concrete.

Why Use a Concrete Lintel?

Concrete lintels are cost-effective, single-leaf support options for many masonry wall applications.

Below Ground

Concrete lintels are excellent for use below ground level where a drainage pipe exits a building, or where services enter. A concrete lintel, with the proper level of cover to each end, will not suffer from exposure to water or damp.

As long as the reinforcement is not exposed, then a concrete lintel will outlast any other means of below-ground support.

Doors and Windows

For fair-faced blockwork or render finishes, a concrete lintel will give continuity of surface finish. Both render and plaster will adhere to concrete, so where masonry is used to build internal walls, as soon as the mortar is cured, you’re ready to go.

Concrete lintels can span from 700mm up to 3.2 metres and can come fire-rated and tested for resistance to chemical attack too.

Standard, Live, and Imposed Loadings

Standard loadings are straightforward and can be worked out using the simple strategy outlined above. However, when it comes to more complicated factors, such as the installation of an opening below joist bearings, or adjacent to a staircase, then things can get a little more complex.

For expert advice, don’t hesitate to get in touch with our team at Wade who are well-placed to help.