A lintel is a lintel is a lintel right? Well not quite. Yes, the job of the lintel is pretty straight forward in that it has to bear a load, but not all lintels are the same, and there are many different types of lintels designed to do different things.
From a specification point of view, there is a multitude of applications and a number of considerations you need to think about, which is where we will start.
Things to consider when specifying lintels
Understanding load span tables, and load ratios is a good idea for those who are specifying lintels.
Fundamentally there are two main things that specifiers have to consider when choosing a lintel a) the load it has to bear and b) the length of the opening; these two characteristics alone create a multitude of lintel options, but there are other things to consider, as well as being able to calculate the correct load, and therefore select the correct lintel.
In terms of the load, you will have to consider the load of the masonry, the floor load, the roof load and consider the load ratio (how the load is split between the inner leaf and outer leaf).
As well as the length of the opening, you may need to think about the shape; if it is a bay window for example.
The location of the opening also needs consideration. If the opening is on the outside of the building – is there a cavity wall? What is the depth of the cavity? If the opening is below ground, what lintel will you choose? Will the exposure to moisture mean a concrete lintel?
The wall construction also needs consideration, a timber frame will need a specific lintel, as well as the thickness or widths of the walls – will this affect the leaf size of the lintel?
Finally, other considerations like the thermal properties will come into play. There may be some cases where you need to know the thermal properties of the lintel, and are looking for a thermally effective lintel for a specific project.
General applications
Timber frame lintels are used for a specific purpose and are designed with no inner leaf.
The general application for a lintel is to bear the weight of a load constructed above it. Standard cavity lintels are often specified for the outer envelope of a property and they are designed to be used within brickwork, so as little of the lintel is showing as possible.
Variations of this will depend on the leaf sizes required. A short outer leaf lintel (SOL) for example could be used when you have cant brick or certain decorative detail above the window.
Specific applications
Some lintels are designed with a specific use in mind and are specified for very little else. Closed eave lintels are designed to be used in the eaves of buildings where the entire load is impacting on the inner leaf only, and no load is bearing onto the outer leaf. This is where knowledge of the load ratios comes in handy.
Timber frame lintels are designed to be used with timber frame buildings, obviously and have no inner leaf.
Rolled steel lintels are for use with extreme loading conditions, and would not be specified for standard 1200mm windows.
Multiple applications
Stressline box lintels can be used for a number of applications.
Some lintels can be used in a variety of ways, for different tasks. Fair faced lintels not only bear loads of the construction above but are finished in a way to ensure they can be visible.
Box lintels are also useful as they can offer good load bearing capabilities and can be used at various levels with various loading conditions.
Some tray and channel lintels can also be used with other products to ensure a certain finish or addition to thermal ratings. We manufacture some lintels specifically to be used with our cast stone, so they fit perfectly together in construction.
For more information on the specification of lintels why not sign up for our RIBA CPD presentation, and check out the rest of our blog for more helpful tips and advice.