Window Lintels: A Detailed Guide

Window lintels come in many forms depending upon the work they have to do and what the make-up is of the wall in which it sits. A window lintel on the ground floor of a building may actually have to support less than a window lintel that is set below a roof structure.

So how do we know whether a lintel is right for the window opening? What happens if a window lintel fails? Do you have to spend a fortune to make sure you never have a problem?

The good news is that window lintel technology means that picking the right product is not difficult and won’t break the bank.

Here’s our guide to help you through the maze.

What is a Window Lintel?

A window lintel is a structural element that takes the weight of the masonry above the window opening and transfers the load through the structure. The wider the window opening, the stronger the lintel will have to be.

Lintels carry the weight so the window doesn’t have to. While some steel-framed windows are made with built-in lintels, most windows need a lintel to protect them from downward pressure from overhead loading.

A window without a lintel may become bowed under pressure and be difficult to open and close. Without a lintel, the masonry over an opening may become unstable.

What is a Window Lintel Made Of?

Modern window lintels are made from either steel or concrete. They can be installed as single-leaf items for either the inner or outer masonry wall, or as a cavity lintel, either made from a single, folded piece of steel or other combination.

Timber frame buildings also use specifically designed window lintels to carry masonry loads over window openings. These are usually also fixed to the inner timber frame for added stability.

In older buildings, timber or stone lintels bridge the gap over doors and windows. Both can still be used as lintels in certain situations, but in most modern construction the work is done by steel or concrete.

Concrete Lintels

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Steel Lintels

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The Triangulation of Lintel Loads

It sounds complicated, and maybe even a little bit technical, but it really isn’t. Imagine a triangle above the window opening, each side as long as the window is wide. This is the basic way to visualise how much weight a lintel needs to carry.

A small window in a downstairs cloakroom will be narrow so may only need to support a handful of bricks. If it is less than 600 mm wide, it may not need a lintel at all as the loading will be very minimal.

By contrast, a wide bedroom window on the first floor may have to support a ceiling plate that will carry joists and perhaps even rafters.

How Do I Know My Window Has a Lintel?

In a lot of cases spotting whether a window has a lintel is quite simple. Outside the building, look up at the top of the window frame. If the building is built with brick, you might be able to spot a steel strip, which will be the edge of a lintel.

A concrete or stone lintel may be more obvious, especially if it is of a contrasting material. However, on a rendered building, any lintel may be concealed.

Most windows will have a lintel unless they have a self-supporting arch, which is only likely if your building was constructed a significant number of years ago.

What if my Lintel is Broken?

There are a number of tell-tale signs that you have an issue with a window lintel.

• Window operation has become difficult, or stiff, or the mechanism is jammed.
• The window glass has cracked for no obvious reason.
• There is damp, or water ingress, perhaps resulting in mould on the reveals.
• Cracks have appeared above the window in the external masonry.
• There are rust spots on the exterior windowsill.

If a window lintel has failed, either due to manufacturing issues, poor construction specification or methods, or it has simply come to the end of its working life, it may be time to get it replaced.

How Much Does It Cost to Replace a Window Lintel?

If you think back to that triangle test for the amount of masonry a window lintel needs to support, that will give you a clue as to how difficult a job, replacing the lintel, is going to be.

The bigger the lintel, the trickier it will be. The masonry above the lintel, if it hasn’t failed completely, will require temporary support.

Most lintel replacement works will require a scaffold access, acro-propping, and protection to the existing window. Internal finishes may also require protection if the inner leaf needs replacing in the case of cavity lintels.

How Long Does It Take to Replace a Lintel?

For a professional team, replacing a lintel once the access and propping is all set up doesn’t take very long. Most projects can probably be taken from potential disaster to done and dusted in a day or two.

The key metric is to understand how much will have to be rebuilt following removal of the broken window lintel. Fresh mortar takes at least 24 hours to cure to a point where temporary propping can be removed.

It is always a good idea to get more than one quote from a recommended builder before deciding to go ahead with any work.

How High Does a Window Lintel Have to Be?

The usual position for a window lintel is at the head of the structural opening. It is standard practice for an opening to be constructed that allows for a 10mm tolerance between the window being fitted and the opening.

For wider openings, the lintel is often set on padstones, bricks, or concrete blocks that have a higher crush density than regular bricks or blocks. These are designed to take and spread concentrated loads.

In all cases, the window lintel should be positioned directly above the opening.

When a Window Lintel is Fitted Lower.

Some windows are fitted in ‘check’. When this happens the lintel to the outer leaf will be fitted slightly lower than the lintel in the inner leaf.

The window is secured with straps to the inner leaf, but it rests up against the back of the outer leaf, in check. It is a traditional way of fitting windows that is often specified on heritage builds, in arched window designs, or on sites that seek to emulate period designs.

The lintels must be fitted to precise specified measurements to maintain conformity of height levels for the windows in the brick coursing.

Does an Arched Window Need a Lintel?

An arched window does not usually require a lintel, however, there may be a need for a padstone at the springing point of the arch where the pressure from the load directly above the window is transferred.

Similarly, ox-eye round windows also do not require a lintel, as a circular opening will be self-supporting once the mortar has cured.

Does a Bay Window Need a Lintel?

Bay windows do not usually have a lintel fitted directly over the head of the window. The lintel installation for a bay window will be in line with the wall in which the window is set.

The opening for a bay window will be in line with the front wall of the house, so that is where the loading will have to be carried. In a two-storey bay window, which is seen in thousands of homes across Britain, there will be two lintels.

One window lintel will be required to carry the first-floor joists or trimmers, while another will be required to support the roof structure.

Whether rendered or bricked up, the space above the ground floor window will be supported in part by the wide pillared bay window frame, and a cantilever action within the floor structure.

Further Information

Lintels are essential for most windows and come in a wide variety of specifications, so there is plenty of choice when it comes to selecting the right lintel for your job. Whether you are building new, renovating or repairing a window, at Wade, we have the range to suit all circumstances.