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Door Lintels: A Detailed Guide

Door Lintels: A Detailed Guide

If a door is set in a masonry wall, whether it is brick, block, or stone, there will be a lintel overhead holding up the structure directly above it. In a timber-framed construction, there will be a lintel over any external doorway too, supporting the external masonry leaf.

In older buildings or commercial developments, often the internal partition walls will be built from block or brickwork, which means that lintels will also be required over doorways.

Here’s our guide to door lintels.

What Size Lintel do I Need for a Door?

You can answer that question with another; how wide is the door opening? The bigger the opening, the bigger the lintel, not just in length, but height.

Also, what is the area directly over the door supporting? If there is a second storey, a roof, or a window opening, then it will all have a bearing on the size of the lintel required.

Is steel or concrete better? Steel and concrete lintels can be specified for all doorways. It all comes down to wall finishes, loads and budget.


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Do I Need a Lintel for My Door?

Unless you have invested in steel-framed security doors with built-in lintel support in the frame header, then yes, you will need a lintel to be fitted over the doorway.

Without a lintel, the masonry overhead will eventually compress the top of a timber or aluminium doorframe. Eventually, the performance of the door will be affected as the opening succumbs to the pressure.

If a lintel isn’t present, the masonry above the door opening will eventually fail, which could lead to further structural problems.

Can I Cut a Lintel to Fit?

If required, a concrete lintel can be cut to length on site, as long as the exposed reinforcement is properly protected with mortar. Cutting a concrete lintel won’t otherwise affect its performance as a load-bearing item.

It’s not a good idea to cut a steel lintel to size as it will compromise the integrity of the galvanised, anti-corrosion finish. Doing so will likely also void any applicable warranty.

Top Tip:

You can take 100mm concrete lintel off-cuts and keep them to be recycled as padstones.

Structural Door Openings

Door openings in any load-bearing wall interrupt the continuity of the load-bearing ability of the wall. In order to maintain a uniform level of support, a lintel is used to bridge the aperture.

Structural door openings are always larger than the final finished doorset required to be installed to allow for any minor variation during the doorset’s manufacture or tolerances allowed in the construction of the masonry wall.

Care should always be taken to ensure that a structural opening is set as square and level as possible as any deviation can make the installation and operation of a doorset problematic.

Top Tip:

It is best practice to work out the coursing to the bottom of a lintel from a datum point and not the structural floor level. Any variation in the foundation, or over-site slab, makes a datum a more reliable point from which to start.

Fire Door Tolerances

The tolerances for fire doors are usually tighter than for standard doors to ensure there is no passage for fire around the outside of the frame. Apartment front doors will have an intumescent liner that fits around the frame, next to the masonry.

If a concrete lintel is specified here, it will likely also have to bear a fire rating to ensure compliance with building regulations, for control of smoke as well as fire.

Single Doorway Lintels

If a door is a standard 826mm wide, add the frame width and gap (25mm and 3mm) and you will probably require a minimum structural opening of 892mm (826mm + 56mm).

In this case, it may be simpler to size the opening at 900mm to allow for any build tolerance over the height of the doorway. It’s always a good idea to also allow approximately 10mm tolerance at the door head.

With a minimum bearing of 100mm to each side of the doorway (as the opening is less than 1000mm), a lintel of 1100mm in length will be required (900mm + 100mm + 100mm). Concrete lintels can be cut to size if space on either side of the opening is limited by other factors.

UK Building Regulations

Lintels are all about the distribution of weight and loading forces safely to either side of an opening. Any lintel up to 1.2m in length will need a bearing of 100mm at each end.

If the position of the lintel is in an external wall that requires a cavity tray, the bearing will have to be extended to 150mm at each end.

Some steel cavity lintel profiles, with appropriate corrosion resistance, are designed to do the job of a cavity tray. Check the manufacturer’s recommendations as you could save time and materials.


Using Larger Steel Lintels

The bigger the opening, the bigger the lintel. The wider the opening is, there is more to support above it, so the lintel you need may also get taller.

In a concrete lintel, the steel reinforcement is embedded in the lower section of the beam. Make sure that you install the lintel the right way up. Check for a marking on the lintel to let you know which face is the top.

If the marking is missing, check the ends of the lintel to see if you can spot the ends of the steel tendons.

Bigger Single Doors

The standard door size of 826mm is too narrow for many wheelchair access requirements, even though the minimum clear space required by law is 775mm.

Many Local Authorities recommend a minimum access of 950-1000mm, which will bring a structural opening over the one-metre mark.

The upshot of this is that straight away, the lintel will need to be 300mm wider than the opening to provide the right level of bearing.

Bigger Overhead Loads

The structure directly above the door opening will also inform whether the door lintel will need to be standard, heavy, or extra-heavy duty.

Looking at the equilateral triangle directly above the doorway will tell you just what load the lintel will have to cope with. On the outer leaf, it may simply be some face brickwork, which is not too heavy.

However, it’s likely that the inner leaf will need to support either floor joists or roof rafters and will be dealing with bigger loads.

Top Tip:

When using a steel cavity lintel, build the masonry up to both the inner leaf and outer leaf at the same time otherwise the differential between loads could cause the steel flange to twist.

Double Doorways and Patio Doors

Interconnecting double doors from one room to another, or wider patio doors will obviously require the use of longer lintels.

It’s recommended that anything over three metres has at least a 200 mm bearing at either end of the lintel. This is not too much of a problem when building from the ground up, but it’s a different story if you are renovating, or retrofitting.

Longer lintels will likely require propping while the masonry courses overhead cure. As the mortar dries, the masonry directly above the lintel, up to three courses of brick, actually reinforces the lintel and increases its load-bearing strength.

However, this is a compound benefit and doesn’t mean that a lower-grade lintel than the one specified will do.

Bi-Fold Doors

The trend of turning a garden into an outdoor room, and bringing the backyard into the home, has caught on with a vengeance in the UK. Bi-fold doors that span the width of a back wall are a spectacular addition to any room or extension.

Your best bet would be to use a steel lintel, as these can take on the largest spans, and can be used for openings up to 4.5 metres. Order one that is 4800mm to deliver a 150mm bearing on each end.

Again, these wider spans will require the lintel to be propped until the masonry has been allowed to cure to prevent any sagging or twisting. 

Top Tip:

Any opening above 4.5 metres will take you into hot-rolled steel (RSJ) territory! When considering installing a doorset of this size in an existing building, or extension, it’s always a good idea to seek professional advice.

Can I Use a Timber Lintel?

UK Building Regulations do not permit the use of timber lintels to support masonry or other rigid construction materials. If a timber lintel is used it must be suitably protected from the weather.

Timber lintels, or headers, are used in residential and commercial timber frame construction and are supplied as part of a designed, pre-made modular build system. As such, timber lintels are not generally available to buy.

Internal Door Lintels

Internal walls will sometimes require door lintels in either steel or concrete, dependent upon loadings or finish.

Masonry Walls

Fair-faced blockwork, pointed and painted, is commonly used in commercial construction, and in back-of-house, or communal, functional parts of residential projects.

Concrete lintels are perfect in this situation as they often require no further finishing and are equally good bases for paint or plaster.

For larger masonry openings, steel lintels that can support wet loads straight away are ideal for fast-moving projects.

Non-structural Timber and Steel

If your internal partitions are timber frames or metal studs, then it is unlikely that you will require a door lintel. In timber and metal partition walling that is non-loadbearing, there will be a door ‘header’ instead.

The door header will simply be a length of timber or metal bracing that will secure the top of the door opening between two studs.

In some cases, especially when the ceiling height is higher than standard, there may be a requirement for additional bracing, but it is unlikely that there will be any requirement for lintels.

Door Lintel Prices

Investing in the best lintel you can afford is always best practice.

No one wants a lintel to fail, so it is always worth budgeting for a lintel that covers the specification indicated for the loadbearing required.

Having said that, if the wall above a doorway is fair-faced blockwork, or is due to be rendered, then a standard economy range concrete lintel will usually beat steel on price.

It has to be remembered that in external walls there are two leaves that require support, the inner and the outer. Steel cavity wall lintels do both at once, while you will need two concrete lintels to do the same job.

However, the point is that standard doorways that require a 1200mm lintel won’t necessarily be expensive unless there is a special requirement for extra-heavy-duty performance.

Further Information

For further information or help in specifying or ordering lintels for your project, talk to a member of our team today.

Next article How Much Weight Can a Concrete Lintel Support?

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