Key takeaways
- A lintel carries the masonry above an opening across the gap, so its size, its bearing and its protection must all match the design.
- Bearing is the most often overlooked part of a lintel installation, and it must be measured on sound masonry rather than estimated by eye.
- The cavity tray must be integrated with the lintel and kept clear of blockages, or water will run into the wall behind the window.
- Cracking above an opening usually traces back to differential movement, deflection or corrosion, and each cause has a prevention that belongs in the design and the build.
- Unusual or heavy openings remain the engineer’s responsibility, and any change made on site must go back to the engineer before it is built.
Every window and door in a brick wall sits under a lintel, and most of the time nobody thinks about it until the brickwork above the opening starts to crack or the steel angle begins to rust and stain the face. The lintel is a small component with a large job. It carries the masonry above the opening across the gap and transfers that load onto the solid wall at either side. When it is right, the wall looks as if the opening was always there. When it is wrong, the defect appears as a line of cracking that runs diagonally up from the corner of the window, and the call comes to the builder.
This article covers the choice of lintel for openings in brick veneer and masonry walls, the bearing each lintel needs, how the cavity tray is integrated above the opening, and how to prevent the cracking that usually follows a poor choice. It does not cover the general movement and tie system of brickwork, which is a separate subject, and it does not cover the mortar and joint choices that affect appearance. The focus is the lintel above the opening and the things that have to go right around it.
What the lintel is doing and why the wall above it matters
Brickwork is good in compression and poor in tension, which is why a wall can carry a great deal of weight vertically but cracks when it is asked to bridge a gap. Over an opening the masonry above cannot simply sit on air. In a solid or fully bonded wall, the brickwork above the opening tends to form an arch, and the load from a triangular zone of masonry above the opening is carried into the solid wall on either side. The lintel is the element that carries the load across the gap until the arch is established.
In brick veneer construction the picture is slightly different. The veneer is a non-structural skin fixed to a timber or steel frame, so the structural load above the window is carried by the frame’s own header, and the brick lintel carries only the veneer. That distinction matters because a builder who selects a veneer lintel as if it were carrying the structural load can end up with the wrong element in the wrong place. The frame header is designed by the structural engineer, and the veneer lintel is sized for the masonry it supports.
Choosing the lintel type
The common options are steel angle lintels, precast concrete lintels, reinforced masonry lintels formed with lintel blocks, and, in some framed or specialised situations, timber or engineered lintels. Each has a place. Steel angles are quick to fit and suit many brick veneer openings where the span and the load are modest. They must be galvanised or coated to the exposure of the site, because a steel angle that rusts expands and cracks the masonry around it. Precast concrete lintels suit wider spans and heavier loads, and they are placed with the bearing and the reinforcement as the manufacturer specifies.
Reinforced masonry lintels are formed in the wall itself, with steel bars placed in the mortar of a course of lintel blocks and filled. They suit openings where the wall must be continuous and where a precast element would be awkward to place. They take longer to build and need inspection before the grout is placed, which is a reason to build them with the site supervisor watching rather than leaving them to the end of the day. The comparison below sets out the usual choice.
Where each lintel type usually fits
| Lintel type | Where it usually fits |
|---|---|
| Galvanised or coated steel angle | Modest spans and loads in brick veneer, with the coating matched to the exposure |
| Precast concrete lintel | Wider spans and heavier loads, placed with the bearing and reinforcement the manufacturer specifies |
| Reinforced masonry lintel | Continuous walls where a precast element would be awkward, inspected before the grout is placed |
| Frame header | Structural loads over openings in a timber or steel frame, designed by the engineer rather than picked from a catalogue |
| Engineered or specialised lintel | Unusual spans, heavy loads or unusual openings, where the engineer’s details govern |
The choice is driven by three things: the span across the opening, the load carried above it, and the exposure of the lintel to moisture and corrosion. The lintel must be selected against the engineer’s details or the manufacturer’s load tables for the case, not from memory. Mortar strength and the joint profile above the opening also matter, and are covered in the guide to mortar selection and joint profiles. Where the opening is unusual, the wall is taller than normal, or a floor or roof sits on the masonry above, the design is the engineer’s job, and the builder’s job is to build exactly what the design calls for.
Bearing: the part of the lintel that most often fails
Bearing is the length of lintel that sits on the solid wall at each end of the opening. It is the connection between the lintel and the structure, and it is the first thing to check on site. A lintel that is correct in size but short of bearing cannot transfer the load into the wall, and it will bend, crack the masonry at its ends or drop. The mechanism is simple. The load has to be carried into the wall at a point, and the wall can only accept that load over a sound length of masonry.
The bearing length must be what the lintel design requires, and it must be measured on site, not estimated by eye. The bearing has to sit on solid, sound masonry, which means it cannot be placed over a cut-out, over a cracked or loose brick, or over a head joint that has not been filled. Where the opening is near a corner or a control joint, the usable bearing is shorter than the drawing suggests, and the lintel may have to be moved or the design revised. A lintel that finishes short on one side is a defect, whatever the appearance from the outside.
Check the bearing before the masonry above is laid and again after the lintel is in place. Mark the bearing length on the wall, confirm the lintel type and the direction it is placed, and make sure the lintel is level and sits fully on the bearing. A lintel that is installed on packers or with an unfilled gap at the bearing has not been installed properly, even if it looks secure. Photograph the bearing at each end before it is covered, and record the lintel reference against the opening in the job file.
Cavity trays and getting water out above the opening
A lintel above a window or door sits in the path of water running down the outside of the wall. The cavity tray is the flashing that catches that water and directs it out of the cavity and back onto the face of the wall, above the opening. Without a correctly installed tray, water tracks down the cavity, collects on the lintel and runs into the wall behind the window, where it stains the masonry, corrodes the steel and, over time, weakens the bond around the lintel.
The tray has to be integrated with the lintel, not added after it. It is placed on the lintel or on a suitable support, lapped and sealed at the joints, and turned up at each end so that it does not drain into the wall. Weep holes or the drainage outlets at the base of the cavity must be kept clear, because a tray that directs water to an outlet that is blocked by mortar droppings does not drain at all. The end dams at the ends of the tray should be placed so that water is not trapped at the edges of the opening.
A tray installed at the wrong level or with the lintel bedded over it can look correct from the outside and fail on the inside. Check that the tray is above the opening’s head flashing, that it runs across the full width of the opening plus the ends, and that the mortar has not bridged the cavity above it. The tray is not a decorative element, and the time to check it is before the masonry is closed in, not after the first wet season.
Preventing cracks above openings
Cracking above an opening usually has a cause that can be traced back to the design, the bearing, the lintel or the movement the wall is allowed to make. The most common cause is differential movement: the lintel, the masonry above it and the masonry beside it move by different amounts as the building settles, as the temperature changes or as moisture is absorbed and released. Where the movement is not accommodated, the stress concentrates at the corners of the opening, and the crack runs diagonally from there.
Lintels can also deflect under load if they are undersized or if the masonry above is heavier than the design assumed. A small deflection may be harmless, but a lintel that bends visibly is carrying more than it should, and the brickwork above it will crack as it is forced to follow the bend. The prevention is to match the lintel to the design, check the bearing and avoid loading the masonry above with anything the design did not allow for, such as a stack of materials or a slab that was not expected.
Corrosion is the third common cause. A steel lintel that is not galvanised or coated correctly rusts from the inside out. The rust occupies more space than the steel it replaces, and it pushes the masonry outward, producing cracks and staining on the face. The fix is to specify the coating for the exposure and to keep moisture away from the lintel with a correctly installed tray. Joint placement is the fourth consideration. Control joints placed near an opening relieve some of the movement, and the position should be set in the design rather than added after the cracking has started.
Specifying and checking the lintel on site
The sequence below is the practical version of the principles above. Each step is a check that should be completed and recorded before the next one starts. Most lintel defects are not caused by a single error on the day. They come from a missed check that was never recorded, so the sequence is written to make the checks visible.
Checks before the masonry above is laid
- 1Confirm the designCheck the engineer’s details or the supplier’s load information against the actual opening before anything is ordered.
- 2Check the lintelConfirm the type, the coating and the direction of placement against the drawings.
- 3Mark and check the bearingMeasure the bearing at each end on sound masonry, clear of joints and cut-outs.
- 4Fix the trayInstall the cavity tray across the full opening, lapped, sealed, turned up at the ends and clear of the weep holes.
- 5Record before closingPhotograph the bearing and the tray, and log the lintel reference in the job file before the masonry above is laid.
Where the engineer comes in
Some openings are straightforward and sit within the standard arrangements for the wall and the loads. Others are not. A wide opening, a tall wall above the opening, a floor or roof bearing on the masonry, an opening close to a corner or a change in the wall thickness, and any situation the drawings do not cover all require a design by a suitably qualified engineer. The builder should not decide that an opening is straightforward because it looks familiar.
The structural provisions of the National Construction Code and the masonry design standard set out the requirements for lintels and the walls that carry them, and the certifier will expect the design to reflect those requirements. The details of the Code are not restated here, because the wording and the limits belong in the Code itself. Check the current edition and the requirements that apply to your job before the lintel is ordered, and make sure the design the certifier reviewed is the one that is built.
Worked example: a new window in an existing brick veneer wall
A builder in western Sydney is enlarging a window in the living room of a brick veneer house to bring in more light. The frame above the window carries the roof of a single-storey section, and the existing veneer lintel is a steel angle that is visibly rusting at one end. The owners want the new window wider and the stains removed.
The builder begins with the engineer’s details for the new opening, which specify a frame header in the timber stud wall above and a steel angle lintel for the veneer, galvanised to the exposure of the site. The old lintel is removed carefully, the masonry around it is inspected, and the rusted section is found to have pushed out the brick at the corner. The damaged bricks are replaced, not patched.
The new lintel is set with the bearing measured at each end and marked on the wall. The bearing sits on sound masonry, and the builder notes that one end is closer to a control joint than the drawing suggested, so the bearing is confirmed before the lintel is fixed. The cavity tray is installed over the lintel, lapped, sealed and turned up at the ends, and the weep holes below the window are checked for clearance. Photographs of the bearing, the tray and the lintel reference are taken before the masonry above is laid.
The job file records the lintel type, the coating, the bearing, the tray and the engineer’s reference. When the owner asks about a faint line of mortar in the corner after the first winter, the builder can show what was installed and where. The line is cosmetic, and the photographs confirm the structure was built to the design, which is the difference between a conversation and a claim.
Records and the defect question
Cracking above an opening is one of the most common defect complaints a residential builder receives, and the first question is always what was installed. The Home Building Act sets out statutory warranties that apply to residential building work, including an obligation to carry out the work with appropriate skill and in accordance with the plans and specifications, and the period for claims is set out in the Act. A record of the lintel, the bearing and the tray is the evidence that the work met those obligations, and it is the document that answers the question quickly.
The records need to be made when the work is done, not reconstructed afterwards. A photograph taken before the masonry is closed is worth more than any description written later, and the record should name the engineer’s reference and the lintel product so that the question can be answered from the file. The discipline of keeping these records sits alongside the wider business practice covered in the guide to brickwork movement, joints and ties, and the lintel is one part of the same wall.
The costliest mistake. Setting a lintel short of bearing, or leaving out the cavity tray because the masonry was already going up. The defect shows as cracking and staining years later, and the claim turns on whether the bearing and the tray were ever checked, which is rarely answerable from memory.
For a structured view of how the licensed side of masonry and structural work fits with CPD obligations, the guide to how NSW builder CPD works is the place to start. Where a lintel detail is in doubt, the answer belongs with the engineer, not with the bricklayer’s best guess.
Questions builders ask
What lintel do I use over a window in brick veneer?
The lintel is chosen against the engineer’s details or the supplier’s load information for the actual opening, not from habit. In brick veneer the veneer lintel supports only the masonry, and the structural load is carried by the frame header. Galvanised or coated steel angles are common for modest openings, provided the coating suits the exposure.
Why does the bearing matter so much?
The bearing is where the lintel passes its load into the solid wall, and a short bearing cannot transfer that load properly. Cracking, bending and a drop at the ends are the usual results. Measure the bearing on sound masonry before the masonry above is laid.
Is a cavity tray needed above every lintel?
In most brick veneer walls a cavity tray is part of the detail above a window or door, because water can run down the cavity onto the lintel. The tray must be integrated, lapped and sealed, and kept clear. Confirm the detail against the design and the requirements that apply to the wall.
What causes cracks above a window?
The usual causes are differential movement between the lintel and the masonry, deflection of an undersized lintel, and corrosion of an unprotected steel angle. Each has a prevention that belongs in the design, the lintel selection and the build. A crack alone does not show which cause is at work, so the record of what was installed matters.
When do I need an engineer for a lintel?
Whenever the opening is wide, the wall above is tall, a floor or roof bears on the masonry, the opening sits near a corner, or the drawings do not cover the case. Do not decide that an opening is straightforward because it looks familiar. The engineer’s details govern the lintel, and any change on site goes back to them.
Can I substitute a lintel that is out of stock?
Not without a check. A substitution can change the bearing, the load path or the corrosion protection even when it looks equivalent. Send the change back to the engineer before it is built, and record the decision in the job file.
Sources
- Continuing professional development for builders and swimming pool builders · NSW Government
- General building work licensing · NSW Government
- Home Building Act 1989 (NSW) · NSW Legislation
Published 26 October 2026. General information for builders, not legal, financial or engineering advice for a specific job. Check current requirements with the relevant regulator or standard before relying on them.
