Cracks appearing in the brickwork around your windows can be worrying, particularly when they seem to appear suddenly or gradually become more noticeable.
While some cracks are caused by normal movement in building materials, others can indicate a problem with the structural support above the window, including a damaged, deteriorating or failing lintel.
The short answer: Cracks around windows can be caused by temperature changes, settlement, moisture, previous building alterations or lintel failure. Stepped cracks above window corners, sagging brickwork and windows that become difficult to open can indicate a structural problem that needs professional assessment.
Understanding what's causing the cracking is the first step towards deciding whether the brickwork needs a simple repair or more substantial structural work.
What Causes Cracks in Brickwork Around Windows?
Windows create openings in a property's external walls. The surrounding brickwork needs to remain properly supported, particularly above the opening where the weight of the masonry must be transferred to either side.
Cracks can develop for several reasons.
1. A Damaged or Failing Window Lintel
A lintel is a structural support installed above a window or door opening. Its job is to carry the weight of the masonry and other applicable loads above the opening.
Depending on the age and construction of your home, the lintel may be made from steel, concrete, timber or another structural arrangement.
Over time, lintels can deteriorate, corrode or become inadequate for the loads they're supporting.
When a lintel no longer provides sufficient support, the brickwork above the window may begin to move, resulting in cracks around the opening.
Common warning signs include:
Stepped cracks extending from the upper corners of windows
Horizontal cracks along the brickwork above a window
Sagging or uneven brick courses
Gaps developing between the window frame and surrounding masonry
Windows becoming difficult to open or close
These symptoms don't automatically confirm lintel failure, but they should be investigated.
Where a defective lintel is responsible, professional lintel repair or replacement may be required to restore the correct structural support.
2. Natural Settlement and Building Movement
Properties can experience movement over time as building materials settle and the ground beneath the foundations changes.
Small amounts of historic movement don't necessarily indicate an ongoing structural problem.
However, significant or continuing movement can cause cracks to develop around windows and doors because openings create areas where stresses become concentrated.
If cracks are widening, appearing in several locations or accompanied by other signs of movement, further investigation may be needed.
3. Temperature Changes and Expansion
Brickwork, mortar, concrete and steel respond differently to changes in temperature.
As materials expand and contract, small cracks can sometimes develop around windows, particularly where different materials meet.
These cracks may be relatively minor, especially if they remain narrow and stable.
However, the appearance of a crack alone isn't enough to determine its cause. Similar patterns can sometimes result from structural movement or defective support.
4. Corrosion of Steel Lintels
Steel lintels can deteriorate when exposed to moisture, particularly where their protective coating has failed or water is entering the surrounding masonry.
As steel corrodes, the rust can occupy more space than the original metal, placing pressure on the surrounding brickwork.
This expansion can cause mortar joints to open, bricks to move and cracks to develop above the window.
In some cases, the lintel may also lose structural capacity as corrosion progresses.
Simply filling the cracks won't address the underlying problem if the steel continues to deteriorate.
5. Previous Window Replacement
Sometimes cracks appear after old windows have been replaced.
Certain older properties were constructed with window arrangements that provided some support to the masonry above. Replacing those frames without ensuring adequate independent support can expose an existing structural weakness.
Cracking can also occur if the masonry or existing lintel was disturbed during the replacement process.
If cracks have appeared shortly after new windows were installed, it's worth checking whether the brickwork above the opening is properly supported.
What Do Different Cracks Around Windows Mean?
The shape and location of a crack can provide useful clues about its possible cause.
However, the crack pattern alone cannot confirm the underlying problem.
Stepped cracks above window corners: Lintel movement, inadequate support or wider building movement.
Horizontal cracks above a window: Lintel corrosion, expansion or movement in the masonry.
Diagonal cracks extending from window corners: Settlement, foundation movement or localised structural stress.
Fine vertical cracks: Temperature-related movement, shrinkage or other building movement.
Cracks accompanied by sagging brickwork: Possible loss of structural support above the opening.
Particular attention should be paid to cracks that are new, widening or accompanied by visible movement in the brickwork.
Are Stepped Cracks Above Windows a Sign of Lintel Failure?
They can be.
Stepped cracks follow the mortar joints between bricks, creating a staircase-like pattern.
When these cracks appear above the corners of a window, one possible explanation is that the lintel is no longer adequately supporting the masonry above.
This can happen because the lintel is damaged, corroded, incorrectly installed or insufficient for the loads it carries.
However, stepped cracking can also be caused by other forms of structural movement, including foundation settlement.
A professional assessment is needed to establish whether the lintel is responsible and what repair is appropriate.
When Should I Worry About Cracks Around My Windows?
Not every crack is a sign of serious structural damage.
Fine, stable cracks can sometimes be caused by normal movement in building materials.
However, you should arrange an assessment if you notice:
Cracks becoming wider or longer
Stepped or diagonal cracks developing around window openings
Brickwork appearing to sag or bulge
Bricks becoming loose or displaced
Windows or doors suddenly sticking
Cracks appearing on both the inside and outside of the property
New cracking following window replacement or structural alterations
If brickwork appears unstable, is visibly dropping or presents a risk of falling, keep people away from the affected area and seek urgent professional advice.
The sooner the cause is established, the easier it is to determine what work is necessary.
Can a Failing Lintel Cause Cracks Below a Window?
Yes, although cracking below a window doesn't necessarily mean the lintel has failed.
A defective lintel can contribute to movement in the surrounding masonry, but cracks beneath windows can also arise from foundation movement, problems with the sill, thermal movement or other structural defects.
It's important to assess the wider wall rather than assuming every crack near a window has the same cause.
Can You Repair Cracked Brickwork Without Replacing the Lintel?
Sometimes.
If the cracking is minor, stable and unrelated to a structural defect, localised mortar repairs or other appropriate masonry repairs may be sufficient.
However, if the lintel is damaged or failing, repairing the visible cracks alone is unlikely to provide a lasting solution.
The masonry may continue to move if the underlying structural problem remains.
Depending on the condition of the existing support, the appropriate solution may involve:
Repairing or strengthening the existing lintel
Replacing a damaged or inadequate lintel
Installing additional structural support
Rebuilding affected sections of brickwork
Repointing once the underlying cause has been resolved
The correct repair depends on the property's construction and the condition of the lintel and surrounding masonry.
How Are Damaged Window Lintels Repaired or Replaced?
Where an inspection identifies a defective lintel, the repair process will depend on the existing construction and the extent of the damage.
A typical lintel replacement project may involve the following stages.
1. Assessing the Existing Lintel
The first step is identifying the type and condition of the lintel, the loads it supports and whether the surrounding masonry has been affected.
2. Determining the Correct Structural Solution
If the lintel needs replacing, a suitable replacement must be specified for the opening and loads above.
This may involve structural calculations depending on the complexity of the work.
3. Supporting the Brickwork
Where required, temporary support is installed to safely carry the masonry and other loads while the defective lintel is removed.
4. Repairing or Replacing the Lintel
The damaged support is removed or repaired, and the appropriate replacement or strengthening system is installed.
5. Making Good the Brickwork
Once the structural support has been restored, affected masonry can be rebuilt, repointed or otherwise repaired as necessary.
The aim isn't simply to hide the cracks. It's to address the reason they appeared in the first place.
For more information about the process, visit our Lintel Repair & Replacement service page.
How Much Does Window Lintel Replacement Cost?
The cost of repairing or replacing a window lintel depends on several factors, including:
The width of the window opening
The type and condition of the existing lintel
Whether the property has solid or cavity walls
The extent of the damage to the surrounding brickwork
Access requirements, particularly for upper-floor windows
The temporary support and structural work required
Whether additional masonry repairs are necessary
A straightforward lintel replacement may be considerably less involved than a project requiring substantial brickwork reconstruction or more complex structural support.
An assessment of the existing opening is the best way to establish the work required and provide an accurate quotation.
Do I Need Building Regulations Approval to Replace a Window Lintel?
Replacing a structural lintel can involve work subject to Building Regulations in England.
The requirements depend on the nature of the alteration, whether structural support is being changed and the specific circumstances of the property.
Where Building Regulations approval is required, the proposed support must be suitable for the loads it carries and the work must comply with the relevant requirements.
It's important to establish the approval requirements before starting structural repairs.
FAQs About Cracks Around Windows
Why is the brickwork cracking above my window?
Cracks above a window can be caused by a defective lintel, building movement, temperature changes or previous alterations. If the brickwork is sagging or the cracks are widening, the support above the opening should be professionally assessed.
Does a crack above a window mean the lintel has failed?
Not necessarily. Although a damaged or inadequate lintel is one possible cause, similar cracks can result from settlement or thermal movement. An inspection is needed to identify the cause.
Can a rusty lintel cause brickwork to crack?
Yes. When a steel lintel corrodes, expanding rust can exert pressure on the surrounding masonry, causing mortar joints to open and bricks to move. Corrosion can also weaken the lintel itself.
Can new windows cause cracks in brickwork?
Cracking can sometimes appear after window replacement if the existing masonry support was inadequate or disturbed during installation. This is particularly relevant in older properties where the original window arrangement may have contributed to supporting the brickwork.
Will repointing fix cracks above a window?
Repointing may be appropriate for minor, stable mortar defects, but it won't resolve a failing lintel or ongoing structural movement. The underlying cause should be established before cosmetic repairs are carried out.
Can a damaged lintel be repaired instead of replaced?
In some cases, yes. Whether repair or replacement is appropriate depends on the lintel's material, condition, remaining structural capacity and the surrounding brickwork.
Are cracks around windows a sign of subsidence?
They can be, but subsidence is only one possible explanation. Cracking around window openings can also result from defective lintels, temperature-related movement and other localised structural issues.
Concerned About Cracks Around Your Windows?
Cracks in the brickwork around your windows shouldn't automatically be treated as a major structural problem, but they shouldn't be ignored either.
If the cause is a deteriorating or inadequately supported lintel, addressing the problem can help prevent further movement and damage to the surrounding masonry.
Wall Away provides structural alteration services across Hertfordshire, Bedfordshire and North London, including lintel repair and replacement.
If you've noticed stepped cracking, sagging brickwork or signs of movement around your windows, contact Wall Away to discuss an assessment and the appropriate structural repairs.
Find out more about our Lintel Repair & Replacement service or get in touch to discuss your property.