MET SURVEYORS

Why Do Cracks Form Around Doors and Windows?

 

Cracking can form around openings for several reasons.

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Common causes include:

• Normal settlement

• Drying shrinkage

• Thermal movement

• Lintel movement

• Poor masonry bonding

• Previous alterations

• Movement between different materials

• Differential movement

• Ground movement

• Subsidence

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Because the wall is weaker around an opening, movement elsewhere in the structure can become concentrated at the corners.

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Are Cracks Around Windows Always Structural?

 

No.

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Fine cracks in plaster around a window may be cosmetic.

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They can be caused by:

• Drying plaster

• Decoration

• Changes in temperature

• Minor shrinkage

• Movement at plasterboard joints

• Slight movement between the frame and surrounding finishes

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These types of cracks are common and may not indicate a structural problem.

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More attention may be required where cracks extend into masonry, are visible externally or are becoming wider.

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Diagonal Cracks Around Windows

 

Diagonal cracks extending from the corners of windows are one of the most common patterns associated with structural movement.

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They may appear:

• Above the window

• Below the window

• From one corner only

• From several corners

• Internally and externally

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Possible causes include:

• Settlement

• Lintel movement

• Differential movement

• Foundation movement

• Subsidence

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A diagonal crack does not prove subsidence, but it can justify further investigation where other signs of movement are also present.

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Cracks Above Doors

 

Cracking above a door can result from several causes.

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One possibility is movement around the lintel.

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Lintels support the masonry above openings. If the lintel is inadequate, deteriorated or has moved, cracking can develop above the opening.

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Other possible causes include:

• Settlement

• Poor bonding

• Thermal movement

• Structural alterations

• Ground movement

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The pattern of the crack and condition of the surrounding wall need to be considered.

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What Is Lintel Movement?

 

Lintels are structural elements installed above doors and windows to support the wall above.

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Older properties may contain:

• Timber lintels

• Steel lintels

• Concrete lintels

• Brick arches

• Stone lintels

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Problems can occur where a lintel has:

• Corroded

• Rotated

• Deflected

• Deteriorated

• Been inadequately supported

• Been altered during replacement window works

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Lintel movement can create cracking that may initially look similar to subsidence.

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Cracks After Replacement Windows

 

Cracking can sometimes appear after windows have been replaced.

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This can happen where:

• The original frame contributed to supporting masonry

• A suitable lintel was not installed

• Existing structural support was disturbed

• The new frame was fitted too tightly

• Surrounding finishes were disturbed

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This is particularly relevant in older properties where previous window frames may have been replaced without fully understanding the original construction.

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If cracks develop after replacement windows have been installed, the supporting structure above the opening may need to be considered.

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Cracks Wider at One End

 

A tapered crack can be more significant than a fine uniform crack.

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Where the crack is wider at one end, this may indicate that one part of the wall has moved relative to another.

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Possible causes include:

• Differential settlement

• Lintel movement

• Foundation movement

• Subsidence

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The crack should be considered alongside any nearby distortion, sticking windows or movement elsewhere in the property.

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Cracks Visible Inside and Outside

 

Cracking visible on both sides of the same wall can be more significant than a crack limited to plaster.

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If a crack appears internally and externally in a similar location, this may indicate movement through the wall construction rather than simply in the decorative finish.

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This does not necessarily mean the problem is serious, but it usually warrants closer consideration.

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Sticking Doors and Windows

 

Doors and windows becoming difficult to open or close can sometimes be associated with movement.

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Possible signs include:

• Doors catching against frames

• Windows no longer closing properly

• Gaps appearing around frames

• Distortion to openings

• Locks no longer aligning correctly

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However, timber frames can also swell or shrink with changes in moisture and temperature.

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Sticking alone does not prove structural movement.

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It becomes more significant where cracking is also present.

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Cracks Around Bay Windows

 

Bay windows are another common location for cracking.

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Bay structures may have:

• Different foundations

• Different wall construction

• Separate roof structures

• Historic alterations

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Movement may occur where the bay joins the main building.

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Possible causes include:

• Settlement

• Inadequate support

• Deteriorated construction

• Differential movement

• Ground movement

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Cracking around a bay should be assessed carefully where it appears to be increasing or where the bay itself appears distorted.

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Cracks Around Patio and French Doors

 

Large openings can place greater demands on the structure above.

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Where patio doors, French doors or bifold doors have been introduced, cracking may develop if structural support is inadequate.

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Possible causes include:

• Undersized lintels

• Poor bearing at lintel ends

• Inadequate structural design

• Movement following alteration

• Differential settlement

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Where a large opening has been formed as part of an extension or refurbishment, the history of the alteration can be important.

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Cracks Around Doors in Extensions

 

Cracking around openings in extensions is relatively common.

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The extension may have different foundations from the original property and may settle at a different rate.

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Possible causes include:

• Initial settlement

• Movement between old and new construction

• Inadequate foundations

• Poor structural detailing

• Ground movement

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The age of the extension and whether the cracking is still changing are important factors.

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Can Subsidence Cause Cracks Around Doors and Windows?

 

Yes, subsidence can cause cracking around openings.

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Because doors and windows interrupt the wall, structural movement may become visible there first.

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Possible signs may include:

• Diagonal cracks

• Cracks wider at one end

• Cracks visible internally and externally

• Sticking doors or windows

• Distortion to the opening

• Reopened previous repairs

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However, these same signs can result from other forms of movement.

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Subsidence should not be diagnosed simply from one crack.

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When Should You Be Concerned?

 

Professional advice should be considered where:

• Cracks are becoming wider

• Several openings are affected

• Cracks are visible internally and externally

• Doors or windows have started sticking

• Frames appear distorted

• Previous repairs have reopened

• Cracking has appeared suddenly

• Cracks are accompanied by movement elsewhere

• You are concerned about possible subsidence

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When Is a Specific Issue Survey Appropriate?

 

Where there is one clearly defined area of concern, such as cracking around one window or door, a Specific Issue Survey may be appropriate.

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Examples include:

• One diagonal crack above a window

• Cracking around a door frame

• Movement around a bay window

• A suspected lintel problem

• Cracking after replacement windows

• One localised area of structural concern

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Our Specific Issue Survey concentrates on the particular problem and includes a written report with recommendations.