Cracks in brick masonry are common, especially around windows and doors. Openings in the wall are weak points and are particularly susceptible to cracks. A few hairline cracks in mortar are almost guaranteed with brick veneer and are generally of no concern.
The following lists several causes of cracking in masonry, particularly brick veneer, around windows and doors. It’s possible to have multiple or overlapping causes.
Lintel Expansion
A lintel is a metal support beam placed over windows and doors and serves to support masonry above the opening. Cracks at the opening corners are often caused by expansion as the lintel rusts. Steel expands up to ten times its original size when it corrodes (rusts), which creates stress fractures in surrounding masonry. There is no long-term fix other than eventual replacement of the lintel. Sometimes painting exposed areas of the lintel will slow down rusting.
Most materials expand with temperature. Metal lintels will expand at a higher rate than masonry and cracks can develop from these dissimilar expansion rates.
Lintel Sag
Masonry cracks directly above the window or door opening are often caused by a sagged or failed lintel. Lintels are often greatly undersized or over-spanned, especially over wide garage doors. In some instances, they are holding up a ton or more of brick. Some of these instances stabilize and don’t get worse. In more severe cases the lintel will continue to sag and will need replacement or reinforcement. Replacement is typically costly and invasive. However, a new product is available that reduces the cost of lintel repair: https://www.lintellift.com/
Masonry Expansion/Contraction
Cracks at door and window openings and corners can also be caused by the expansion and contraction of brick. Brick expands with temperature and moisture content and will fracture at weak points in the wall, particularly around openings and changes in direction or angle such as corners. Thermal expansion cracking is prevented through the use of expansion joints placed in brick, a detail nearly always omitted in residential construction. Clay bricks accumulate moisture over time and expand in size. Moisture-related expansion occurs mostly in the first few years and gradually tapers off. Cracks from expansion and contraction tend to be uniform in thickness.
Foundation Issues
Cracks in masonry walls can also be caused by foundation movement, particularly differential settlement. These cracks tend to be asymmetric in width and form a diagonal or stair-step pattern. Typically, a foundation problem severe enough to require repair will result in cracks in interior drywall behind the cracked masonry, as well as sticking or racked doors and windows. Brick is unforgiving of even the smallest movement in the foundation below it, while the wood framing of the home can tolerate much larger movement without a problem. All foundations will settle a small amount, and will typically stabilize. It’s not uncommon to get a few minor or hairline cracks in brick veneer during the initial “settling period”. It’s common to see some foundation-related cracks in the exterior masonry of older (20+ years) homes. However, new foundation-related cracks that suddenly develop in older homes may indicate a change in soil conditions from drought or drainage/gutter issues; these should be investigated promptly.
Note: a home inspection is a snapshot of time. We do not know the history of these cracks, especially in older homes, and cannot tell whether the underlying cause is old and stable, ongoing, or new. A structural engineer should be consulted in the following situations:
1. Cracks greater than hairline width with cracks in drywall inside, opposite the exterior cracks.
2. Exceptionally-severe cracks (>9/16″ in width).
3. Cracks that suddenly develop in older, well-established homes.
Other Causes
There are a myriad of other causes of cracked masonry, including structural issues, shrinkage of wooden framing materials, and seismic (earthquake) events. And, again, there could be multiple or overlapping causes. Diagnosis of the source of cracking is best performed by a structural engineer.
(c) 2023 Todd Thuss