When shopping for the perfect home, a well-built and stable foundation may not be on your radar during the first walk-through, but it definitely should be. After all, what good is a finished basement (your future man cave!) and stylish open-concept kitchen if there’s a threat that the entire structure could collapse? With this in mind, today’s blog post is devoted to the most obvious of foundation defects—visible cracks.
As one of the more costly repairs in a home, foundation damage demands the careful scrutiny of a certified home inspector who understands crack location, pattern, length, and width as they relate to the foundational material used and other factors, such as age of the home and climate. No one likes to find a foundation crack, but not every crack is cause for instant panic. That’s why hiring an experienced and licensed inspector is so important before you place a bid on a home or move in and find big trouble that could have been detected early in the process.
Here is a brief checklist of some of the foundation cracks the inspectors at A-Pro Home Inspection have found after observing many thousands of properties over the last 27 years:
Diagonal Cracks: When your inspector observes these types of cracks in brick, block, or poured concrete foundation walls (they are hard to miss), it is often a sign of vertical movement of the structure or something known as differential settlement—what occurs when the house settles unevenly. Your inspector will look for other evidence in the home to corroborate these suspicions, including drywall cracks that appear above doors and below/above windows, stuck interior doors, windows that don’t open or close smoothly, and sloping floors.
In foundation walls made from concrete masonry units, these cracks will look like “stair steps” (with the cracking either following the mortar joints or worse, extending through the blocks). These cracks frequently manifest themselves in corners. In colder parts of the country, these stair-step cracks may be the result of the frozen ground actually lifting the foundation. This type of crack may also occur in locations that are known for having expansive clay soils. Another possible cause is shrinkage of the foundation material due to moisture or temperature swings.
With poured concrete foundations, cracks appear diagonally but will not be stair-stepped—most likely the result of differential settling which causes the crack to often be wider at one end. This settling may be the result of something as simple as having the gutter system’s downspouts draining toward a particular corner or area of the foundation.
Hairline Cracks: These types of ultra-thin diagonal cracks—frequently found near windows, doors, and corners—are considered a cosmetic issues and don’t pose a threat to the building’s structural integrity. As with any crack, your inspector may caution you to keep an eye out to make sure they don’t grow into a more significant problem. They are most common with new construction foundations and are caused by typical settling and/or minor material shrinkage within the first year of installation.
Vertical Cracks: Your inspector will report on vertical cracks running the length of a poured concrete wall, often the result of foundation settling and natural material curing. Unlike horizontal cracks (below), these types do not present a grave danger of catastrophic foundation failure, but they may allow water to seep into the basement. Recommended repairs include filling with a sealing material to prevent leakage and possible radon gas intrusion.
Horizontal Cracks: Like the stair-step type, horizontal cracks sit at the top of the list of foundation defects you don’t want to come across. Found in both block (more commonly) and poured foundations, horizontal cracks and bowed walls can result from several factors, such as frost pressure in colder climates, vehicle traffic or nearby heavy-machinery at work, poorly installed backfill, or earth-loading. The location of the crack (top third versus middle or lower wall) will provide your inspector with clues as to what forces are causing the damage. For example, a horizontal crack in the upper portion of a wall is a likely indication of frost-related pressure exerted on the foundation. While masonry walls are designed to effectively handle weight from above, their ability to withstand lateral force leaves much to be desired.
The most troubling problem comes when a horizontal crack lessens the foundation’s overall structural integrity, putting the entire building in jeopardy. Bottom line: When your home inspector includes significant horizontal wall cracks in the home inspection report, it is a matter to be taken seriously. Repairing multiple cracks/ bulging walls can be expensive. Not as big of a concern is the appearance of a horizontal crack where the wall meets the basement floor. This commonly occurs due to normal house settling and should be sealed to prevent moisture, radon, and odor penetration.