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| Each week, the Silicon Valley Association of Realtors (SILVAR) shares local housing data, sales trends and other real estate-related topics. This week’s column provides information on how to inspect your home’s foundation for damage from Nathan Toothman of BEAR Engineering, who was the guest speaker at a recent association event. |
When it comes to foundation problems, water is by far the biggest menace. That’s why it’s a good idea to inspect your home’s foundation for cracks and other winter storm damage after the end of the rainy season.
Taking a proactive approach can go a long way in helping you avoid expensive repairs, according to Nathan Toothman, chief executive officer and principal engineer of BEAR Engineering, a foundation inspection and engineering company that serves the San Francisco Bay Area.
Check interior walls and exterior stucco for cracks. Large cracks, uneven floors, door and window frames with large gaps or that are difficult to close are signs of a settlement issue, which can be caused by poor drainage around your home.
While the appearance of a newly discovered and unsettling crack in your garage floor or along your home’s exterior can be concerning, such discoveries are frequently less alarming than they appear, Toothman told members of the Silicon Valley Association of Realtors during a recent presentation on how to inspect a foundation for damage.
“Cracks are usually what prompts home inspections,” Toothman said. “Sometimes it’s concerning, but a lot of times it’s not.”
Not all foundation cracks are created equal, he explained. There are many culprits – in addition to water – that can cause foundation damage, including construction methods, seismic movement, materials, a home’s age and location, and soil composition.
Foundation cracks each have their own specific diagnostic approaches and common repair techniques, he explained.
Here’s what to know about various types of foundation cracks:
Horizontal cracks
Horizontal cracks are considered “a high-urgency issue.”
These types of cracks run horizontal across the foundation wall and can indicate significant structural problems that could lead to drywall damage.
The location of a home – and the soil on which it’s built – can determine whether it is more prone to horizontal cracks. Some areas have soils with more movement, which can lead to foundation issues, he explained.
The soil content of much of Santa Clara and San Mateo counties includes clay, which is dense and slow to drain water. It is considered an “expansive soil”: When it gets wet, it expands, and when it dries out, it contracts. This can potentially cause foundation settlement and lead to horizontal issues.
The soil along the bay, for example, is a mix of poorly drained silty clay loam, sandy and gravelly loam and bay mud, all of which contain clay.
In Foster City, East Palo Alto and Redwood Shores, a lot of homes have severe horizontal cracking, Toothman said.
A home’s age and construction methods also can determine whether your home might be more prone to horizontal cracks.
According to Toothman, homes built prior to 1945 didn’t typically use rebar, just concrete, which on its own is very prone to cracking.
When to Worry
Here are some signs that your home may have foundation problems:
- Cracks wider than 1/8 inch
- Horizontal cracks
- Diagonal cracks
- Cracks that are growing/expanding
- Uneven floors, doors and windows that stick
– Information from Groundworks & Bay Area Underpinning
Those built after 1945 typically have rebar. Horizontal cracks in these homes are typically caused by rebar rusting within the foundation. Rusting of the rebar is accelerated by wet or salty soils, water leaks and construction errors, such as placing rebar too close to the ground’s surface.
Minor horizontal foundation cracks can be repaired by chipping, cleaning or replacing rebar and sealing with epoxy and mortar. More complex cracks require removing damaged sections, reinforcing with steel bars and repouring concrete.
Vertical cracks
Vertical cracks, which run straight up and down, are generally less severe than horizontal cracks. They can be caused by several factors, including normal settling, expansive soils combined with shallow foundations, a lack of rebar in foundations built before the mid-1940s, seismic or earthquake activity.
Small vertical cracks are usually repaired with an epoxy injection or can sometimes just be monitored for changes over time.
Medium vertical cracks often require sill plate and epoxy repair.
Large vertical cracks typically need localized underpinning – the installation of new and deeper footings or piers that extend below the existing one – to stabilize and strengthen a building’s foundation
“It all depends on how complex the house is,” Toothman said. “Hillsides can be higher risk but not always. Newer homes tend to be built a little deeper, so the risk is usually greater for older homes.”
Diagonal cracks
Diagonal cracks are common and generally appear at a 45-degree angle from corner to corner on the wall as a result of inadequate soil compaction, fluctuations in soil moisture and insufficient drainage. They can indicate uneven foundation settling or structural problems. A professional should evaluate these types of cracks.
Potential remedies involve foundation repair, soil stabilization methods or structural reinforcement.Toothman recommended that when in doubt, addressing cracks early is essential to avoid significant damage to your foundation and the structural stability of your house. Diagnosing foundation problems often involves a floor level survey, which entails taking precise measurements and analysis to detect subtle variations in floor elevation.
Silicon Valley Association of Realtors (SILVAR) is a professional trade organization representing 5,000 Realtors and affiliate members engaged in the real estate business on the Peninsula and in the South Bay. SILVAR promotes the highest ethical standards of real estate practice, serves as an advocate for homeownership and homeowners, and represents the interests of property owners in Silicon Valley.
The term Realtor is a registered collective membership mark which identifies a real estate professional who is a member of the National Association of Realtors and who subscribes to its strict Code of Ethics.
Real Estate Editor Linda Taaffe contributed to this article.
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