Brick foundations, also known as unreinforced masonry (URM) foundations, were commonly used in residential construction until the early 1930s. While brick was a popular and readily available material, these foundations lack the structural reinforcement necessary to withstand seismic events effectively. This has led to significant concerns in areas with earthquake activity, where unreinforced masonry is particularly vulnerable to shaking and movement. Here’s a look at the history, risks, and considerations for homeowners with brick foundations, along with recommendations for managing seismic risks.

Until the early 20th century, brick was a primary material for foundations, especially in regions where it was easily sourced. Builders relied on unreinforced masonry because it was durable, fire-resistant, and relatively cost-effective. However, as knowledge of earthquake engineering advanced, it became clear that unreinforced brick was inadequate for areas prone to seismic activity. In the 1930s, building codes began to prohibit the use of brick foundations for residential structures, especially in earthquake-prone regions, due to their inability to withstand ground shaking.

Since then, most new construction has shifted to reinforced concrete or other materials that perform better under seismic stress. However, many older homes built before these regulations remain with their original brick foundations, making them more susceptible to damage during an earthquake.

Brick foundations are unreinforced, meaning they lack the internal steel bars (rebar) or other reinforcements used in modern foundations to absorb seismic forces. Without reinforcement, brick foundations are brittle and susceptible to cracking or even collapsing when exposed to the lateral forces generated by an earthquake.

During a seismic event, the shaking can cause unreinforced brick to break apart or lose cohesion. This lack of flexibility means that rather than bending and flexing, the bricks are likely to crack and displace, potentially resulting in severe structural instability. For homeowners in earthquake-prone areas, this vulnerability can present a significant safety risk.

Many homes with brick foundations have survived past earthquakes, which might give a false sense of security. While it’s true that these foundations may have withstood historical events, their continued resilience cannot be guaranteed. Each seismic event affects structures differently, and an unreinforced masonry foundation that has survived previous quakes may still be at risk in future ones.

For prospective buyers, it’s important to note that homes built with brick foundations generally have not been retrofitted and thus retain this inherent vulnerability. If you are considering purchasing a home with a brick foundation that has not been replaced or upgraded, it’s wise to evaluate your tolerance for seismic risk.

Replacing a brick foundation with a modern, reinforced concrete foundation is the most effective way to improve seismic resilience. However, foundation replacement is a major undertaking, both in terms of time and cost. Budgetary costs can start around $1,000 per linear foot, which can quickly add up, especially if the soils report recommends additional support measures. Although costly, foundation replacement provides long-term structural stability and is the most reliable way to protect against seismic risks.

For those looking for a less invasive and costly solution, seismic retrofitting can improve the stability of a brick foundation. Retrofitting involves adding elements like steel braces, anchor bolts, or reinforcing materials to improve the foundation’s connection to the rest of the structure. While retrofitting won’t make a brick foundation as resilient as a new concrete foundation, it can significantly reduce the risk of failure in a moderate seismic event. Retrofitting costs vary but are generally lower than full replacement, making this a more budget-friendly option for homeowners seeking some level of protection.

Given the high cost of replacement, homeowners should weigh their risk tolerance and awareness of seismic risks when deciding whether to take action. In some cases, especially for those in less active seismic regions, monitoring the foundation for any changes or issues may be sufficient. Regular inspections can help identify cracks or other signs of deterioration, allowing you to address potential problems early.

If you own or are considering purchasing an older home with a brick foundation, it’s essential to understand both the risks and potential costs involved. While replacing the foundation offers the most security, it is a significant investment that may not be feasible for every homeowner. Seismic retrofitting provides an intermediate solution, though it may not fully protect the structure in a large earthquake.

Ultimately, the best course of action depends on your specific circumstances, including the home’s location, local seismic activity, and your risk tolerance. For many older homes with unreinforced masonry foundations, conditions similar to those described are common, so awareness is the key to making an informed decision.

Brick foundations are a beautiful but outdated construction feature that lacks the resilience needed to withstand modern seismic forces. While many older homes have managed to survive past events, future earthquakes may not spare these unreinforced structures. For homeowners, understanding the potential risks and evaluating options for retrofitting or replacement can help you make the best decision for your safety, investment, and peace of mind. In the end, an informed approach will help you protect your home and its occupants against the unpredictable forces of nature.