Most multiplexes (fourplexes, 6-plexes, SSMUH, etc.) share the same construction methods as standard houses, leaving them just as vulnerable to destruction when a wildfire sweeps into the neighbourhood, as we see with the wildfires around Los Angeles now.
Designing wildfire-resistant small-scale multi-unit housing (SSMUH) is essential to protect homes and communities as climate change leads to more intense and destructive wildfires. This article outlines the most effective fire-hardening strategies to incorporate into SSMUH design. You will gain practical knowledge on how to safeguard your property and investment while ensuring a safer environment for residents.
The frequency and severity of wildfires are escalating. Even communities once thought - reasonably or not - to be safe are now facing devastating losses, as seen in L.A. (Palisades, Eaton, Sunset, Hurst, Lidia, and Woodley wildfires) and Maui last year. Traditional construction methods leave homes in wildland urban interface (WUI) areas dangerously exposed to fire. Without adopting wildfire-resistant designs, SSMUH buildings risk total destruction, threatening the lives and homes of multiple families.
The potential impact of wildfires on SSMUH properties is catastrophic. A single blaze can render dozens of families homeless, disrupt entire communities, and cause emotional and financial devastation greater than that in a single-family neighbourhood. For developers and homeowners alike, fire resilience is not just an option—it’s a necessity even before considering insurance underwriters quietly cutting fire coverage. Implementing fire-resistant design ensures a safer future for residents and protects valuable investments.
The Impact of Strong Winds on Fire Spread in Urban Areas
Although largely unpredictable, the behavior of wildfire is significantly influenced by wind, which serves as both a driver of fire spread and an enabler of ember distribution. Gusts carry embers up to 2 km ahead of the main fire front, starting new fires long before the flames arrive. Winds also fan existing flames, intensifying their heat and speed. While L.A.’s recent wildfire devastation was fueled by the Santa Ana winds, B.C. faces a similar threat as its coastal regions increasingly experience stronger wind systems enabled by warmer oceans.
For SSMUH properties, the danger lies not primarily in direct flames but more in the ember showers that can ignite roofs, eaves, or siding. You've read the news mention ember showers acting as a "blowtorch". A well-designed building form minimizes these vulnerabilities. SSMUH designs should aim for simple, compact shapes; complex structures with multiple peaks or recessed areas create opportunities for embers to gather. Roof valleys, for instance, are particularly prone to gathering debris that can ignite.
In addition to form, material choice and attachment play a critical role. Roofing such as standing seam metal, can resist both high winds and fire. Reinforcing cladding connections with wind-rated fasteners and ensuring tight seals around roof edges and siding joints are practical measures to prevent materials from detaching during extreme wind events.
Emergency Preparedness and Passive Fire Safety in SSMUH Design
In a wildfire emergency, while evacuation is critical, the building itself must act as a fortress against fire. Passive fire safety measures do not rely on human intervention or external firefighting efforts, making them particularly valuable in high-risk areas and helpful to where water supply or firefighting resources are stretched or scarce. Fire-rated walls, floors, and ceilings help contain a fire to its point of origin, limiting its spread across units in SSMUH buildings. This compartmentalization ensures that even if one unit is compromised, the rest of the building can remain intact.
Mineral wool insulation plays a pivotal role in this strategy. Unlike traditional foam insulation, which can emit toxic fumes when burned, mineral wool is noncombustible and capable of withstanding temperatures over 750°C. It not only slows heat transfer but also acts as a barrier, preventing fire from breaching walls and spreading into the structure.
In addition to insulation, fire protection for doors and windows is crucial. Fire-rated doors can withstand flames for up to an hour, providing critical time for occupants to evacuate and for fire crews to respond. For windows, triple-glazed glass with tempered panes resists thermal stress which prevents fire coming through the windows, but external fire shutters work even better. Combining these passive safety features ensures SSMUH buildings are equipped to withstand severe fire scenarios with minimal reliance on external help.
Defensible Landscaping for Multiplex Properties
Creating defensible space around a building is one of the most effective ways to protect it from wildfire. This involves strategic landscaping to reduce the amount of combustible material near the building. In suburban or rural properties, this often means maintaining a perimeter of gravel or paving stones, yet for urban multiplexes on smaller lots, similar principles apply.
Gravel beds, noncombustible pavers, or concrete walkways should extend at least 1.5 meters (5 feet) from the building’s foundation. Pavers are preferred since they are easier to sweep clear of fallen vegetation regularly and also allow rainwater to infiltrate the ground at other times. This noncombustible zone prevents embers from igniting flammable ground coverings such as mulch.
Vegetation must also be carefully selected and maintained. Coniferous trees and shrubs, which contain high levels of resin, should be avoided within 10 meters (30 feet) of the structure, as they act like torches when ignited. Instead, opt for fire-resistant plants such as succulents, lavender, or ornamental grasses, which require minimal watering and are less likely to ignite. Trees that are close to the building should have their lower branches trimmed to at least 2 meters (6 feet) above the ground to prevent fire from climbing into the canopy.
For urban multiplexes, maintaining clean, debris-free gutters and roof surfaces is vital, as these areas often collect leaves and twigs that can ignite from ember showers. Regular inspections and timely maintenance ensure that landscaping remains a defensive asset rather than a liability.
Fire-Resistant Roofing and Cladding Solutions
Roof and wall materials are the first line of defense against wildfire, making the choice of noncombustible materials essential. For roofs, standing seam metal is one of the most durable and fire-resistant options. It not only resists ignition but also allows embers to slide off rather than accumulate. Concrete tiles are another excellent choice, offering both fire resistance and aesthetic flexibility, as they come in various shapes, sizes, and colors. Rubber shakes are a less common but third alternative with some fire-resistive quality.
For wall cladding, fiber cement products such as HardiePlank or Nichiha panels provide a balance of fire resistance, affordability, and design versatility. Metal panels, while more expensive, offer a sleek, modern appearance and are nearly impervious to fire. Note that aluminum composite panels are not fireproof, and even "fire-rated" aluminum composite panels have limited resistance to fire. Traditional materials like brick or stone remain timeless options, providing not only superior fire protection but also a high level of thermal mass, which helps regulate indoor temperatures.
Homeowners and developers should consider the lifecycle costs of these materials. While some options, such as metal or stone, have higher upfront costs, their durability and minimal maintenance needs often make them more cost-effective in the long term. Additionally, newer products like cementitious stucco or ceramic-based coatings allow for modern or traditional aesthetics without compromising fire safety. Proper installation, including fire-resistant flashing and tightly sealed joints, enhances their effectiveness.
5. Effective Fire Barriers and Airtight Construction
Fire and embers often infiltrate buildings through small openings, making airtight construction and fire barriers critical in wildfire-resistant design. Airtight construction ensures that every seam, joint, and connection is sealed, leaving no path for embers or smoke to enter. This approach significantly enhances the building's overall fire resistance while also improving its energy efficiency.
Installing fire-rated shutters or fine-mesh screens over windows and doors is a key defensive measure. These features can block radiant heat and prevent embers from shattering glass or entering the home. For vents, which are usually necessary for proper airflow, 3mm (1/8-inch) metal screens provide an effective barrier against ember intrusion without compromising ventilation.
Modern HVAC systems, such as heat recovery ventilators (HRVs) and energy recovery ventilators (ERVs), are essential in maintaining indoor air quality during wildfire events. These systems filter out particulates and smoke while recirculating clean air throughout the building. When paired with fire-rated insulation and exterior thermal barriers, they create a multi-layered defense against both heat and smoke.
Attention to construction details is crucial. For example, using fire-resistant gaskets around windows and doors ensures a tight seal, while encapsulating mass timber elements with fire-rated drywall provides additional protection. Together, these measures create a robust defense that allows SSMUH buildings to remain habitable and safe, even in the face of extreme wildfire conditions.
My Approach
I excel in designing high-performance buildings that integrate advanced wildfire-resistant techniques. My expertise spans residential and multifamily construction, allowing me to craft SSMUH properties that stand strong against fire threats. Through my proprietary SAPPHR Strategy, I deliver sustainable, aesthetically pleasing, and fire-resilient designs tailored to each client’s needs.
When picking an architect to design your multiplex in Metro Vancouver or elsewhere in British Columbia, look at the process. My process begins with a comprehensive site assessment to identify fire risks and determine the best strategies for fire resistance. I integrate fire-rated materials, airtight construction, and passive safety measures to ensure my buildings surpass building code fire safety standards. I provide innovative solutions that offer both safety and beauty.
Imagine a wildfire tearing through your community. As you wait in an emergency shelter, news arrives that your SSMUH building has survived the blaze. While other homes lie in ashes, your property stands unharmed, its fire-resistant design protecting your investment and ensuring a place for families to return.
Now picture the opposite: your building reduced to rubble, leaving multiple families displaced and their lives in chaos. The loss of homes, possessions, and stability is devastating. Without fire-hardening measures, this scenario becomes far more likely. Take action now to protect your property and the people who rely on it.
With the right design, your SSMUH project can withstand the growing threat of wildfires.
You can download my SAPPHR Strategy guide using the link below. Inside, you'll find the overview of the methodical procedure I use for projects.
If you feel ready to move ahead with a multiplex project and want to see this process at work, please contact me for a free 30-minute Diagnostic Session using the button below.
DISCLAIMER:
The information included in this article is to an extent generic and intended for educational and informational purposes only; it does not constitute legal or professional advice. Thorough efforts are made to ensure the accuracy of the article, but having read this article, you understand and agree that Daniel Clarke Architect disclaims any legal liability for actions that may arise from reliance on the information provided in this article. I am an architect in BC, but readers are recommended to consult with their own architect on their specific situations before making any decisions or exercising judgement base on information in the article.
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