Design Your House or SSMUH / Multiplex For Storms

Daniel Clarke
4 days ago
7 min read

Not being prepared for power outages and heavy rains or freak snowfall can leave several families being without electricity and heat, and protection against wind-driven rain compromised.

Street littered with debris after storm, flanked by damaged houses. Puddles reflect the cloudy sky. Autumn trees line the road.

I spell out here a few things that will protect your families or renters from an uncomfortably or dangerously cold home during power outages and protect the multiplex or house against damage to the exterior.

Most homes are not designed to function comfortably when facing storms of the severity which is becoming increasingly frequent. A SSMUH / multiplex generally doesn't require a diesel-powered electrical generator for backup power, so when the power goes out in a multiplex, several families are potentially without heat during cold weather. Siding and roofing materials also are not designed to remain fully intact when subjected to the sustained wind strength of increasingly common storms.

Unless you live in the core of an urban centre, your electrical service is vulnerable to windstorms, and your house or multiplex must be able to handle the deluges that typically accompany the high winds.

Recent Devastation

A little while ago, there was a big windstorm (CBC link here) preceded by and followed by atmospheric rivers. By the following morning, a significant portion of the Lower Mainland and Vancouver Island were without power. Electrical lines had been downed by trees blown over and large branches falling. Trees are fundamental to the health, temperature moderation, and environmental soundness of an area, and overhead power lines are less expensive and easier to maintain than underground electrical services.

Fallen tree branches on a rainy street, with cars driving in the background. Overcast mood, grey tones, and wet surfaces dominate the scene.

Recently, on the East Coast, a severe snowstorm (CBC link here) resulted in power outages during very cold weather. Even some homes with generators would have been incapacitated. Key roads had become impassable, so resupply to gas stations was hampered, and several had run out of fuel. High winds increase the pressure on a home's walls, forcing in more cold air and pulling out more warm air.

Earlier this autumn, there was a severe windstorm in Southeast BC (CBC link here) which resulted in widespread power outages and flooding in various regions. Landslides closed highways, making BC Hydro restoration work difficult and requiring some trapped motorists to be rescued.

Real Risks and Attainable Solutions

Power Loss

The case for resilience to power outages is serious and applies to everyone. A house or multiplex heated by a natural gas furnace is still susceptible to power outages since the furnace blower fans are still electrically powered. In 2021, disaster in Texas resulted simply from cold weather without adequate heating. In most homes in North America, plumbing pipes are located in exterior walls as well as interior walls. If the outer portion of the building cools to below freezing, the pipes may freeze and destroy the walls.

Snow-covered street lined with houses and trees. Snow piles high on the ground and rooftops, creating a calm, wintry atmosphere.

Exterior Insulation

Thermal insulation that sits outside the plywood of the exterior walls allows services (piping, electrical wiring, in-wall ducts) to be placed in the stud spaces without compromising the insulation value; the insulation still fully protects piping from freezing. Furthermore, the more insulation you can provide in your walls, the longer it will take for the home to lose its heat if it loses its power.

A-frame house in snowy landscape at dusk, warm light glowing from windows, surrounded by snow-covered trees and bushes; serene winter scene.

Exterior continuous insulation is also more effective than insulation that is stuffed in between the wall studs. For example, "R22" fibreglass batt insulation in a wood stud wall results typically in a wall whose effective insulation value is only around R12-R13 - or potentially less if you have larger windows. On the other hand, if you place R20 rigid insulation boards on the exterior and screw through the boards to the studs, the effective insulation value is around R18-R19.

Wind and Rain

Asphalt shingles and wood shakes are designed to remain in place in high winds, but they are susceptible to being ripped off if the winds are higher or sustained gusts batter the roof. Freakishly high winds and rain can also compromise your home's weather protection directly. Shingles and shakes are water-resistant, but enough rain for a long enough period without adequate time and sun to dry out, will allow water into the roof structure. Strong gusts can lift the shingles and tear them out, further exposing the structure to rain.

A white house with a damaged roof shingles and debris in the yard, under a cloudy sky. Leafless trees and scattered branches surround it, suggesting storm aftermath.

Metal Roofing

Metal roofing is the straightforward design answer to storm-proofing the roof. It handles suction, uplift, and driving rain far better than anything made of overlapping pieces. In a multiplex, where several families depend on a single large roof, reducing the odds of partial failure is worth far more than the marginal cost increase. Metal roof panels typically can resist positive and negative wind pressure far above what shingles and shakes can. A good metal roof system is held in place by concealed clips which are engineered to provide the pullout strength that resists the wind. Metal roofing also is impervious to rain; it will never become soaked.

Modern stone house with black metal gable roof in rain, surrounded by autumn trees. The mood is serene with earthy tones and rain streaks visible.

Heavy Rains

Rainfall that is sufficiently heavy can overwhelm your home's foundation drainage system (weep tile). Rainwater gradually saturates the soil, and the buildup of hydrostatic pressure will push water through tiny cracks in your foundation where there's a gap in the dampproofing. Wet soil against the foundation can even overcome the dampproofing's ability to keep out water. For basements or even foundations a little below the ground surface, this is a disaster. In places such as Port Moody or West Vancouver where the adjacent mountainside collects a large amount of rainwater, the risk is greatest.

Foundation Drainage

The first change is the size of the foundation drain. Although 4" and 5" diameter are common, 6" provides ample capacity and better avoids blockages. Drain tile of any size must be properly wrapped in filter fabric and covered in appropriately sized clean gravel. Placing a 5' wide strip of clean gravel around your home, which extends to the bottom of the foundation, improves the drainage of your property and helps prevent water buildup. It also helps prevent your home's siding from catching on fire during a wildfire. French drains and rain gardens are rainwater management techniques that create design features.

Closeup of rain garden, Wildflowers line a rainy street with small pebbles and flowing water. Houses blur in the background, creating a serene and moody scene.

I discuss flood prevention strategies extensively in my article, Designing a Flood Proof House, Part 3 (link here).

Foundation Waterproofing

99.9% of homes' foundations are protected with only dampproofing, and most builders will assure you that this is adequate. Waterproofing membranes are more expensive than dampproofing, but they are better and safer in two important ways. First, nearly every concrete wall will have or will develop at least minor cracking. Waterproofing stretches more and is continuous across the cracks. Second, waterlogged soil against dampproofing will result in water eventually moving into and through the concrete. True waterproofing membranes hold back water indefinitely; they are used to line swimming pools.

House with damaged deck over a collapsed streambank, surrounded by debris and green foliage. Reflective water creates a somber mood.

Intense rainstorms occasionally overload the stormwater sewers, combined sewers, and even sanitary sewers; and water will be running across the surface of the ground. Robust drainage isn’t just a “nice to have” in a wet climate; it’s the only thing keeping heavy rainfall from turning your foundation into a water inlet. thoughtful site grading, better gravel, bigger weep tile, proper fabric wrap, and true waterproofing all work together so the building stays dry even when the neighbourhood doesn’t.

Trees

Trees are used by smart architects as a design tool, not just as decoration. A deliberate mix of small and mid-sized trees helps on two fronts. First, they break up the force of gusts that try to lift siding or drive water into the cladding. Second, their root systems keep the surrounding soil in place during heavy downpours. When soil around the foundation washes away, you expose more of the concrete to cold air, increasing heat loss. Frost cover is reduced, cracking or settlement may occur - more likely in a larger, two- or three-storey multifamily building than in a smaller single-family house.

Even modest deciduous trees can take the edge off wind pressure and provide meaningful shade in summer. The goal isn’t to plant one heroic giant that becomes a liability in storms; it’s to build a varied, well-spaced canopy of medium-scaled trees that act as low-tech, self-maintaining wind and rain buffers.

Make This Climate-Resilient Solution Yours

I’ve spent years detailing multifamily buildings, researching the resilience of Passive House single and multi-family homes, and studying the real-world failures of other buildings - the roofs peeled back by suction, the walls soaked from sideways rain, the foundations that collapsed once the soil turned to soup. Just as important are the buildings that stayed habitable while everything around them failed. The lessons are consistent, and they’re not complicated; they just require treating storms as a design input instead of an afterthought.

My approach for managing storms is straightforward: tighten the envelope with durable finishes, protect the occupants in cold weather by using exterior insulation, design drainage that works when the ground is already saturated, and use trees as part of the wind and rain strategy. None of this is glamorous, but it’s the difference between a multiplex that fears the next outage and one that protects the people living inside it.

A multiplex designed the way that single-family homes have traditionally been - and still generally are - designed loses heat quickly, leaks under pressure, and starts accumulating expensive problems as stormy weather adds up. Good design widens the gap between those two outcomes more than most people realize.

A well-designed building that follows my UltraHome model holds its heat after the power drops, keeps water where it belongs, and shrugs off the kind of wind that sends tarps flying in the neighbourhood. Families stay safe and inconvenienced rather than cold and scrambling.

The SAPPHR™ Strategy is a framework and methodical progression through pre-design and design to delete assumptions, optimize design, and unnecessary construction work. You can download a copy of the SAPPHR™ Strategy client manual at the link below.

>>> DOWNLOAD CLIENT MANUAL <<<

For those of you who want a climate-resilient multifamily home, I offer a free, 30-minute consultation - the Diagnostic Session. You're not just designing a home; you're creating a refuge that a number of families will look to for safety and comfort during inevitable natural disasters.

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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 Inc. 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.