The exterior view of a house rebuilt in Santa Rosa after a fire showing white exterior walls, housing a roofed garage with a car parked outside the garage door at the center and well maintained shurbs and lawn to the right.

Each year, California wildfires burn with increasing intensity. As more families flock to fire hazard areas at a time when survivors attempt to rebuild their damaged homes, the inevitable question is: how can I build a home that’s fire-resistant? 

While fully fire-proof houses may be a thing of the distant future, a home’s fire resistance can be augmented with several attested strategies.  

If you want to stop fires from finding their way into the structure or interior, you must keep these burning debris out of the home’s cracks and openings.

Unlike fires that originate inside a building and quickly spread to the plethora of combustible items, wildfires tend to sweep over a home quickly as they’re driven onward by winds. The fewer the flammable materials in their path, the faster the attack will be over. If the flames are kept out of the interior while the fire passes, the extent of damage can be reduced substantially. With this in mind, a fire-resistant home must be designed such that: 

  • contact between the flame and the exterior is minimized
  • there are no openings which could let embers inside the building

  • the exterior can withstand prolonged exposure to the flames without failing and letting the flames inside

  • active fire suppression systems will get activated whether automatically or manually, and work to effectively ward off the flames

Creating a defensible space around the home, designing an envelope that won’t let in embers or fail when heated, and investing in fire protection and suppression systems are all effective methods for achieving the goals described above.

1. Create a defensible space

Driven by wind, flames travel over areas covered with combustible items, such as weeds, shrubs, and trees. Strategically landscaped spaces can protect your house from an approaching wildfire. Driveways, decks, patios, water features, and incombustible vegetation can all be used to form such a defensive perimeter. 

Driveways should be designed to accommodate fire crews and their equipment and to facilitate their firefighting efforts. If you’d like to add a patio, it’s best to avoid wood or composite decking. Except for Ipe, which has a Class A flame spread rating, most species of wood eventually ignite and burn when exposed to flames for a long time. Other visually appealing and flame-resistant options include stone or concrete pavers, and outdoor porcelain tile. 

Just because your outdoor space is designed to keep fires out, doesn’t mean that you have to compromise on aesthetics. You can do this by placing fire-resistant plants in your outdoor space. Luckily, California residents have plenty of beautiful, fire-resistant plants to choose from. Most of these are drought resistant too. Here are some options readily available in the state: 

  • French Lavender
  • Red Monkey Flower

  • California Fuchsia

  • Sage

  • California Lilac

  • Society Garlic

  • Ornamental Strawberry

  • Yellow Ice Plant

  • California Red Bud

  • Coreopsis

Be sure to keep your lawn irrigated and clear away dead plants regularly.

To deny flames any source of fuel, install steel stairs and guardrails on the home’s exterior. It goes without saying, but don’t store firewood, mulch, or anything combustible immediately under the deck or immediately outside your house.

2. Don’t let the embers inside 

As a wildfire advances through your property, it may leave behind embers and spot fires. If you want to stop fires from finding their way into the structure or interior, you must keep these burning debris out of the home’s cracks and openings. Common places where embers get trapped include: 

  • roof vents
  • attic vents

  • soffit vents

  • bathroom vents

  • kitchen vents

  • dryer vents

  • between roof shingles 

  • under garage doors

  • eavestroughs 

  • louvers

A square ducted vent on a ceiling that is one of the places where embers are trapped

Many of these features are essential for comfort, and, understandably, you wouldn’t want to exclude them from the design. That said, you have to take special measures to protect these openings. The code-mandated 1/8-inch screens might satisfy your building officials but may fail to keep out the smallest of embers and brands. Cover these penetrations with the tightest mesh possible and use fire dampers where you can. Ember-resistant vents are available on the market and could make a good alternative, provided that your local building code allows them; confirm with your building officials. Finally, see to it that your garage doors have a tight fit when closed, as firebrands and embers can easily be blown under a loose-fitting door. 

3. Design a fire-resistant envelope 

Your home’s envelope - its protective outer skin - comprises cladding, roofing, doors, windows, gaskets/sealants, and insulation. These elements work in unison in keeping out water, moisture, radiant heat, and preventing air movement. In the fire-prone regions of California, they also protect your home’s interior from wildfires. While incombustible landscaping and ember-resistant openings can go a long way in keeping fires at bay, if any envelope components were to fail in the heat, the flames would inevitably work their way inside.

The fire-resistance of an envelope starts with the right cladding materials. These should not be flammable, and must not fail easily when subjected to high temperatures. Ideal cladding materials include: 

  • brick
  • adobe

  • stone

  • concrete

  • metal siding

Certain parts of the envelope require special consideration. For example, a flat roof can harbor burning brands until the roofing material ignites. To prevent this scenario, install a Class A fire-resistant roof as your line of defense. Undersides of balconies, under-floor areas, and roof soffits can trap flames and suffer exposure to severe temperatures, potentially affecting the home’s structural integrity. Again, all envelope materials should be free from nooks and crannies that may house embers.

Glazing is also vulnerable, as glass typically fails quickly when heated. For maximum protection, use Insulated Glazing Units (IGUs) with tempered glass. An IGU typically consists of 2 or 3 panes of glass, and each pane provides a few additional minutes of fire resistance. Because it’s tempered, the glass is better suited to withstand heat. 

4. Fire protection and suppression systems 

The California Residential Code already requires automatic fire sprinklers for new one- and two-family dwellings. If you’re building in a location where wildfires are a threat, a sprinkler system can prove useful beyond your home’s living areas. Install sprinkler heads on the roof, and over decks or patios around the house, as an added safeguard against approaching wildfires. 

While tempered IGUs will fare better in a wildfire than regular, single-pane glass, they’ll still be the weakest link in your home’s defense. Consider installing automatic rolling shutters over glazing. These rolling doors can be concealed in soffits above windows and deploy when a fusible link melts at a certain temperature. 

How Design Everest can help 

Whether your project involves a fire rebuild or new construction in a fire hazard area, our engineers can help with all aspects of civil, structural design, and MEP design. Contact us at (877) 704-5727 to discuss your project and receive a quote today.

Sources/References:
  • https://www.readyforwildfire.org/prepare-for-wildfire/get-ready/fire-resistant-landscaping/
  • https://www.nfpa.org/-/media/Files/Firewise/Fact-sheets/FirewiseFactSheetsImmediateNoncombustibleZone.pdf
  • https://www.nfpa.org//-/media/Files/Firewise/Fact-sheets/FirewiseHowToPrepareYourHomeForWildfires.pdf
  • https://www.fema.gov/media-library-data/20130726-1652-20490-8008/fema_p_737_fs_10.pdf
  • http://www.energy-design-tools.aud.ucla.edu/FIRES.html
  • https://designeverest.com/services/fire-rebuild/
  • https://designeverest.com/blog/guide-to-rebuilding-building-after-fire/
  • https://designeverest.com/mep-design-mechanical-electrical-plumbing/
  • https://designeverest.com/services/new-custom-home/
  • https://up.codes/viewer/california/ibc-2018/chapter/new_7A/sfm-materials-and-construction-methods-for-exterior-wildfire-exposure#new_706A.2
  • https://www.embersout.com/

*Note: The content published above was made in collaboration with members of Design Everest.

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