Mobile Home Wildfire Safety

During a wildfire, embers are the most common cause of ignition for both site built and manufactured homes. Embers are light enough to be blown through the air and can result in the rapid spread of wildfire by spotting (in which embers are blown ahead of the main fire, starting other fires). This wind-driven rapid spread scenario was observed, for example, in the 2017 Tubbs Fire in Santa Rosa and in the 2018 Camp Fire in Paradise. Should these embers land on or near your house, they can ignite nearby vegetation, accumulated debris, or enter the home through openings or vents.   Recent research indicated that two out of every three homes destroyed during wildfires were ignited either directly or indirectly by wind-dispersed, wildfire-generated, burning, or glowing embers and not from the actual flames of the wildfire. “Indirect ignition” implies either a radiant heat and/or direct flame contact exposure to the building from the combustible item ignited by the embers.

Near-home ignitions can subject some portion of a house to either a direct flame contact exposure (where the flame actually makes contact) or radiant heat exposure (the heat felt when standing next to a campfire or fireplace). If the fire is close enough to a combustible material, or the radiant heat is high enough, an ignition will most likely result. Even if the radiant exposure is not large enough or long enough to result in ignition, it can preheat surfaces thus making them more vulnerable to ignition.   In most mobile home parks the homes are sited relatively close together.   This can make mobile homes more vulnerable if adjacent homes are ignited by wildfire.

All homeowners should take action in four areas to reduce wildfire risk.

First, prepare yourself and your family.   Make a disaster plan, sign up for alerts and warnings, know your evacuation routes, pack a go bag, make a plan for your pets.

Second, create defensible space around your home.  The first five feet around the home should be clear of all combustibles.   In most mobile home communities in Marin, homes may be located close to each other.  When there is sufficient space between homes, be sure to clear dead grasses, weeds, plants and foliage within 30 feet from your home.   Limb up trees and create space between plants.   Do not use highly flammable mulches like gorilla hair. Any kind of flammable mulch product (i.e., all bark mulch products) should be avoided in areas close to the home.

Third, take action to harden your home.  Mobile homes sometimes have decks which must be protected from embers.   There should be no combustible materials under decks or the home itself. Make sure decks are properly screened (from the edge of the deck, vertically down to the ground) with corrosion resistant ⅛-inch mesh or smaller metal screening to minimize ember intrusion in the area under the deck.  If there is a fence, make sure there is a noncombustible section that connects to the home. That could be something like chain-link, hog wire, or iron.  The immediate solution, if you are evacuated in the event of a fire is to prop the gate open to create a break in the fence. If you think of the fence like a candle, we want to break the wick so it can’t burn any further.

Make sure the area around the skirting of your home is tidy and free of brush and debris. Keep the roof clear of trash and leaves.

Fourth, consider becoming a firewise community.   Mobile home parks tend to be community oriented.   Neighbors helping neighbors is a great way to prepare.

Vinyl is installed on over 30% of all new homes making it the most popular siding choice for both (mobile) manufactured homes and site-built homes.  As vinyl is a plastic material when exposed to a radiant heat or flames it will readily deform and melt, and would therefore not provide protection to your house.

An alternative to vinyl siding, fiber cement, a mixture of cement, sand, and wood fibers, has a high fire resistance rating. Fire resistance is a factor in the durability of the product.  Many fiber cement products carry a Class A flame spread index, the highest level possible.  Additionally, they slow fires from spreading into buildings and damaging property.

Steel siding, which is now more common, is a good choice for siding.  Metal, in general, is fireproof. They do not catch fire or spread it. However, aluminum siding can melt if exposed to high-temperature flame such as a burning juniper bush.    The melting point of aluminum is ~1200 F. That of steel is ~2500 F. Vinyl is ~200 F.

Brick and stone veneers over wooden frames reduce the risk of fire enormously. It is important to use solid brick or stone, not a thin veneer that has the appearance of brick or stone.

When making the house exterior fire-resistant, house owners forget about the trims, soffits and windows”. Yes, the siding takes most of the space on the exterior walls. But if the trims do not provide comparable performance, they can be the vulnerable component on your home.

Pay attention to the materials it’s made from. Check if they are noncombustible or not. If the trims are made with flammable material options, try to reinstall the better product during your next renovation.  Make sure all openings are well sealed. Fiber-cement trim products are readily available.

Modifying or refurbishing a manufactured home to meet all the recommended wildfire resistant features can be an expensive, albeit very worthwhile endeavor. As an alternative, homeowners may want to consider the prospect of replacing an older fire-prone home with a new fire resistant home. All new manufactured homes placed in designated state or local fire hazard severity zones must conform to Title 24, Part 2, Chapter 7A in order to qualify for HCD building permits.

The costs for choosing either alternative are in constant flux due to numerous factors, but one may be pleasantly surprised at how little the difference may be considering the benefits of a new home.

The California wildfires have sparked much of the recent debate over sprinkler systems  The function of an exterior sprinkler system is to minimize the opportunity for ignition by wetting the home and surrounding property. Sprinkler systems should be able to protect a home against the three basic wildfire exposures: wind-blown embers, radiant heat, and direct flame contact.

Post-fire assessments have shown exterior sprinkler systems can be effective in helping a home survive a wildfire, but potential issues exist with their use. These issues include:

• The water supply should be adequate to deliver water when needed, for the time embers could threaten a home. This period could be up to 8 hours.
• Check with your local fire department if your sprinkler system uses water from a municipal supply; they may have suggestions to help minimize water consumption.
• The effectiveness of a sprinkler system is questionable when a neighboring home is burning since this would result in extended radiant heat and/or contact exposure to the home.
• Some of these systems can be activated manually or by an automated device, such as a sensor that detects heat or flame, or by an SMS-enabled cell phone. The ability of these systems to activate based strictly on an ember exposure has not been determined. Since wind-blown embers can be transported for up to a mile from the flame front of a wildfire, this may be a limitation.
• The most threatening wildfires occur during high-wind events and the homeowner should consider how the distribution/transport of water droplets may be influenced by elevated wind speeds. The water droplets will likely not land in the same locations as on a windless. WInd will also result in evaporation losses, also reducing the effectiveness of the applied water.
• Water spray may not protect the undersides of vulnerable structures such as eves or beneath the home.
• Water spray landing on a hot window can break the glass and expose the home interior to ignition.

Given the potential issues regarding performance, it’s recommended that use be a supplement to, and not a replacement for, already proven mitigation strategies, such as the reduction of potential fuels throughout the home ignition zones, along with removal of roof and gutter debris, and use of noncombustible and fire/ember ignition resistant building materials and installation design details

There are many benefits to living in mobile homes, but residents should be aware of some safety concerns unique to these structures. While they are vulnerable to all the same hazards found in permanent structures, mobile homes are built of lighter materials and they may not be fixed to the ground with the equal reinforcements.

Many mobile and manufactured homes in California have been retro-fitted with tie-downs to take advantage of a substantial discount offered by the state’s earthquake insurance coverage. Only new Chapter 7A homes are engineered to carry the weight of cement composite walls plus the required interior sheetrock without a perimeter foundation. Retrofits with these additions are permitted by HCD provided they are also retrofitted with perimeter foundations as per HCD specs.

The primary cause for the increase is that fire spreads more rapidly through mobile homes due to the small space and light construction, while the structure itself intensifies the heat and smoke buildup. In addition, most mobile homes have fewer safe exits than a traditional home.

The number one cause of accidental mobile home fires is inadequate maintenance of the home’s mechanical system. Other frequent causes include carelessness and accidents.

Several mechanical systems in a mobile home require maintenance. These systems include heating equipment such as furnaces, flues, fireplaces, space heaters, wood stoves, water heaters, kitchen stoves, as well as electrical systems and electrical appliances.

Storing all matches and lighters out of the reach of children can prevent a tragedy. Fires caused by a mobile homeowner’s carelessness, such as a grease fire or a fire that started because flammable liquids were stored inside the mobile home, are also preventable.