Home Hardening Video Series: Roofs & Gutters
Highest Priority: Your roof has the most exposure to falling embers. Making your roof firesafe can go a long way to protecting your home if wildfire comes near your property.
HOW HOMES IGNITE
Homes ignite in one of three ways: embers/firebrands, radiant heat exposure or direct flame contact. An example of an ember ignition is when wind-blown embers accumulate on combustible materials such as a wood shake roof. An untreated wood shake or shingle roof covering is the greatest threat to a home.
Roof and Gutter Cleaning Tips
- Be Safe
- Hire a professional if you are unsure or lack the proper tools. Some roofing materials can be damaged if you walk on them, and every roof poses a fall hazard.
- Always use a sturdy, well-footed ladder to reach your roof and gutters.
- Don’t clean your roof alone. Be sure there is someone with you, on the ground, to help when needed.
- Check your roof. Is it well maintained? Is the roofing made from a fire resistant (Class “A”) material like tile, composite shingles, or tar and gravel? It can be difficult to tell whether you have a Class “A” fire-rated roof, unless it’s made of an obviously noncombustible material, such as tile. If you are not sure about your roof, schedule a professional roof inspection to find out.
- Always keep your roof clean of debris. Clean it as often as necessary during fire season. Remember: even a tiny handful of leaves is enough to burn your home!
- Check your gutters. Metal gutters are safest, and all gutters must be maintained completely free of leaves, needles, and vegetation during fire season (and the rainy season too, or course). Like the rest of your roof, you may need to clean them more often during the summer if you live in an area where leaves are likely to fall onto your roof.
GUTTER SAFETY BULLETIN!
Gutters play a role in providing a means of collecting and directing rainwater from the roof into downspouts, and then away from the house. This helps reduce the amount of water in the soil that can enter the crawlspace or basement and result in moisture-related performance problems such as those from mold and wood decay fungi.
Combustible debris such as leaves and pine needles can accumulate in gutters, especially from nearby or overhanging trees. Due to difficulty in accessing upper stories of a home, gutters two and three floors high are even more problematic, since they will be difficult to clean out on a regular basis. If ignited, combustible debris in the gutter will expose the edge of the roof covering, typically the fascia and or roof sheathing. Depending on the condition of the wood and presence (or absence) of metal flashing at the edge of the roof, debris in the gutter may make it easier for fire to enter the attic. Metal flashing at the roof edge will provide additional protection to the roof edge and therefore is a recommended detail.
As shown in the photograph below, the roof deck boards in this eave overhang area are decayed. These boards would be more easily ignited if debris in the gutter ignited, in this case, angle flashing at the roof edge was used, but the poor condition of the roof would still make this a vulnerable area.
Metal gutters have been recommended over plastic gutters in fire hazard areas. Embers will ignite accumulated debris in any gutter. Metal gutters will stay in place, and therefore the resulting fire will continue to burn at the roof edge. Vinyl (or plastic) gutters will quickly detach and fall to the ground. The debris and combustible gutter material will continue to burn, igniting any combustibles (mulch, vegetation, wood piles) and potentially any combustible siding. Flames can be high enough to impinge on windows. If you have vinyl gutters, a noncombustible (or low flammability) zone near the home is critical (e.g., use noncombustible rock mulch and carefully selected and maintained vegetation). If you have metal gutters, make sure the components at the roof edge are well maintained. Regardless of the gutter material, clean out debris in the gutter on a regular basis.
Gutter guards or covers can be installed over or in your gutters. When properly installed (and maintained), these can reduce the amount of vegetation litter and debris that accumulate in your gutter and therefore reduce the need to clean it. Some products can become dislodged over time, and they will have to be reinstalled when this happens. Some products can result in the accumulation of debris on the roof, behind the gutter. There are a number of commercially available products specifically intended for this purpose – just type gutter guard in a web-browser search engine to get an idea of the available products. To date, there isn’t a standard procedure to evaluate the performance of these products.
Note that some of the covers in the gutters on this roof have dislodged, and therefore no longer keep out debris. Gutter guards should be inspected regularly, and reattached when necessary.
The following photograph shows debris that has accumulated behind the gutter cover. This Class A roof covering will be able to handle the fire if this debris is ignited by embers, but because of the proximity to the roof edge, this debris should be removed from the roof.
It is possible that your home won’t have gutters. Although this will eliminate any ‘debris accumulation’ issue, it will result in a heavy rain load around your home, and depending on drainage, may contribute to moisture related problems.
ROOF COVERINGS AND ASSEMBLIES
Roof covering fire ratings are Class A, B, C, or unrated; with Class A providing the best performance. Common Class A roof coverings include asphalt fiberglass composition shingles, concrete and flat/barrel-shaped tiles. Some materials have a “by assembly” Class A fire rating which means, additional materials must be used between the roof covering and sheathing to attain that rating. Examples of roof coverings with a “by assembly” fire rating include aluminum, recycled plastic and rubber and some fire-retardant wood shake products. If a wood shake roof does not have the manufacturer’s documentation specifying the fire retardant, assume it’s untreated.
TILE AND ROOF COVERINGS WITH GAPS BETWEEN THE COVERING AND ROOF DECK
Flat and barrel-shaped tiles, metal, and cement roof coverings can have gaps between the roof covering and sheathing, which typically occur at the ridge and edge of roofs. These openings can allow birds and rodents to build nests with materials that are easily ignited by embers. Flames from this type of ignited debris can spread to the structural support members, bypassing the protection offered by a Class A rated roof covering. Plugging these openings between the roof covering and the roof deck, is commonly called “bird stopping”. Regularly inspect and maintain these areas.
WATCH A VIDEO OF WILDFIRE TESTING AT THE IBHS RESEARCH CENTER TO SEE HOW A HOME REALLY PERFORMS IN AN EMBER STORM. THEN, ANSWER THE QUESTION BELOW TO SEE HOW VULNERABLE YOUR HOME MAY BE.
How fire resistant is your current roof?
• The fire rating of a roof covering is either Class A, Class B, Class C, or unrated. An unrated roof is the most vulnerable – the most common example of an unrated roof covering is one made using non-fire-retardant treated wood shakes or shingles.
• Class A is the most fire resistant and should be the choice of anyone living in wildfire prone areas.
• Common Class A roof coverings include asphalt fiberglass composition shingles and concrete or clay tiles. Some materials have a “by assembly” Class A fire rating, meaning that additional materials must be used between the roof covering and the roof sheathing in order to attain the fire rating. Examples of roof coverings with a “by assembly” fire rating include aluminum, some fire-retardant wood shake products, and recycled plastic and rubber products.
• If you have a wood shake roof and do not have, or cannot find documentation from the manufacturer that specifies the fire rating of the wood shake, assume it is unrated.
• If you are not sure, or want to confirm your roof type, schedule a roof inspection by a roofing professional.
• If your home is located in a wildfire-prone area and your roof is unrated or if your roof is old and needs to be replaced, IBHS recommends that you install a Class A fire-rated roof.
Fire burning through to the underside of this roof covering assembly (into what would be the attic) indicates that, as constructed, this roof covering does not qualify for a Class A fire rating.
If needed, replace your roof covering
If your roof has reached the end of its service life, it should be replaced. IBHS recommends hiring a professional roofing contractor to replace or repair your roof covering.
If you have an untreated wood shake roof, the only solution for reducing your wildfire risk is to replace it with a rated roof covering. Regardless of your fire hazard, given that many Class A roof coverings are available, IBHS recommends installing a Class A covering if you are living in a wildfire-prone area.
The roof covering and edge are the most vulnerable part of a home. Because of its large, relatively horizontal surface, the roof has the most severe exposure to all elements, including sun and rain, and during a wildfire, embers. Because of these exposures, roof coverings tend to require more maintenance and typically have a shorter service life than other construction materials used on the outside of homes.
Fire ratings for roofs provide a measure of the amount of protection. Class A provides the highest protection and Class C the lowest. At a minimum, unrated roofs, such as an untreated wood shake roof, should be replaced by a rated roof. Class A roofs are commonly available and can be very affordable, so they can be well worth the cost. Regardless of roof type, it should be kept in good condition and free of combustible debris. Your local building and fire departments would know about any special requirements that may apply to your community.
Roofing materials can obtain a Class A rating based on the covering alone (a stand-alone Class A covering) or the covering and an underlying material used to enhance fire performance (Class A by assembly). The fire rating for roof coverings is determined by following a standard test procedure developed by the American Society for Testing and Materials (ASTM), called the Stan- dard Test Method E-108. This test evaluates flame spread over the roof covering, the ease with which fire can penetrate through the roof (and into the attic or ceiling space), and the ember generation potential of the roof covering. If flame spread is too large, or if fire penetrates through the roof covering and underlying construction materials, the covering cannot be considered Class A.
When using an assembly-rated Class A covering, make sure that all installation instructions are followed and all specified materials are used. The fire performance of the assembly may be reduced if installation procedures are modified or materials other than those specified are substituted
Many noncombustible roofing materials receive a stand-alone Class A rating by meeting the noncombustible definition as provided in the building code; therefore, they do not need to be tested to the ASTM E-108 standard and given
a fire-resistant rating (e.g., a Class A, Class B, or Class C fire-resistant rating). An exception to this general rule is an aluminum covering. Because of its low melting point, it must be tested. Installation instructions will include use of an additional material under the aluminum covering in order to receive the Class A (by assembly) rating.
Wood shakes treated with a pressure-impregnated, fire-retardant chemical can achieve a Class A assembly rating. In California, wood shakes treated with a fire retardant must pass a natural weathering exposure test to be approved for use by the Office of the State Fire Marshal (OSFM). Wood shakes approved for use in California must be registered with the OSFM Building Materials Listing Program. In some communities within and outside of California, wood shakes and shingles treated with fire retardant are not allowed.
A complex roof provides an additional level of vulnerability. The term complex indicates that there are a number of horizontal- to-vertical intersections on the roof that could make a Class A roof more vulnerable to wildfire, and in particular to an ember exposure. From a fire performance perspective, these intersections provide collection points for windblown debris (e.g., pine needles and other vegetation), debris from overhanging trees, and—during a wildfire—windblown embers. These locations are also where different construction materials with different fire vulnerabilities will be present on the respective surfaces. If ignited, the flames from the burning vegetative debris would provide a flame contact exposure on the siding material, the roof sheathing or soffit material, or even a window. The vulnerability of these components will depend on material selection and other design considerations. Particularly with a Class A roof, it will be the fire resistance of the siding, sheathing, or window that will determine the vulnerability of the complex roof, not the roof covering itself.
Skylights typically cover a small portion of the roof, but they can still provide an entry point for wild- fire. Flat skylights contain tempered glass. Domed skylights have a plastic outer shell, usually with an inner layer of flat glass. In domed skylights that can be opened (i.e., they are operable), screening is sometimes used instead of the flat glass layer.
If you have an operable skylight, make sure it is closed during a wildfire in order to avoid the entry of burning and glowing embers. None of these configurations could pass a standard Class A fire exposure test used to evaluate roofing materials. To understand the potential vulnerability of your skylights, you should consider the slope of the roof, the location of nearby combustible materials, and the location of accumulated debris on and around the skylights. If your roof has a steep pitch, the skylight would receive more radiant heat from nearby burning vegetation or buildings, and glass may break or plastic deform. As always, it is better to keep debris cleared away from the skylight. Normally debris will not accumulate on the domed skylights, but it can on the flat skylights, particularly on lower sloped roofs. Debris can also accumulate at the edge of skylights. If that debris were to ignite, then the materials and connections at the roof-to-skylight intersection would be vulnerable, so it is important to clear debris on a regular basis. Vegetation management should also be part of your solution. Overhanging tree branches should be removed, since a broken branch could fall and break the skylight.