In this section, we discuss the flat or sloped covering over your home. This would include the living space, garage (if covered), and deck (if covered).
Your roof and edge components (such as your gutters) are arguably the most important part of your home in terms of making it safer from wildfires. While your home may only be subjected to the flaming front of the wildfire for a few minutes, your roof (and the rest of your house) could be subjected to airborne glowing or burning embers for a few hours as the wildfire approaches and burns through the area where you live.
Roofs: Potential Problems
How well your roof performs during a wildfire will depend on a number of factors, including:
1. The roofing material used.
2. The age and condition of your roof.
3. The 'complexity' of your roof (that is, how many levels and wall/roof intersections you have, and how much debris can collect there).
4. Gutters and other 'edge of roof' factors.
5. Vents and other penetrations in your roof.
As you can tell from this list, how your roof performs will depend not only on the roof covering, but also on intersections where your roof connects to other materials. These connections are often at a horizontal to vertical intersection.
The fire rating of roof coverings is determined for all materials used in code-compliant housing, and will be classified as Class A, B, C, or 'unrated'. Class A provides the best fire resistance, so for the best protection for your home, you should have a 'Class A' fire-rated roof covering. Information regarding Class A roofs is given in an Appendix H: Roof.
Every thirty years or so, you will have the opportunity to select a new roof covering. In the meantime, one of the most important jobs you have is inspecting your home and near-home vegetation, and performing needed maintenance. The standard tests to determine fire performance are conducted on new covering materials (the exception being fire retardant treated shakes that must also be evaluated after natural weathering). An older roof may not perform as well as a fire-resistance membrane. It will be up to you to make sure your roof covering is inspected and maintained, and replaced when needed.
When new, this asphalt composition roof covering has a Class A rating. The older and weathered roof may not provide the same protection from wildfire, and may also be more vulnerable to water leaks.
Another critical inspection and maintenance item for your roof will be to remove of debris (needles, leaves, and other combustible material) from collection points on your roof (for example, nooks and crannies), and from your gutters. Ignition of debris in these locations can ignite other roof components besides the roof covering - components that don't perform as well as your Class A roof. These components include the underside of the roof , and exterior siding. Debris that accumulates at the inlet to roof Vents can also ignite during a wildfire and enter the attic, potentially igniting other combustible materials in your attic.
If ignited, the debris on this roof would expose the underside of the overhanging roof, or the exterior siding. Both of these components are potentially more vulnerable to flame and ember exposure than a Class A asphalt composition shingle roof covering.
Vertical walls adjacent to the roof can accumulate combustible debris, typically leaves and needles. The ignited debris can expose the exterior siding, in this case wood shingles, and potentially the underside of the roof.
If ignited, debris in this gutter would expose the roof edge, with flame and embers potentially getting under the roof covering.
Pine needles on this non-fire retardant treated wood shake roof can easily be ignited, with flame and embers entering the attic through this 'through-roof' vent.
A through-roof vent can provide a "backstop" that can serve to accumulate wind-blown debris. If ignited, the burning debris can easily enter your attic.
Wind-borne debris can accumulate in the ends of this clay tile barrel roof covering. If accessible, birds can also build nests in the space between the roof sheathing and the bottom of the tiles, also providing combustible debris that is easily ignited if embers are driven into this area (under the tiles).
The ends of this clay tile barrel roof were covered by a cut-to-shape metal strip, but it has become disconnected, or was never properly installed. Embers can easliy enter these openings.
Skylights should be constructed with two layers of glazing. Another likely exposure for a skylight would from an impact of an ember, or other object lofted during the wildfire. For best performance, skylights should consist of two layers, with one of them consisting of tempered glass (for improved resistance to larger embers striking and breaking the glass).
The upper (domed) light in the photograph shown is plastic, and won't be able to withstand an 'A' brand exposure. To prevent entry of burning embers during a wildfire, this operable skylight should be closed.
Valleys
Many homes are constructed with roofs that contain 'valleys', the intersection where two sloping surfaces meet. These intersections can consist of metal flashing material, or in the case of asphalt composition shingles, the shingles themselves can be used. Since metal flashing can be made of aluminum, this region can be more vulnerable to wildfire exposures than the roof covering material.
Metal flashing was used on the valley of this roof. The roof covering consists of Class A asphalt composition shingles. The valley may also be 'Class A' construction, but it will depend on the underlying material(Appendix H: Roof ).
Asphalt composition shingles are 'woven' together in this valley. The valley would have the same fire rating as the rest of the roof.
Roofs: Possible Solutions
Roof Covering and Accumulation of Debris
The importance of a Class A roof covering cannot be understated. If you don't have one, you should make an upgrade to a Class A roof covering a priority item. Lack of a Class A roof covering should immediately increase your attention and focus on near home vegetation, and inspection and clearing debris from your roof and gutters. Remove debris from your roof and gutters as often as required - inspect often at first until you determine how frequently debris accumulated. You shouldn't wait for water to overflow your gutters during a heavy rain to realize that your gutters are full of debris. Care should be taken during inspection - some roofs and gutters are easier to inspect than others. Consider hiring this job out if your roof and gutters are at a high elevation, or are otherwise inaccessible.
Birdstops
If you have a clay tile roof with a barrel design, install birdstops at the end at the roof edge, and make it one of the items you look at during your inspections to make sure they are still in place.
This is an example of a properly installed bird stop at the end of a barrel-style clay tile roof.
Gutters
Gutters play a very important role on a house 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 that may lead to problems from mold and decay fungi.
Gutters: Potential Problems
Flammable debris can build up in gutters, especially from nearby or overhanging trees. Second story gutters are even more problematic, since they are seldom cleaned on an annual basis. If ignited, combustible debris in the gutter will expose the underside of the roof covering, and may be able to more easily enter the attic.
Another issue that has been seen in some houses is the use of barrel tiles to channel water from the upper gutter downspouts to the lower-story gutters, as shown below. In this case, there tends to be a buildup of debris at the transition point.
While metal gutters have been recommended over plastic ones in fire hazard areas, there doesn't appear to be any justification for this, other than the possibility that some plastics could burn. It seems advisable to avoid the unknown!
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 that happens. 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 options you have.
It is possible that your home won't have gutters. Although this will eliminate any 'debris accumulation' issue, it will result with a heavy rain load around your home, and depending on drainage, may contribute to moisture related problems.
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, and reattached when necessary.
Since second story gutters are difficult to reach, it is advisable to have these cleaned and screens added to minimize the need for subsequent cleaning. One means of doing this more economically is to organize a community-wide effort with professional help.