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.