Roofs, Gutters and Valleys: Clearing Needles for Wildfire

Why is the roof the most vulnerable part of a house?

Montana DNRC's landowner guide for west-central Montana says it plainly: the roof is the most vulnerable part of a home. The University of Nevada, Reno Extension's Wildfire Home Retrofit Guide states that 60 to 90 percent of home loss in wildfires is due to embers, which can ignite materials directly or ignite something next to the house that then exposes it to flames and heat.

A clean roof with a fire-rated covering gives embers very little to work with. A roof with needles in the valleys and leaves in the gutters gives them a fuel bed sitting against wood. Our guide to how homes actually catch fire covers the ember science in depth.

Where do needles and embers collect on a roof?

In the same places, which is the point. The UNR guide explains that wind-blown embers gather where vegetative debris has accumulated, and names the places where the roof meets another material: roof-to-wall intersections on split-level homes, dormers, and the area around a chimney chase. Building materials usually change at those edges, and the adjacent material may not be as fire resistant as the roofing.

Add roof valleys, where two slopes meet and funnel needles downhill, the flat area behind a chimney, the space around skylights, especially flat skylights on low-slope roofs, and of course the gutters. If you walk around the house after a windy day in October, you will see the pattern: needles pile in valleys and against every upslope wall.

Why are gutters such a problem?

Because of what they are attached to. The UNR guide notes that debris in a gutter can ignite from embers, and the flames can then ignite other parts of the roof edge, specifically the wood-based roof sheathing and the fascia board. A gutter is essentially a trough of dry fuel bolted to the most vulnerable joint on the house.

The guide's fixes are practical: remove vegetative debris from gutters on a regular basis during fire season, install a noncombustible, corrosion-resistant metal drip edge to protect the sheathing and fascia at the roof edge, and consider a noncombustible gutter cover.

Do gutter guards solve the problem?

They help, but they do not end the job. The UNR guide recommends a noncombustible gutter cover to minimize debris in the gutter, and then adds a caution: some gutter covers cause debris to accumulate on the roof behind the gutter, so they still need routine maintenance. A guard that keeps the trough clean but builds a berm of needles along the roof edge has moved the fuel, not removed it.

If you add guards, choose noncombustible ones and keep checking the roof edge above them. Plastic or foam inserts are not what the guide describes.

How often do roofs and gutters need clearing in Montana?

More than once a year under conifers. DNRC's guide tells owners to regularly clean the roof and gutters. The Colorado State Forest Service's home ignition zone guide puts clearing pine needles and other debris from the roof, deck and gutters on its list of tasks to address as needed, more than once a year.

In the Missoula and Bitterroot valleys, a sensible rhythm for a house under pines is a spring clearing after melt, checks through fire season after windy stretches, and a fall clearing once the leaves and the autumn needle fall are down. Our spring checklist and fall cleanup checklist include it, and the maintenance schedule puts it in the year.

Should branches over the roof be removed?

Yes. DNRC's guide says to remove branches overhanging or touching the roof to a distance of at least 10 feet. The Colorado State Forest Service guide also calls for pruning branches that hang over the roof and removing all fuels within 10 feet of the chimney.

Overhanging limbs drop needles straight into the gutters and can bring burning material to the roof. Removing them is tree work, often over a roof, and it should be done with ropes and rigging rather than letting limbs fall on shingles. That is part of our tree services and our fire mitigation work.

What about the chimney and stovepipe?

The UNR guide treats chimneys as another roof-to-wall connection where debris and embers gather, and recommends metal step flashing where the roof meets the chimney chase. It also recommends covering chimney and stovepipe outlets with a noncombustible metal screen with openings no smaller than 3/8 inch and no larger than 1/2 inch, to reduce embers leaving the chimney, and closing the fireplace flue in fire season when it is not in use.

Chimney screens, flashing and cleaning are jobs for a chimney sweep or roofer. Keeping fuel and branches back from the chimney is the yard side, and that we do.

Does the roof covering itself matter?

A great deal. The UNR guide explains that roof coverings carry Class A, B or C fire ratings, with Class A giving the most protection, and that untreated wood shake or shingle roofs are unrated and not desirable. It lists asphalt fiberglass composition shingles, clay and cement tiles and some metal roofing as Class A materials, and notes that some Class B or C coverings reach a Class A rating by assembly with added layers. DNRC's guide says roofs of composite shingles, metal or tile are fire ignition resistant.

We do not do roofing. If your roof is wood shake, or you are not sure what rating it carries, talk to a licensed roofer. What we can do is keep whatever roof you have clean, and keep trees from loading it with needles.

Does a fire-rated roof still need clearing?

Yes. A Class A rating describes the roof covering, and the UNR guide points out that the rating does not cover the places where the roof meets other materials at its edges. Those edges, valleys and wall joints are where needles pile up, and needles burn the same on metal as on shingles. The guide's advice for every roof type includes removing accumulated vegetative debris on a regular basis.

Low-slope roofs and flat skylights hold debris longer, according to the UNR guide, and glass skylights on steeper roofs face more radiant heat from anything burning nearby. Whatever the roof, look behind chimneys, in valleys and along upslope walls every time you clear the gutters.

Is it safe to clean your own roof?

Many owners do it, but it is ladder and roof work, and a fall is a serious risk. Work on a dry, calm day, use a stable ladder that extends past the roof edge, never work alone, and do not walk steep, wet, frosty or mossy roofs. A blower on a roof can throw you off balance, so keep both hands free when you can. A roof rake from the ground handles some low-slope edges.

If you would rather not, roof and gutter needle clearing is part of the near-structure cleanup in our fire mitigation service, and can be added to leaf removal or a seasonal cleanup.

What should you check after you clear the roof?

Look at the vents while you are up there or on the ladder. DNRC says all vent openings should be covered with 1/8-inch corrosion-resistant metal mesh, and the UNR guide says torn screens and quarter-inch mesh should be replaced. Debris packed against a vent screen can itself become a source of embers, according to the same guide. Our post on vents, screens and eaves covers this.

Then look down. The needles you just pulled off the roof land in the five feet next to the house, where IBHS says removing all combustibles is the most effective defensible space action an owner can take. Rake them up and take them away rather than leaving them at the foundation; our pine needle cleanup guide has options.

Where this fits

Roof and gutter clearing is the top of the home ignition zone, and it is part of our Montana Wildfire Guide. The next layers down are zone 0, the first five feet and the defensible space zones beyond it. Call HJ Property Care & Tree Service at (406) 215-7319 or request a free estimate and we will walk the property with you.

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