In Bellevue, roof care is mostly about moisture: keeping the attic dry from below and keeping moss, needles and standing water off the roof from above. Here is what matters and why.
Why does roof ventilation matter?
Roof ventilation matters because it carries moist air out of the attic before it condenses on cold wood. In a Northwest winter the air outside is damp and the roof deck is cold for months. Without steady airflow from soffit vents up to ridge or roof vents, the sheathing gets wet, mold grows and the roof ages from the underside. The residential code calls for vent openings equal to 1/150 of the attic area, with some exceptions. A re-roof is the best time to fix poor ventilation.
What causes ice dams, and do they happen here?
Ice dams are rare in Bellevue. They form when snow sits on a roof for days in freezing weather, heat leaking from the house melts it from below, and the water refreezes at the cold eaves. That takes a long stretch of snow cover and cold, which the lowlands seldom get. Snow here usually melts within days. They can show up in an unusual cold snap, most often on homes with thin attic insulation. Good insulation and ventilation prevent them.
Why is there moss, algae or black streaks on my roof?
Moss grows on roofs here because they stay damp and shaded for months. Tall firs and cedars block the sun and drop needles that hold water against the shingles. North-facing slopes get it worst. Black streaks are a different thing: an algae that feeds on the filler in asphalt shingles. Algae is mostly a cosmetic problem. Moss is not. Its roots lift shingle edges, hold water against the roof and let rain blow underneath.
Should I clean or pressure wash my roof?
Clean it, but do not pressure wash an asphalt shingle roof. High-pressure water blasts off the granules that protect the shingle, can force water up under the laps and can shorten the roof's life by years. Shingle makers warn against it. The safer way is to loosen thick moss gently with a soft brush, working down the slope, then apply a moss treatment made for roofs and let the rain rinse the dead moss away over the following weeks.
Follow the product label and keep run-off out of storm drains, which lead to local streams and lakes. Zinc strips near the ridge and trimming branches back from the roof slow regrowth. HomeGuide lists roof cleaning at $250 to $600 nationally.
Do I need new gutters with a new roof?
You need new gutters with a new roof only if the old ones are worn out, undersized or damaged. Gutters that are sound can stay. A re-roof is a convenient time to replace them, because the fascia is exposed, any rot can be fixed and new drip edge can be set to drain into them properly. We tell you which case yours is.
Do gutter guards work?
Gutter guards work partly. They keep out leaves and large debris and cut down how often gutters need cleaning. Fir and cedar needles are the hard case. They are fine enough to slip through many screens or mat on top of them, so no guard is maintenance-free under evergreens. Fine-mesh guards do best. Nationally, guards cost $15 to $45 per linear foot installed.
How does local weather wear out a roof?
Rain and shade do most of the wear here. Long wet months keep shingles damp, moss follows, and constant moisture ages flashing, sealants and wood. Wind storms in fall and winter break the seal on older shingles and bring down limbs. Summer sun dries out the asphalt on south and west slopes. Hail is rare, and snow is occasional and short-lived, so neither does much harm in a normal year.
Why is there frost or condensation in my attic?
Condensation in the attic comes from warm, moist air leaking up from the house and meeting the cold underside of the roof. Showers, cooking and laundry all add moisture. The common faults are bath or kitchen fans that vent into the attic instead of outdoors, gaps around ceiling lights and hatches, and soffit vents buried under insulation. On a cold clear night it can freeze as frost and then drip when it thaws, which looks just like a roof leak.
How often should a roof be inspected?
Once a year is a good rule in Bellevue, ideally in early fall before the rains. Add a check after any major wind storm or if a limb hits the roof. Homes under heavy tree cover do well with a second visit in spring to clear needles and look for moss. Flat roofs should be checked twice a year. Cleaning follows the same rhythm. Most roofs under trees here need needles and debris blown off once or twice a year, and a moss treatment every year or two, before the growth gets thick enough to lift shingle edges.
How often should gutters be cleaned here?
At least twice a year: in late fall once the leaves are down, and in spring. Homes under firs and cedars may need three or four cleanings, since needles fall all year. HomeGuide lists gutter cleaning at $100 to $250 nationally.
How do I know if my attic has enough ventilation?
Your attic has enough ventilation if it stays dry through the winter. Go up on a cold morning with a flashlight. Good signs are clean, dry sheathing and daylight at the soffit vents. Bad signs are dark staining or mold on the wood, rusty nail tips, damp insulation and a musty smell. The code figure is vent area equal to 1/150 of the attic floor, split between low and high vents. A roofer can measure what you have.
Do I need ridge vents or soffit vents with a new roof?
You need both an intake and an exhaust, and a new roof is the time to get them right. Soffit vents let air in at the eaves. Ridge vents or roof vents let it out at the top. One without the other does little. Many older Bellevue homes have soffits blocked by insulation or paint. HomeGuide lists a ridge vent at $350 to $600 installed nationally.
Do powered attic fans help?
Powered attic fans help less than people expect. Their main use is pushing out summer heat, and Bellevue summers are mild. The problem here is winter moisture, which steady passive airflow from soffit to ridge handles better. A powered fan in an attic with too little intake can pull warm, damp air up from the house and make condensation worse. Fix the intake and exhaust vents first.
Why is there mold on the underside of my roof deck in the attic?
Mold on the underside of the roof deck nearly always comes from condensation, not from a roof leak. Warm, moist house air reaches the cold sheathing and wets it night after night through the long damp season. Look for a bath or dryer fan that vents into the attic, blocked soffit vents and gaps around the attic hatch. It often shows up after a cedar shake roof was replaced with shingles on solid plywood and no vents were added. Fix the moisture source first, then have the mold treated.
Do zinc strips stop moss?
Zinc strips slow moss down but do not stop it everywhere. Rain washes a little zinc off the strip and down the roof, which discourages growth for some feet below it. The effect fades lower down the slope and under heavy shade, and strips do not kill thick moss that is already there. They work best on a clean roof, fitted just under the ridge, along with algae-resistant shingles and branches cut back.
What moss treatment is safe for the garden below?
No moss killer is harmless to plants, so the safe approach is in how it is used. Pick a product labelled for roofs and follow the label exactly. Apply it in calm, dry weather so it does not drift. Wet the plants below with clean water first, cover the tender ones and rinse them afterward. Disconnect downspouts from rain barrels for a while. Keep run-off out of storm drains. We name no product here, because labels and formulas change.
How do I keep needles and debris from building up in the roof valleys?
You keep valleys clear by removing needles before they mat down, because no product stops them falling. A valley full of fir and cedar needles acts like a sponge and a dam. It keeps the shingles wet, feeds moss and pushes rain sideways under the roofing. Have valleys, the uphill side of chimneys and skylights and the gutters blown or brushed clean in late fall and again in spring. Cutting branches back from the roof reduces the load.
A free roof inspection with photos and a written quote is the only way to get a real price for your roof. Call or text The Bellevue Roofers at (425) 522-5354.