Mature conifers are characteristic of Western Washington and they interact with a house in more ways than most homeowners register.
What trees do to a house
Shade the roof. A shaded roof dries slowly after rain, which is precisely the condition moss needs. Two identical houses a few streets apart can be a decade apart in roof life because of canopy.
Drop debris. Needles fill gutters and valleys year-round rather than in one autumn burst, holding moisture against roofing and creating a bed for growth.
Intrude into drains. Roots seek water, and a slightly leaking sewer lateral offers exactly that. In older neighbourhoods with mature street trees, root intrusion is routine.
Fall. The largest single source of serious windstorm damage in Washington.
What routine work covers
Trimming limbs overhanging the roof increases sunlight and airflow and reduces debris. That is genuinely valuable maintenance and it does more for roof life over time than any moss treatment.
Clearing accumulated debris from the roof and gutters. Removing obviously dead limbs within reach.
When you need an assessment
The important point is that a tree can be seriously compromised without looking it. Internal decay, root problems and structural defects are frequently invisible from the ground to an untrained eye.
Warrant an assessment for: any large tree within falling distance of the house, particularly before storm season. Trees showing dead limbs in the canopy, thinning foliage, or fungal growth at the base or on the trunk. Any noticeable lean, especially a new or increasing one. Trees with visible trunk damage or cavities. Any tree where nearby excavation has cut roots.
A qualified arborist assesses structural condition rather than just appearance, which is the difference between an opinion and an assessment.
Before storm season
Washington windstorms arrive in the wetter months and bring down trees every year. Assessing before the season rather than after is the whole point — a tree identified as a risk in September can be dealt with; one identified in December has already fallen.
Regulations
Tree removal is regulated in many Washington jurisdictions, particularly for larger trees, trees in critical areas, and in cities with tree protection provisions. Seattle among others has requirements affecting what may be removed.
Confirm the position before removing anything substantial. Retrospective consequences for unauthorised removal are a real possibility, and they are avoidable with a phone call.
Choosing who does the work
Tree work near a house is genuinely hazardous — falls, equipment, and the potential to drop something large onto a roof.
Verify registration, bond and insurance as with any contractor. Ask specifically about insurance covering damage to property, since the exposure here is unusually direct. Ask how they will protect the roof and structures during removal.
Be cautious of door-to-door tree services after storms, which is the same pattern seen with storm-chasing roofers.
Planting
For anything new, consider the mature size rather than the size at purchase, and keep it away from the sewer lateral route and far enough from the house that its eventual canopy will not sit over the roof. A tree planted thoughtfully is an asset; one planted too close becomes a recurring cost.