Short answer
The Pacific Northwest is a beautiful place to own a home and a demanding one. High rainfall, mild temperatures that favor moss and biological growth, and occasional freeze events create maintenance patterns that differ from drier climates. First-year owners who establish a routine early avoid the larger, more expensive problems that deferred maintenance produces.
This guide is organized seasonally, because PNW maintenance is largely about timing your response to the climate.
Why the PNW climate changes the maintenance math
Greater Seattle's rain is concentrated in the cooler months, with mild temperatures that rarely freeze but also rarely dry exterior materials out for long periods. What this produces:
Persistent moisture. Roofs, siding, decks, fences, and crawl spaces spend much of the cool season under moisture exposure. Systems designed to manage moisture — gutters, downspouts, crawl space vapor barriers, attic ventilation — need to work properly or water finds its way in.
Biological growth. Moss, algae, lichens, and mildew grow faster in the PNW than in drier climates. Roof moss is not cosmetic — it retains moisture and damages shingles. Decks and fences without maintenance develop algae and wood degradation faster than owners from drier climates expect.
Foundation and drainage pressure. Seattle's hilly topography creates drainage situations that flat lots don't have. After heavy rain, water that isn't directed away from the foundation finds its way to crawl spaces and basements. Understanding how your lot drains is important.
Dry summers. The flip side: Seattle summers are genuinely dry, often with weeks without rain. This creates cracking and shrinkage in wood, irrigation demands, and wildfire smoke events that require HVAC filter attention.
First 30 days: foundations before anything else
Before you build a maintenance calendar, do these basics regardless of season:
Locate and label your shut-offs:
- Water main shut-off (usually at the meter near the street, and often inside near the water heater)
- Electrical panel — label every breaker if not already labeled
- Gas meter shut-off (know where it is; you'll need a wrench to operate it, which you should keep nearby)
- Individual shut-offs under sinks and at toilets
Change locks. You don't know how many keys were made for the previous owners or who has them. Rekeying is inexpensive through a locksmith; smart locks are another option.
Change smoke and CO detector batteries. Test all detectors. Replace any that are 10+ years old (check manufacture date on the back).
Change HVAC filter. Inspect it to see the condition, and start fresh. Note the size — buy several spares.
Walk the perimeter after the first rain. Observe how water moves around your home. Does it drain away from the foundation or toward it? Are gutters overflowing anywhere? Is water pooling near the house? Your first rain after purchase reveals a lot.
Fall (September–November): prepare for the wet season
Fall is the highest-priority maintenance window in the PNW, because the rainy season arrives in October and you want your systems ready before it does.
Gutters and downspouts: Clean gutters after most leaf drop is complete. In Seattle, clogged gutters overflow toward the foundation and can contribute to crawl space moisture and wood rot at the fascia. Downspout extensions should direct water away from the foundation. Check for separated sections or gaps.
Roof: Inspect from the ground or with binoculars. Look for visible moss, missing or damaged shingles, or areas where granules have washed off asphalt shingles. If moss is present, fall treatment is the standard PNW approach — two common options are iron sulfate (ferrous sulfate), which actively kills existing moss on contact, and zinc sulfate (or zinc strips installed at the ridge), which are slower-acting but provide longer-term prevention. Physical removal before applying either product is also effective. Do not pressure-wash asphalt shingles; it damages the surface.
Crawl space: Before the rainy season, check the vapor barrier condition (plastic sheeting on the ground should be intact and covering the soil), look for any standing water from summer, and confirm ventilation is unobstructed. If you have a conditioned crawl space or a dehumidifier, confirm it's operational.
Furnace/heat pump: Change the filter and schedule an HVAC service if it hasn't been done in the past year. The first time you turn on heat in October is not the time to discover the furnace needs work.
Exterior caulking and seals: Check caulk around windows, doors, and penetrations (pipes, vents). Cracked or missing caulk allows moisture into wall cavities. Re-caulk before the rains arrive.
Disconnect garden hoses from exterior spigots. Freezing temperatures are infrequent in Seattle but do occur — hoses left connected can damage the spigot and the pipe behind it.
Winter (December–February): monitor and respond
During heavy rain: Check your crawl space after significant rain events in the first year to understand whether you have any water intrusion. A small flashlight and a quick look pays off compared to discovering a wet crawl space months later.
Watch for ice on walkways and roof: Ice is infrequent but dangerous when it occurs. Have sand or ice melt accessible before the first freeze event.
HVAC filter: Change it if you haven't in the past 3 months.
Chimney/fireplace: If you have a wood-burning fireplace, have the chimney inspected and cleaned annually by a licensed chimney sweep before heavy use. Creosote buildup is a fire hazard.
Space under the house: If your home has any pipes in an unheated space (older crawl spaces, exposed exterior walls), know whether they need protection during freeze events.
Spring (March–May): repair and prepare
Gutters again: Clean gutters in spring to remove winter debris, particularly in areas with conifers. Inspect for damage from heavy rain or ice events.
Roof inspection: Walk the perimeter and look for any changes from fall — new moss growth, debris accumulation in valleys, or visible damage. Hire a professional roof inspector if you have any questions about condition.
Crawl space inspection: Once the rainy season is winding down, inspect the crawl space for any moisture damage, mold, or pest activity from the wet season.
Deck and exterior wood: Inspect for wood rot, loose boards, and finish degradation. The PNW wet season accelerates deck aging. Cleaning and applying a deck sealant or stain in late spring (when it's dry enough to cure properly) extends deck life significantly.
Exterior paint: Check painted surfaces for peeling, especially on north-facing walls and around windows. Peeling paint is a moisture management problem as much as an aesthetic one — exposed wood absorbs water and leads to rot.
Irrigation: If you have an in-ground irrigation system, this is when to restart it and check for broken heads or leaks after the wet season. Deep root watering in summer is better for trees and shrubs than frequent shallow watering.
Summer (June–August): dry-season tasks
Summer is the best window for larger exterior projects because it's dry enough for materials to cure properly.
Deck sealing and staining: Best done in dry weather with temperatures above 50°F and no rain forecast for 24–48 hours. Check product instructions for specific requirements.
Exterior painting: If repainting is needed, summer is the window. Painting in rain or cold temperatures causes adhesion failure.
Tree and shrub maintenance: Prune trees that overhang the roof or are close to the house. Overhanging branches accelerate moss and debris accumulation on roofs.
Air quality: Wildfire smoke from eastern Washington and other western states has become a regular summer consideration. Check HEPA filter condition on air purifiers. A high-quality MERV-13 HVAC filter helps, though not all HVAC systems can handle the restriction of very high MERV ratings — check your equipment's specifications.
Irrigation monitoring: Water restrictions and drought conditions are increasingly common in Washington summers. Know your local water utility's current status.
Ongoing throughout the year
HVAC filter: Every 1–3 months depending on filter type and household (more frequent with pets or dust). Keep spares.
Water heater: Know your water heater age, watch for leaks or corrosion, and ask a plumber whether anode rod inspection or replacement makes sense for your model. Manufacturer guidance and water chemistry affect the interval.
Smoke and CO detector tests: Monthly test (most detectors have a test button); annual battery change.
Pest inspection: Greater Seattle has carpenter ants as a significant pest concern (they thrive in moist wood). An annual pest inspection is a reasonable investment, particularly for homes with wood-to-soil contact or any moisture history.
Building your maintenance budget
Percentage-of-home-value rules are only a starting point. In the PNW, budget more conservatively if:
- The home is older than 20 years
- The roof is older or already shows moss, granule loss, lifted shingles, or flashing concerns
- You have a large deck or significant exterior wood
- The home had deferred maintenance visible in the inspection
Keep a maintenance log from year one. Note what you do and when. This history is useful for future reference and is meaningful information when you eventually sell.