Fast, Reliable Duct Repair & Sealing Across Seattle
Duct repair and sealing in Seattle typically costs $280–$750 depending on accessibility and damage extent, with most jobs completed in a single visit. We’re usually on-site in Seattle neighborhoods within 24–48 hours of your call.
We’ve spent 11 years working inside Seattle’s homes — from the pier-and-beam crawl spaces of Ballard’s 1920s craftsman bungalows to the hillside ranches of Queen Anne with their tight attic duct runs. Our Duct Repair & Sealing team knows the local housing stock: where the flex duct sags, where the coastal moisture corrodes metal joints first, and where old gravity-furnace plenums hide sealed up inside walls and crawl spaces. Richard Anderson, our owner and lead technician, personally oversees every Seattle job. If your ducts are leaking heated air into a damp crawl space or pulling musty air into your living room, call us at (877) 335-1974 for a free estimate.
Why Landmark Air Duct Cleaning Service Washington Is Seattle’s Preferred Duct Repair & Sealing Company
Our reputation in Seattle is built on 732 verified customer reviews averaging 4.9 stars — a volume that reflects hundreds of real homes across Capitol Hill, Wallingford, West Seattle, and beyond. Seattle homeowners research before they call, and they stick with us because the same person who answers the phone (Richard Anderson) runs the equipment on-site. There’s no rotating crew, no subcontractor handoff.
We respond to Seattle calls within 24–48 hours, and we carry the local knowledge that speeds diagnosis: we know which Wallingford blocks have the original 1930s duct retrofits, which Ballard crawl spaces stay wet year-round from marine humidity, and how the late-summer wildfire smoke season drives post-August duct inspections. That specificity saves you time and money on every job.
Our Duct Repair & Sealing Services in Seattle
Duct Sealing with Mastic Sealant
Seattle’s persistent coastal humidity — especially in homes near Puget Sound — corrodes metal duct joints years faster than drier inland climates. We apply professional-grade mastic sealant to every joint and seam, creating a flexible, permanent bond that outlasts foil tape alone. In homes from Magnolia to Madrona, we’ve found that mastic-sealed systems hold their pressure tests through multiple rainy seasons while tape-only repairs fail within 18 months. A typical mastic sealing job for a Seattle single-family home runs $280–$450.
Flex Duct Repair
Flex duct was the go-to solution for retrofitting forced-air systems into Seattle’s early-20th-century homes, but those tight crawl spaces under craftsman bungalows create perfect conditions for sagging, crushing, and tearing. We replace damaged flex runs with properly supported, insulated sections rated for Seattle’s moisture exposure. In Ballard and Wallingford especially, we regularly find original flex duct from 1980s–1990s retrofits that has collapsed or pulled loose at the collar connections. Flex duct repair in Seattle typically ranges from $180–$340 per run, with full replacement of a compromised system running higher.
Metal Duct Repair
Galvanized metal ductwork in Seattle’s coastal environment develops pinhole corrosion and joint separation that inland technicians rarely see. We cut out corroded sections, fabricate replacements on-site, and seal with mastic plus mechanical fasteners — never tape alone on metal. Homes in neighborhoods like Alki Beach and West Seattle’s shoreline blocks see this corrosion accelerated by salt-laden air. Metal duct repair in Seattle generally runs $320–$580 depending on access and extent.
Duct Insulation
Uninsulated or degraded duct insulation in Seattle’s damp crawl spaces creates condensation on cold duct surfaces — a direct path to mold colonization inside your airflow. We install R-8 insulated wrap on exposed duct runs, with vapor-barrier outer layers designed for marine climates. This is especially critical in Seattle’s 1910s–1940s housing stock, where retrofitted ducts were often left bare in crawl spaces that stay humid 8–9 months of the year. Duct insulation in Seattle typically costs $350–$650 for a standard residential system.
What happens when you call
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A real person answersNo phone trees — you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in Seattle
We run professional-grade Rotobrush and Nikro cleaning and inspection systems — the same equipment brands used by commercial restoration contractors — and we stock mastic sealants, foil tapes, and insulation materials sized for Seattle’s common duct configurations. For air quality upgrades following repair and sealing, we work with Honeywell, Aprilaire, and Abatement Technologies filtration and sanitizing products. Having the right materials on the truck means we don’t waste your time with supply runs across town.
Common Duct Repair & Sealing Problems We See in Seattle Homes
- Flex duct sags and leaks in tight crawl spaces. Seattle’s retrofitted craftsman bungalows force duct runs through cramped, irregular cavities where flex duct loses support, sags below the blower’s airflow threshold, and develops leaks at the collars. The humid crawl-space air then infiltrates the system, carrying mold spores and musty odors into living spaces.
- Metal duct joints corrode from persistent coastal moisture. Homes within a few miles of Puget Sound — Magnolia, Alki, parts of West Seattle — show accelerated galvanic corrosion at sheet-metal joints. The telltale sign is rust staining on duct exteriors and reduced airflow at distant registers.
- Abandoned gravity-furnace plenums create hidden dead-air chambers. In Ballard, Wallingford, Queen Anne, and Capitol Hill, we regularly discover that the original gravity-furnace plenum box was never removed when forced-air was retrofitted. These sealed chambers contain decades of biological debris and leak moist, stagnant air into new ductwork through shared wall cavities.
- Wildfire smoke deposits drive post-season inspection demand. Since 2017, Eastern Washington and Oregon wildfire smoke drifting into Seattle each August–September has created a predictable annual spike in duct contamination. Fine particulate matter infiltrates through leaks and accumulates in duct interiors, degrading air quality through the heating season.
Pricing for Duct Repair & Sealing in Seattle, WA
Here’s what duct repair and sealing costs in Seattle’s current market:
| Service | Typical Range in Seattle |
|---|---|
| Mastic sealant application (full system) | $280–$450 |
| Flex duct repair (per run) | $180–$340 |
| Metal duct repair (section replacement) | $320–$580 |
| Duct insulation (R-8 wrap, standard home) | $350–$650 |
| Gravity-furnace plenum removal + sealing | $450–$750 |
Three factors push Seattle jobs toward the higher end: crawl-space accessibility (pier-and-beam homes common to Ballard and Wallingford are tighter than full basements), extent of moisture damage requiring material replacement versus sealing only, and whether we need to remove abandoned plenum structures. We provide upfront, itemized estimates before any work begins — call (877) 335-1974 to schedule your free assessment.
We Also Serve Cities Near Seattle
Our service radius extends to White Center, Mercer Island, Bellevue, and Boulevard Park — all within regular travel range for our Seattle-based team. Richard Anderson handles routing personally, so you’re not waiting on a dispatcher guessing at drive times from a call center outside the area.
Serving Seattle, WA — Our Local Coverage Area
We’re based in the Seattle area and know this community well. Use the map below to see our service coverage — if you’re nearby, we can almost certainly help.
FAQs — Duct Repair & Sealing in Seattle
Mastic sealant in Seattle’s marine climate typically lasts 10–15 years, but tape-only repairs often fail within 18–24 months due to moisture cycling. We always apply mastic as the primary seal, with foil tape as backup reinforcement, specifically because Seattle’s October–May rainy season keeps crawl spaces humid enough to degrade lesser materials. For a system inspection and proper sealing estimate, call us at (877) 335-1974.
Yes — we remove abandoned gravity-furnace plenums as part of our standard repair protocol when we find them. We recently sealed the flex-duct runs in a Ballard craftsman where the original gravity-furnace plenum had been left sealed inside the crawl space. That dead-air chamber was leaking moist air into the new ductwork, causing mold growth. We removed the old plenum, applied mastic sealant to all joints, and insulated the exposed ducts with R-8 wrap, restoring proper airflow and eliminating the moisture problem. If you suspect a hidden plenum in your home, call (877) 335-1974 for an inspection.
Sealing alone won’t remove existing smoke deposits, but it prevents re-infiltration and is essential after cleaning. We typically pair duct sealing with Rotobrush mechanical cleaning following wildfire smoke events, then seal all joints to block future particulate entry. Seattle’s August–September smoke season has made this combined service increasingly common since 2017. Call (877) 335-1974 to schedule post-smoke cleaning and sealing before your heating season starts.
Flex duct repair addresses the sagging, torn, or disconnected flexible tubing common to Seattle’s 1980s–1990s forced-air retrofits in craftsman homes — we replace runs and improve support. Metal duct repair fixes corroded or separated rigid galvanized sections, more often found in later additions or basement systems. Flex work is generally faster and less expensive; metal repair requires fabrication and more labor. Richard Anderson assesses which approach your system needs during the free estimate. Call (877) 335-1974 to book.
We use Rotobrush brush-and-vac systems for pre-repair cleaning and inspection, then apply mastic sealant by hand for the sealing phase — the right tool for each step. Our Nikro and Rotobrush equipment lets us visually verify duct interior condition before we seal, so we’re not trapping debris behind a permanent seal. For Seattle’s older, debris-heavy systems, this inspection-first approach is critical. Call (877) 335-1974 to see how we handle your specific duct configuration.
Ready to fix your Seattle home’s duct leaks? Call Landmark Air Duct Cleaning Service Washington at (877) 335-1974 for your free estimate. Richard Anderson, our owner and lead technician, will assess your system personally — whether you’re dealing with corroded metal joints in a Magnolia crawl space, sagging flex duct in a Wallingford bungalow, or a mystery odor that might be a hidden gravity-furnace plenum. We serve Seattle, White Center, Mercer Island, Bellevue, and Boulevard Park with 11 years of specialist focus and 732 customer reviews behind every job.
Written by Richard Anderson, Owner and Lead Technician at Landmark Air Duct Cleaning Service Washington, serving Seattle since 2013.