Fast, Reliable Duct Repair & Sealing Across San Lorenzo
Duct repair and sealing in San Lorenzo typically costs $180-$650 depending on whether you’re sealing accessible joints or replacing corroded metal runs, and most jobs are completed in a single visit. If your home was built in the Bohannon tracts between 1944 and 1955, your ductwork is likely aging in near-lockstep with every house on your block. That’s not a coincidence. It’s the defining reality of San Lorenzo’s housing stock, and it’s why we’ve spent decades working specifically on the raised-foundation crawl spaces that dominate the 94580 ZIP.
We’re Bellows Air Duct & Vent Co., founded in 1984 and named for the oldest air-moving tool there is. Our Duct Repair & Sealing crew knows San Lorenzo’s homes the way a mechanic knows an engine. We don’t guess. We camera-inspect every system before we quote a price, and we show you what we see. Call (844) 685-6342 for a free estimate. We’ll be there when we say.
Why Bellows Air Duct & Vent Co. Is San Lorenzo’s Preferred Duct Repair & Sealing Company
We’ve been serving San Lorenzo and the broader East Bay for over 42 years. In that time, we’ve repaired ductwork in the Bohannon tracts off Grant Avenue, along Hesperian Boulevard, and throughout the neighborhoods near San Lorenzo Creek. The patterns repeat. The moisture damage at the boot connections. The rodent-chewed flex sections. The failed tape seals that someone applied three summers ago. We know what to look for because we’ve seen it hundreds of times.
Our technicians are background-checked and uniformed, and they answer to a live person at our office 24 hours a day. Not a voicemail. Not an app. When you call (844) 685-6342, someone picks up. That’s been our practice since 1984.
Every job carries our 90-Day Done Right Promise in writing. If it’s not right, we make it right. No paperwork, no arguing. We stand behind it because we always have.
We also offer a standing $50 off any repair over $250, a free second opinion on any written estimate, and a permanent 5% senior and veteran discount. The price we quote is the price on the invoice. No bait coupons, no changes at the door.
Our Duct Repair & Sealing Services in San Lorenzo
Duct Sealing
San Lorenzo’s damp crawl spaces destroy tape seals faster than drier inland cities. We use professional-grade mastic sealant applied after Rotobrush cleaning of the joint surfaces, so the seal actually bonds instead of peeling away in the humidity. For Bohannon tract homes with original sheet metal runs, we seal the surviving joints and boots, then pressure-test to verify. A typical duct sealing job in San Lorenzo runs $180-$340 for partial-system work and $380-$550 for full-system sealing.
Metal Duct Repair
Original 1950s galvanized sheet metal in San Lorenzo’s crawl spaces doesn’t fail uniformly. It corrodes at the boots, at the elbows, and anywhere the original installer left a gap that collected condensation. In the Bohannon tracts off Grant Avenue, we repaired a 1948 minimal traditional’s metal duct runs where decades of crawl-space moisture had corroded through the galvanized sheet metal at the boot connections. Our crew sealed the surviving runs with Rotobrush-cleaned mastic and replaced the rotted flex sections with insulated flex duct, restoring airflow without a full re-duct. Metal duct repair in San Lorenzo typically runs $280-$480 for localized patching and $520-$850 for extensive section replacement.
Flex Duct Repair
The flex-duct connection points in San Lorenzo’s original tract homes were never designed to resist decades of rodent pressure. Local technicians consistently find rodent harborage and nesting debris inside the crawl-space duct runs of the Bohannon homes. The original tract design left flex-duct connection points and gaps that generations of rats and mice have exploited, a pattern that repeats block after block across San Lorenzo in a way that is far less uniform in surrounding cities with more varied housing stock. We remove contaminated flex, seal the entry points with rodent-resistant materials, and install new insulated flex with secure mechanical connections. Flex duct repair in San Lorenzo typically runs $220-$420 per run.
Duct Insulation
Unconditioned crawl spaces in San Lorenzo stay cool and damp year-round from bay influence. Bare or degraded duct insulation wastes energy and promotes condensation that accelerates metal corrosion. We install new foil-faced insulation with proper vapor barriers, sized for the damp environment these homes sit in. Duct insulation in San Lorenzo typically runs $340-$580 for partial replacement and $680-$950 for full-system re-insulation.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in San Lorenzo
We specify professional-grade equipment and materials from Nikro, Honeywell, and Aprilaire, the same brands serious HVAC contractors use. For San Lorenzo’s moisture-challenged crawl spaces, we stock mastic compounds and insulated flex duct rated for damp-location installation, so we’re not ordering parts and making you wait. Most repairs are completed in a single visit because our trucks carry what these homes actually need.
Common Duct Repair & Sealing Problems We See in San Lorenzo Homes
- Original sheet metal ducts perforated by sustained crawl-space moisture. San Lorenzo’s position adjacent to the bay and San Lorenzo Creek keeps crawl spaces persistently damp from marine layer humidity year-round, unlike drier inland East Bay cities such as Livermore or Dublin. This sustained moisture environment means duct contamination in these homes skews heavily toward mold and mildew growth rather than just dust accumulation. The galvanized coating on 1950s metal eventually succumbs, and we find pinholes and boot corrosion that simply don’t occur at the same rate in drier climates.
- Flex-duct connection gaps exploited by generations of rodents. The original tract construction left connection points that rats and mice have refined into highways over seventy years. We regularly pull nests and debris from runs that have been partially blocked for years, cutting airflow to back bedrooms.
- Mastic and tape seals failing rapidly due to persistent dampness. Standard duct tape degrades in San Lorenzo’s humidity within two to three years. We see homes where homeowners or prior contractors re-taped joints repeatedly, each time watching the adhesive turn to goo. Proper mastic application after surface prep lasts substantially longer, but even mastic needs periodic inspection in this environment.
- Insulation breakdown exposing bare metal to condensation. Original fiberglass insulation in these crawl spaces has often compressed, torn, or absorbed moisture until it no longer protects the duct. Bare metal sweats in humid conditions, accelerating the corrosion cycle.
Pricing for Duct Repair & Sealing in San Lorenzo, CA
Here’s what duct repair and sealing costs in San Lorenzo’s market:
| Service | Typical Range |
|---|---|
| Duct sealing (partial system) | $180 - $340 |
| Duct sealing (full system) | $380 - $550 |
| Metal duct repair (localized) | $280 - $480 |
| Metal duct repair (extensive) | $520 - $850 |
| Flex duct repair (per run) | $220 - $420 |
| Duct insulation (partial) | $340 - $580 |
| Duct insulation (full system) | $680 - $950 |
What moves the price: accessibility of the crawl space, extent of corrosion or rodent damage, whether we can salvage original metal or must replace sections, and how many runs need attention. We camera-inspect before we quote, so you see what we see. Estimates are free. Call (844) 685-6342.
Don’t forget our standing offers: $50 off any repair over $250, free second opinion on any written estimate, and permanent 5% senior and veteran discount.
We Also Serve Cities Near San Lorenzo
Our technicians work throughout the East Bay. We regularly handle Duct Repair & Sealing in San Lorenzo and neighboring communities including San Leandro, Castro Valley, Hayward, and Union City. Each city has its own housing patterns and duct configurations, but the same Bellows standard applies: camera inspection, upfront pricing, and our 90-Day Done Right Promise.
Serving San Lorenzo, CA - Our Local Coverage Area
We’re based in the San Lorenzo 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 San Lorenzo
They were built at the same time, with the same materials, in the same damp crawl-space environment. San Lorenzo’s nearly identical 1944-1955 Bohannon tract homes share a compressed duct-aging timeline, so the entire 94580 ZIP faces simultaneous crawl-space duct failure, a pattern absent in nearby cities with varied housing vintages. When your 1952 ranch was constructed, so was the identical house three doors down, and both have endured seventy years of marine-layer humidity. Call (844) 685-6342 for an inspection - estimates are free.
Often they can be saved if the corrosion is localized to boots and connection points. We camera-inspect to determine whether patching and sealing is viable or if sections have perforated beyond repair. In many San Lorenzo homes, we restore airflow by repairing the worst sections and sealing the rest, avoiding the cost of full re-ducting. Metal duct repair in San Lorenzo typically runs $280-$850 versus $2,500-$5,000+ for complete replacement. Call (844) 685-6342 and we’ll show you exactly what your system needs.
Sealing alone won’t eliminate odor if nesting debris remains inside. We remove contaminated material, sanitize the runs with Nikro equipment, seal entry points with rodent-resistant materials, then apply mastic to joints. The smell persists until the source is gone. If you’re noticing odor in your San Lorenzo home, call (844) 685-6342 - we’ll camera-inspect and give you a straight answer on whether sealing solves it or if removal and replacement is needed.
Localized metal duct repair in San Lorenzo runs $280-$480, extensive section replacement runs $520-$850, and full system replacement typically starts at $2,500 and can exceed $5,000 depending on home size and crawl-space accessibility. The Bohannon tracts’ compact footprints often keep replacement costs lower than larger homes, but the tight crawl spaces can add labor time. We always explore repair first and show you camera evidence before recommending replacement. Call (844) 685-6342 for a free estimate.
Yes. Mastic sealant properly applied after surface cleaning outlasts duct tape by years in humid conditions. Tape adhesive breaks down in San Lorenzo’s persistent crawl-space moisture, which is why we see so many homes with peeling, failed tape jobs. Our mastic application follows Rotobrush cleaning of the joint surfaces for actual bonding, not just surface contact. Mastic sealing in San Lorenzo typically runs $180-$550 depending on system size. Call (844) 685-6342 to schedule.
Ready to fix your ductwork? Call Bellows Air Duct & Vent Co. at (844) 685-6342 for a free estimate in San Lorenzo. We’ll camera-inspect your system, show you exactly what’s failing, and give you one honest price before we start. No bait coupons, no changes at the door. Done right - and backed in writing for 90 days.
Written by Ray Castillo, Owner at Bellows Air Duct & Vent Co., serving San Lorenzo since 1984.