Duct Repair
Duct repair fixes the ducts you already have: a run that has slipped off its collar, flex duct crushed flat behind a soffit, a rusted section under a leaking humidifier, a joint that rattles every time the blower starts. Most repairs involve one run or one joint and finish in a single visit, and the $90–$150 diagnostic visit is folded into the repair if you proceed. When the damage is spread across the whole system, or the room never worked from the day the house was built, the fix is new ductwork and we say so.
Start with the pattern, because it tells us where to look. One dead room in a house that is otherwise comfortable is almost never the furnace: it is a branch run that has slipped off its take-off at the trunk, a hand damper somebody closed years ago, or a flex run pinched to a fraction of its diameter. A damper handle that sits across the duct means closed, and turning it in line with the pipe is a repair you can make yourself in ten seconds. If the handle is already open and the register still gives a trickle, the run is disconnected or crushed somewhere you cannot see, and why one room is colder than the rest walks through the other causes.
Where the break is depends on the house. In 1950s and 60s bungalows the ducts hang in an open or half-finished basement, and the usual find is a round branch knocked off its collar by a renovation or a stored ladder. In 1970s–90s two-storeys the second-floor runs climb through wall cavities and cross the garage ceiling, so a failed joint hides behind drywall and shows up as a cold room over the garage. Additions, bonus rooms and retrofitted second floors are often fed by flex duct through an attic, a kneewall or a crawlspace, where it sags, kinks around framing and gets its insulation jacket chewed open by mice and squirrels.
The repair itself is plain sheet-metal work done properly. A slipped round pipe goes back on its collar with three screws around the joint and sealant over the seam, so it cannot work loose again. Crushed or torn flex is cut out and replaced with a new length pulled tight and hung on wide straps, because a flex run left slack or bent sharply can lose most of its airflow even when it is intact. Rusted, flooded or rodent-fouled sections are replaced outright, and the leak that rusted them, usually a humidifier feed or an overflowing AC drain pan, gets dealt with on the same visit.
Some breaks should not wait for spring. A supply duct that has come apart in an attic blows warm, humid house air onto a cold roof deck all winter, and that moisture turns into frost and then into a ceiling stain. A disconnected run in a crawlspace heats the dirt under the house while the room above stays cold. If the damage turns out to be a design problem instead, such as undersized trunks or too few returns, the next step is ductwork installation and modification, and you can book a visit to find out which you have.
Signs a duct needs repair
- One register gives little or no air while the others are strong, and its damper is open
- A rattle, bang or whistle from one section of duct when the blower starts or stops
- Rust streaks, water stains or a sagging spot on a duct near the humidifier or the AC coil
- Dust, insulation fibres or a musty attic or crawlspace smell coming from one register
- A room that went cold right after a renovation, a pest problem or work above the ceiling
How it works
Which room, since when, and what changed: a renovation, a new furnace, a water leak, animals in the attic. Check the damper on that branch and the register itself before we come, since a closed damper is free to fix.
We measure airflow at the registers and static pressure at the blower, then follow the weak run outward from the trunk through the basement, attic or crawlspace. You see the break and get a written price before anything is cut.
The run is reconnected, replaced or re-hung, the joints are screwed and sealed, and airflow at that register is measured again so the result is a number. If drywall has to be opened to reach the duct, you know that before the work starts.
Common questions
Can I fix a disconnected duct myself?
In an open basement, often yes: push the round pipe back over its collar, drive three short sheet-metal screws around the joint and cover the seam with foil tape or mastic, not cloth duct tape. Leave it to a technician when the break is in an attic or crawlspace, when the duct is flex with a torn inner liner, or when the joint is on the return side beside the furnace.
Why does my ductwork bang when the furnace starts?
That is a flat panel of the trunk or plenum flexing in and out as the pressure changes, which the trade calls oil-canning. The fix is to stiffen the panel with a brace or a cross-break. It is also worth measuring static pressure, because a loud pop often means the blower is working against a restrictive filter or an undersized return.
Is duct repair the same as duct sealing?
No. Repair deals with a specific failure: a run that is off, crushed, rusted or chewed. Duct sealing treats the small leaks at every joint across a system that is otherwise intact. A house can need both, and the order matters: reconnect and replace first, then seal, then measure.
When is a duct beyond repair?
Replace the run when flex duct has a torn inner liner or a waterlogged jacket, when sheet metal has rusted through, or when rodents have nested inside it. Rework the system instead of patching it when several rooms are weak, or when static pressure stays above the blower's rating with every run connected. That is a design fault, and patching will not change it.
Do you repair ducts in rural homes with crawlspaces?
Yes. Farmhouse additions and older rural homes around Kilbride, Carlisle, Campbellville and Caledon sometimes carry their ducts through a crawlspace, where runs drop off their hangers, insulation gets wet and animals move in. We re-hang, replace and insulate those runs, and we tell you plainly when the crawlspace has to be dried out before new duct goes in.