Why do my heating ducts tick or bang when the heater starts?

Heating ducts ticking or banging? Normal or a fault

The short answer

Light ticking, or a single soft pop as the heating starts or stops, is usually metal parts warming and expanding: the heater's plenum, the return air box, duct collars and outlet fittings. It settles once everything is warm. A loud bang from the heater itself as it lights, or rattling, flapping, grinding or squealing, is different and needs a check before you keep using the system.

Normal expansion noises

When the heater fires, hot air hits metal that was cold a minute earlier. Sheet metal boxes, joins and collars expand at slightly different rates and tick or click against their fixings, then do it again as they cool. Metal panels on the plenum or return air box can also flex with a soft pop when the main fan starts and the air pressure changes. If the noises are the same each time and stop once the system has warmed up, they're usually harmless.

Noises that need attention

A loud bang or whoomp from the heater cabinet as the burner lights can mean delayed ignition, where gas builds up before it catches. That's a job for a licensed gasfitter, so stop using the heater until it's checked.

Rattling, flapping or a whistling outlet often means a duct has come loose, split or dropped off its outlet in the roof space or under the floor, and that room will be getting less heat too. A zone damper stuck part-way can buzz or rattle. Grinding, squealing, or a rumble that rises and falls, points to the fan motor or its bearings.

Who looks at what

Burners, ignition and the heat exchanger are work for a licensed Type A gasfitter. Ducts, outlets, dampers and the electrical side, including the fan's supply and the controller, are work our team handles.

A loose or crushed duct is worth fixing for comfort and running costs, not just the noise. Federal guidance says ducts should be insulated to at least R1.5 with sealed joints, and a run that has come apart is heating the roof space instead of the room.

What you can safely do now

Note when the noise happens: at start-up, while running or as it shuts down.
Check whether one room is getting less airflow than usual.
Stop using the heater if it bangs loudly as the burner lights.
Leave ducts in the roof space or under the floor to a technician.

Services that can help

Ductwork Repairs & AirflowDamaged, leaking or poorly laid ducts repaired, replaced or rerouted.Gas Ducted HeatingGas ducted heaters installed, repaired, replaced and serviced.Air Conditioning Duct ReplacementOld, crushed or leaking ducts replaced in the roof space.

Sources for this answer

2 sources, with the date each was checked

1.YourHome (Australian Government): Ducts must be well insulated, to at least R1.5, and joints sealed to prevent condensation and leakage. The roof should have reflective foil insulation installed and be vented to dispel hot air. Zoned systems cool only… Accessed 30 September 2026.
2.Energy Safe Victoria: Type A appliances include domestic and light commercial type appliances such cookers, space heaters, central heaters, water heaters, catering equipment and leisure appliances. So, when looking to service and repair your… Accessed 30 September 2026.

General information for homes in Victoria. Every installation is different, so treat this as a starting point. Where this answer refers to Victorian safety or rental rules, the sources above have the current requirements.