Signs your garage door seal needs replacing
B&D gives five signs a bottom weather seal is due. The rubber is cracked, brittle, flattened in spots or pulling away. Water pools inside after rain. The garage turns draughty, or warms and cools with the weather outside. Pests show up more, sometimes with chew marks or fraying on the seal. And the door rattles or vibrates as it shuts.
Seals do not last forever. B&D says most weather seals last several years depending on the climate and the use they get, and suggests looking them over once a year for cracks, gaps or hardening. It puts most brush seals at three to five years.
How to find the gap in a garage door seal
Shut the door on a bright day
B&D and Steel-Line both suggest this test. It needs no tools and takes a couple of minutes.
Stand inside with the lights off
Steel-Line's version has you inside the closed garage in the dark, looking for wherever daylight comes through.
Note where the light shows
A line along the floor points to the bottom seal, or to the floor itself. Light down the sides or across the top points to the moving gap, which B&D says to check for along those edges.
Take a photo from inside
A picture of each line of light tells the door specialist more than any description, and it goes straight into the note on the form.
Which seal closes which gap
| Where it sits | What it keeps out | |
|---|---|---|
| Bottom seal | Along the bottom rail, against the floor. Steel-Line roller doors carry a PVC weather seal in the aluminium bottom rail | Water, dust and draughts under the door |
| Brush seal | Dense bristles in a carrier along the top or sides of the opening, tips just touching the door, as Steel-Line describes it | Dust, smoke, salt, insects, spiders and mice, Steel-Line says |
| Roller door top seal | Gliderol's fit-to-door top seals nest inside the door as it rolls up, which suits garages with little headroom | Gaps up to 50mm as standard |
| Sectional top and side brush seals | Behind the jambs and lintel, on Gliderol's range | Gaps up to 19mm, plus embers, smoke, driving rain and coastal corrosion |
| Perimeter seals | Right round the door: B&D's Panelift Icon has 360° perimeter seals and its standard Panelift does not | Leaves and dust |
Brush seal or rubber seal?
Often both. Steel-Line puts it neatly: 'A rubber seal handles the floor, a brush seal handles the moving gap, and some garages need both.' It also says a brush seal will not cure dust that comes in under the door from a worn bottom seal or an uneven floor, so if the light in your test was along the ground, a brush seal alone will disappoint.
Brush seals are an option on plenty of doors rather than a standard part. Steel-Line offers one for the aluminium guides of select roller doors, and recommends adding them to its Mammoth insulated sectional doors.
Roller door seals and Nylofelt
On a roller door the bottom seal lives in the bottom rail, and the sides can take a brush seal in the guides. Top seals are a separate part again, and Gliderol's fit-to-door type is made for roller doors in low garages.
Nylofelt strips come up when a Roll-A-Door gets stiff. B&D's Series 1 manual puts them first on its list for a door that is hard to run: check they haven't slipped and jammed, then that the guides are straight and clean. If the door is still heavy going after that, the manual says the spring tension needs an experienced door technician, which is never an owner's job. The broken spring guide explains why.
Seals for bushfire areas and the coast
If your home has a Bushfire Attack Level, Gliderol says the BAL rating decides whether flame retardant seals may be required. Its flame retardant seals are PA6 nylon that self-extinguishes on ember contact, deemed to comply with AS3959:2018. Steel-Line rates its Nylon Brush Seal UL94-V2 and says it suits ember protection to AS3959.
Adding seals does not turn an old door into a tested one. B&D says retrofitting seals to an existing door has not been tested by the CSIRO, so it cannot be rated BAL-40. Your BAL assessment and the building surveyor set the rules for your home, so pass the rating on to the door specialist if you have it.
Near the sea, Steel-Line says homes should check that a seal suits those conditions. Salt is one of the things a brush seal is meant to keep out, so ask what the bristles and carrier are made of.
Some seals sit next to parts you must leave alone
The bottom corners of a sectional door carry the lift cable fixtures, and Steel-Line warns never to loosen any fastener on them, because the spring could unwind or an open door could fall. Leave any seal work near those corners to the door specialist, with the door closed and the opener disengaged.
What fitting a new garage door seal involves
The door specialist finds the gap first, checks the floor under the door, and then picks a seal that suits the door's make and model, the gap size and your conditions, including any BAL rating. Bottom seals, side seals and top seals are often different parts from different ranges, so the right one depends on what your door already has.
A brush seal has to be set with care. Steel-Line says the bristles should only skim the door, because too much contact causes drag, and a door that drags works its opener harder. If the door is motorised, ask for its travel limits and force to be checked after a new bottom seal goes on: ATA's GDO-6 manual lists setting both as part of a technician's service. Then watch the reversing test before they leave.
Seals are wear parts. B&D's warranty brochure gives them a 1 year warranty and treats replacing them at a regular service as normal wear and tear, so a cracked bottom seal on an older door is usually a repair you arrange rather than a claim.
What you can do, and what to leave
You can
- Run the daylight test and photograph each gap
- Vacuum or soft-brush a brush seal each season, as B&D suggests
- Keep high-pressure water off brush seals
- Check the bottom seal once a year for cracks or hardening
- Note when the water, dust or pests started
Leave to a door specialist
- Fitting bottom, side and top seals
- Anything near the cable fixtures at a sectional door's bottom corners
- Choosing seals to suit a BAL rating
- A roller door that has become hard to run
- Resetting the opener's limits and force after a new seal
What we would do
Do the daylight test before the door specialist comes, and photograph every line of light you can see from inside. It shows at a glance whether the door needs a bottom seal, a brush seal or both, and on which sides, so the right parts can come on the first visit.