How to Seal a Garage Door Against Rodents
Why this matters
An attached garage is the biggest single opening in most houses, and the door that closes it is sealed with rubber and vinyl that flatten, crack and get chewed. The bottom corners are the weak spot: the bottom seal ends a little short of the jamb, the side weatherstrip stops a little above the floor, and the gap where they fail to meet is often wide enough for a mouse when the rest of the door looks tight. A tech who seals every penetration on the house and skips the garage door corners will be back on a callback with mice still in the kitchen. This card owns closing the garage door: finding the gap, replacing the bottom seal, adding a corner guard and proving the door still works. Material choices and the gap thresholds (a mouse passes about 1/4 inch, a rat about 1/2 inch) are owned by 'Rodent Exclusion Materials and Opening Sizes'.
Where the gaps are
GARAGE DOOR FROM OUTSIDE, DOOR CLOSED
top weatherstrip on the header
+==========================================+
S | | S
I | | I
D | door panels | D
E | | E
| |
|__________________________________________|
X bottom seal in its retainer, on slab X
SIDE = side weatherstrip nailed to each jamb,
sealing against the door face
X = corner gap at each jamb, where the bottom
seal ends and the side strip stops short
of the floor
The top weatherstrip rarely matters for rodents, though wasps and spiders use it. The bottom seal fails along its length when it flattens or the slab is uneven, and a sloped slab puts the widest gap at one end. The corners fail even on a new seal, because nothing on a standard door is designed to close them.
Protection before you touch the door
Take the opener out of the job first. Unplug the opener, or switch off its dedicated circuit, before your hands go near the bottom of the door or the track. A family member pressing a remote while you are lying at the door bottom is the injury this step prevents. Plug it back in only at the operating test in step 6.
Never touch the springs, the lift cables or the bottom brackets. The torsion spring above the door, or the extension springs along the tracks, hold the door's weight as stored energy, and the bottom bracket at each lower corner is where that energy is anchored through the lift cable. Loosening a bottom bracket fastener can release the cable with enough force to break bones. That hardware is a garage door technician's work: the protection is that you do not disturb it, and if your job seems to require it (the seal retainer is held by the bracket, or the bracket is the only thing in the way), stop and refer it. For an employer whose crew services that hardware, stored-energy control follows, in substance, 29 CFR 1910.147.
When the door must be partly open, lock it there. Sliding a new seal into the retainer usually means raising the door to about waist height. With the opener unplugged, the door moves by hand only once the opener is disconnected: pull the emergency release with the door fully closed, then lift. A door that is heavy to lift or will not stay put at waist height has a spring problem; lower it and refer it. Clamp locking pliers on the track just below a roller on each side so the door cannot come down, and never pull the emergency release cord with the door open: if a spring is broken, the door falls.
Gloves and a look first. Garage corners collect droppings, nest material and spiders. Wear gloves, do not sweep droppings dry, and follow 'Rodent Droppings and Hantavirus for the Trades' when there is more than a few.
Steps
Start state. You need: a flashlight, the 1/4 inch and 1/2 inch drill bits used as go gauges, a replacement bottom seal matching the retainer, rodent-resistant corner guards made for garage doors, a drill and corrosion-resistant screws, a utility knife, locking pliers, dish soap and water in a spray bottle, and the camera. Check before you begin: the door runs smoothly on the opener, does not bind or slam, and the springs and cables look intact. A door that already misbehaves is referred before you change anything, so nobody blames your seal for its fault.
Close the door and read it from inside with the lights off. Stand inside the garage, door shut, overhead lights and the opener light off, and look along the bottom and up each side. Daylight is the map: a thin line along the bottom, a bright triangle at a corner. Then go outside and confirm with the gauges at each corner and every place you saw light. Reason: gaps on a garage door are rarely visible from outside in daylight, and a gauge finds a gap a tape would round down. Skip it and you replace a bottom seal and leave the corner gap that was the real entry.
Record the widest point and decide what fixes it. A bottom seal that touches the slab everywhere but the ends needs only corner guards. A seal that is flattened, cracked or gnawed along its length gets replaced. A gap that a new seal cannot take up, because the slab drops away at one end, needs a taller seal or a floor-mounted threshold seal, and a threshold changes how water runs off the slab, so discuss it with the customer first. Reason: the fix is chosen from the measurement, not from what is on the truck.
Replace the bottom seal if it failed. Raise the door to about waist height and lock it on both tracks. Look at the end of the retainer: most steel doors use an aluminum retainer with T-shaped or bulb channels that the seal slides into from one end. Take the old seal out, cut a short piece to compare the profile, and match it; profiles and T widths vary between door makers, so match the old piece rather than guessing. Mist the channels and the new seal with soapy water and pull it through from one end, two people if the door is wide. Trim the ends about 1/2 inch long so the seal compresses into the corners rather than stopping short. Unlock and lower the door by hand, opener still unplugged. Reason: the trimmed-long ends are what keep the corner from reopening. If the seal is nailed to a wood door bottom or the retainer is bent or torn, refer the retainer to a garage door company; a seal slid into a damaged retainer pulls out at the first freeze.
Fit a rodent-resistant corner guard at each jamb. With the door down, hold the guard against the jamb at the bottom corner so its flexible edge meets the door face and its lower edge closes the space between the end of the bottom seal and the floor. Fasten it to the jamb with the screws its maker supplies or specifies, into solid framing, not just the trim. Reason: the corner is the one gap a standard door leaves open, and a vinyl side strip that reaches the floor is still vinyl, which mice gnaw. Skip it and a correctly replaced bottom seal still leaves a mouse-size triangle at each end.
Replace a chewed side weatherstrip. If the side strip is gnawed or pulled away from the door face, replace it with a new strip fastened so its flexible edge lightly touches the door all the way to the floor, set the same way the old one was. Too tight and the door drags and the opener strains; too loose and you have only moved the gap up the jamb.
Restore the opener and prove the door still protects people. Plug the opener back in and reconnect the door to it per the opener's manual (many trolleys re-latch when the opener first runs). Run the door through two full cycles and watch the bottom: it should settle onto the slab, compress the new seal and stop, not stall above the floor or bounce back up. Then run the two safety checks the opener's manual describes: interrupt the photo-eye beam while the door is closing (the door must stop and reverse) and lay a board flat on the slab in the door's path as the manual specifies (the door must reverse on contact). Stand to one side of the door, never under it, and keep the customer and pets out of the opening while it cycles. Reason: a taller or new seal changes where the door meets the floor, which can change how the opener reads the close. If it fails either reversal test, does not fully close, or reverses off the new seal, unplug the opener, tell the customer the door must not be used on the opener, and refer it to a garage door technician; you do not adjust limits or force.
Finish test
With the door shut and the garage dark, no daylight at the bottom or either corner. Neither gauge enters anywhere along the bottom or at the corners. The door closes fully and passes both reversal checks. Photographs of each corner, before and after, are on the ticket.
Worked example: two-car door on a mouse account
The account: mice trapped in the kitchen, which shares a wall with an attached two-car garage. The door is 16 feet wide.
Step 1. From inside with the lights off, a thin line of daylight runs along the middle third of the bottom, and a bright triangle shows at the east corner. Outside, the 1/4 inch shank slides in at the east corner, where the gap measures about 3/8 inch and closes to nothing about 18 inches along the door. The 1/2 inch shank does not enter anywhere. At the west corner, the gap is about 1/8 inch. Along the middle, the seal is flattened and cracked, with a gap of about 1/8 inch.
Step 2. The east corner is a mouse entry (3/8 inch is over the 1/4 inch threshold and under the 1/2 inch rat threshold). The middle and the west corner are under the mouse threshold, but the seal is cracked vinyl, and a chewable edge just under the threshold gets treated as an entry, per the materials card. The slab is level enough that a new seal will take up 1/8 inch. Decision: replace the bottom seal and fit corner guards at both jambs.
Step 3. Door raised and locked on both tracks, opener unplugged. The retainer is aluminum, in good shape, double T channel. The tech matches a cut piece of the old seal, slides in 16 feet of new seal plus about 1/2 inch at each end, and lowers the door by hand.
Step 4. A corner guard at each jamb, screwed into the framing behind the trim. The east guard covers the triangle the gauges found.
Step 5. The side strips are sound; not replaced.
Step 6. Opener plugged in. On the first close the door stops about 1/4 inch above the slab and reverses off the new, thicker seal: the opener's down limit was set for the flattened seal. This step's stop rule fires: door lowered, opener disconnected with the door closed and unplugged, customer told to run the door by hand until the door company resets the limit, referral written on the ticket. The tech does not touch the opener settings. The exclusion itself is done; the door is shut by hand and the corners pass the daylight check.
Follow-up visit. The door company reset the limit the next day; the door closes and reverses normally on both checks. Kitchen captures were two the week before the seal and none on the next two services, and a patch of tracking dust at the east corner shows no tracks.
What changes the method
- A rat account. The same steps, but heavier corner guards with metal at the bottom edge and a seal retainer in good condition matter more, because rats chew through vinyl corners a mouse would leave alone.
- A wood door or a door with no retainer. The seal is nailed or stapled to the bottom rail. Replacing it is often still pest-tech work, but a rotten bottom rail is a door repair; refer it.
- The garage is sealed and mice still reach the kitchen. Check the door between the garage and the house: a missing sweep there passes mice from a garage they already live in. For a callback where the garage door corner itself was the route, see 'The Mouse Callback Traced to a Garage Door Corner'.
References
- See related: Rodent Exclusion Materials and Opening Sizes
- See related: The Mouse Callback Traced to a Garage Door Corner
- See related: Rodent Droppings and Hantavirus for the Trades
- 29 CFR 1910.147 (control of hazardous energy), for the springs and cables this card routes to a garage door technician
- The garage door opener manufacturer's manual for the photo-eye and contact-reversal checks