How do you winterize a garage?

Front Range winters arrive fast. A chinook can drop temperatures 30 degrees in an hour, and January lows around Denver average below 20 degrees Fahrenheit. Running through a winterization checklist in October takes two to three hours and costs $50 to $300 in parts, but it prevents frozen pipes, jammed doors, and a heating bill that reflects every gap in the garage.

Step One: Check and Replace the Bottom Seal

The bottom seal wears faster than any other weatherstripping on the door. Pull your car out, close the door, and inspect the base from the inside. If you see light anywhere along the bottom edge, the seal is no longer doing its job.

For a flat concrete floor, a standard T-slot seal works well and costs $15 to $40 for a single-car door. For a floor with cracks, settlement, or a crown in the middle, a bulb seal or threshold seal provides better contact because the rounded profile compresses against floor irregularities. Threshold seals mount to the floor itself and cost $30 to $60 for a two-car opening. Either type of bottom seal replacement takes 20 to 30 minutes.

Also check whether the floor at the threshold has settled away from the door's closing path. A gap of more than 1/4 inch at the corners where the door meets the frame means the seal cannot compensate for the drop. A shim under the bottom bracket, a threshold seal, or a combination of both addresses this gap directly.

Choosing the right seal material also matters in Colorado. Silicone-based seals hold up better through freeze-thaw cycles than standard vinyl or rubber seals. The repeated temperature swings from below zero in January to 60 degrees in February cause standard vinyl to harden and crack faster than in milder climates. Spending a few extra dollars per foot on a silicone or EPDM seal pays off in longer service life.

Step Two: Inspect All Weatherstripping

Three separate zones seal the door's perimeter: the bottom seal, the side weatherstripping on the door stops, and the top seal along the header.

Side seals press against the door face when closed. They often wear flat or crack after five to eight years of Colorado temperature cycling. Run your finger behind the strip along the frame. A gap means cold air is entering. Replacement vinyl or rubber strips cost $10 to $25 per side and slide or staple into the door stop channel.

The top seal runs along the header and is easy to overlook. Check it from inside with the door closed. A thin strip of light along the header means the seal has pulled away or worn thin. Replacement header seals cost $10 to $20 and tack in place with staples or finish nails. This quick fix stops the cold air that otherwise works its way across the top of the door and down the interior wall.

Step Three: Lubricate Moving Parts

Cold temperatures thicken lubricants and make metal hardware contract. A door that moved quietly in September can grind, squeal, or move slowly once temperatures drop below 20 degrees Fahrenheit. Late fall is the right time for a full lubrication pass.

Apply silicone spray or lithium-based garage door lubricant to all rollers (spray the bearing inside the roller, not the tread surface), both ends of each hinge pin, the torsion spring (a light coat along the coil length), the bearing plates at the ends of the torsion bar, and the top and bottom sections of each vertical track.

Do not use WD-40 for this job. WD-40 is a water displacer and light solvent. It strips existing grease from the components and evaporates quickly, leaving the hardware under-lubricated within weeks. A garage door specific product with silicone or lithium as the active ingredient provides lasting protection through winter.

Step Four: Insulate the Door if Needed

An uninsulated single-skin steel door is the biggest thermal weak point in most garages. If the door lacks foam insulation, October is the right time to add it before the cold arrives.

A foam panel kit for a two-car door costs $75 to $150 at a home center and adds R-3 to R-8 depending on foam type and thickness. Installation takes two to three hours. After adding insulation panels, check the door's balance by disconnecting the opener and lifting the door manually to about waist height. If it falls back down, the springs need adjustment to compensate for the added weight. A spring adjustment costs $100 to $150 and protects the opener motor from working harder than it should through winter.

Step Five: Inspect for Pipe and Utility Gaps

Frozen pipes are a real risk in unheated Colorado garages that share a wall with the house interior. Water supply lines that run through the garage, or that enter the house through an uninsulated garage wall, are vulnerable when temperatures drop below 20 degrees Fahrenheit for several hours.

Check around any pipes that penetrate the garage walls or ceiling. Gaps larger than 1/4 inch around pipe penetrations let exterior cold air bypass wall insulation and chill the pipe directly. Seal them with expanding foam or caulk rated for exterior temperature ranges.

Check electrical outlets on exterior garage walls too. Standard outlets sit in open boxes against exterior sheathing, and cold air enters through the outlet holes. Install foam gaskets behind the outlet covers, available at hardware stores for under $1 each. This tiny fix reduces cold air infiltration at every outlet on an exterior wall.

Test the door's auto-reverse before winter too. Place a flat 2-by-4 board in the door's path and close the door with the opener. The door must contact the board and reverse. If it does not reverse, the system is not safe and should be serviced before winter use. A door that forces its way through ice buildup at the threshold without reversing can crack a panel or damage the bottom seal on the first cold snap.

One more area to address in the fall: check the weatherstripping on the personnel door between the garage and the house interior. This door is often ignored during garage winterization, but it is the last line of defense against cold air that has already entered the garage reaching the living space. A worn door sweep on the bottom and fresh compression weatherstripping on the frame seal that transition effectively. The materials cost under $30 and the installation takes 30 minutes.

Also look at the garage door opener itself. Cold temperatures affect battery backup systems in smart openers. If your opener has a battery backup module, test it by unplugging the opener from the wall and running the door two or three cycles. The door should operate at reduced speed but complete its full travel. If the backup fails the test, the battery needs replacement before winter, since power outages from ice and wind are most common in Colorado from November through March.

Finally, write down or photograph the condition of your door, seals, and springs in the fall while everything is accessible. A record of what was inspected and replaced makes the spring checkup faster and helps you track how quickly each component is wearing. Springs that were new two years ago need less attention than springs that were here when you bought the house.

G Brothers Garage Doors offers a seasonal tune-up covering lubrication, seal inspection, spring check, and safety testing. We serve the Denver metro and Front Range with free estimates and same-day service. Licensed and insured, 24/7 emergency availability.