When water seeps in during a Houston downpour, or you can see daylight or feel heat under a closed garage door, the flexible rubber bottom seal (the astragal) has worn out, cracked, or torn. Replacing it is one of the most satisfying and genuinely safe garage door DIY jobs: the old seal slides out of a retainer track along the bottom edge of the door, and a new one slides in. You work at the very bottom of the door, nowhere near the spring or cables, and the payoff is a dry, sealed, bug-tight garage.
What you'll need
- A tape measure
- A utility knife or sharp scissors
- Dish soap or silicone spray (as a lubricant to thread the seal)
- Pliers
- A helper for long doors (handy)
Recommended parts & supplies
- Garage door bottom weather seal — measure your door width and match the retainer type
- Garage door threshold seal — floor-mounted option for uneven concrete
- Garage door side & top weatherstrip — seals the sides and top of the opening
- Bottom seal retainer track — if your door has no retainer or it’s damaged
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Step by step
- 1
Identify your seal and retainer type
Most modern doors have an aluminum retainer channel along the bottom edge with one or two grooves; the rubber seal has matching beaded edges (a T-shape or a P-bulb) that slide into those grooves. Older wood doors may have a seal that’s simply nailed on. Look at your bottom edge and note the style so you buy a matching replacement.
- 2
Measure the door width
Measure the full width of the door and buy bottom seal a foot or two longer than you need — you can trim the excess, and having extra prevents coming up short. Bring your measurement and a photo of the retainer to match the profile.
- 3
Open the door partway to reach the bottom edge
Raise the door to about waist height so you can comfortably work along the bottom, then leave it there. Do not disconnect the opener or touch the spring. If the door won’t stay put on its own at that height, that’s a spring warning sign — lower it and call a pro rather than forcing this job.
- 4
Slide the old seal out
Pull the old rubber seal out through the end of the retainer track — grip it with pliers and work it out along the channel. If it’s brittle and tears, keep pulling the pieces until the grooves are empty. For a nailed-on seal on a wood door, pry the old strip and nails off.
- 5
Clean the retainer channel
Wipe out the aluminum channel so dirt and old rubber crumbs don’t block the new seal. A clean groove makes threading the new seal far easier.
- 6
Thread in the new seal
Line up the beaded edges of the new seal with the grooves and feed it in from one end. A little dish soap or silicone spray on the beads acts as a lubricant and helps it glide through. On a wide door this is much easier with a helper pulling from the far end while you feed. Keep the seal flat and untwisted as it goes.
- 7
Center, trim, and test the seal
Once threaded, center the seal so it overhangs evenly on both ends, then trim the excess with a utility knife, leaving a little bit past each edge. Close the door and check the fit: the bulb should compress against the floor with no gaps. If your concrete is uneven and light still sneaks through, a floor-mounted threshold seal pairs well with the bottom seal to close the gap.
When to call a pro
Replacing the bottom seal, side weatherstrip, and threshold are all safe homeowner jobs. Call a professional if the door won’t stay open at waist height while you work — that means the spring can’t hold the door’s weight, which is a spring or cable fault you must not attempt yourself. Also call if the bottom edge of the door itself is bent, rusted through, or if the retainer is torn off and the door section is damaged. And as always, if you notice a frayed cable at the bottom bracket or a gap in the spring coil overhead while you’re down there, stop and bring in a technician — those components carry lethal tension.
Get a free quote from a local pro
No obligation — a licensed, insured local Houston partner will reach out. Available 24/7 for emergencies.
How to Replace a Worn Garage Door Bottom Seal (Weatherstrip) — FAQ
Why is water coming under my garage door?
How do I know what size garage door bottom seal to buy?
Is replacing a garage door seal a safe DIY job?
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