Garage door bottom seals

A worn bottom seal on a 16 ft door is a small, cheap fix: sealing it on our standard 24×24 ft two-car worked example cuts about 3,500 BTU/hCComputed by our engineinsulateFirst() 'weatherstrip' measure on EXAMPLE_A_INPUT — lib/planner/roi.tsReport a problem of design-day heat loss for a $125 part. The right profile matters more than the brand — match the track you already have, or the seal won't hold.

Which seal fits your track

Most steel garage doors use a flat aluminum retainer channel screwed to the bottom edge. A T-style seal and a bulb seal both slide into that same flat channel — the difference is the rubber profile, not the track, so either works if the channel is in good shape.

A beaded seal is different: it needs a rounder, molded-in bead track on the door's bottom aluminum astragal, not the flat channel above. Don't buy a beaded seal for a flat retainer, or a T-style/bulb seal for a beaded track — neither will seat, and the door will leak air at the bottom corners even after installation.

A J-style or fin seal skips the track entirely — it tacks or nails straight to the bottom edge of the door. That makes it the fallback when a retainer is bent, rusted through, or missing, not a first choice when your existing track is still sound.

• Retainer intact, channel is flat → T-style or bulb seal, whichever profile you had before.
• Retainer intact, channel is a rounded bead track → beaded seal only.
• Retainer bent, cracked, or gone → replace the retainer track first, then pick a seal for it.

What sealing the bottom actually saves

On BayHeat's standard worked example — a 24×24 ft attached two-car garage in Chicago, R-13 walls, one uninsulated steel door, average drafts — tightening the door's bottom and perimeter by one tightness grade (the "weatherstrip" measure) removes about 12 %CComputed by our engineinsulateFirst() 'weatherstrip' measure — dQDesign / qDesign, lib/planner/roi.tsReport a problem of the garage's design-day heat loss, worth about $359/yr on electric heat at Illinois rates, for a payback under 0.3 yrCComputed by our engineinsulateFirst() 'weatherstrip' — cost / savingsPerYear.electricReport a problem year.

Savings vary. Find out why in the seller's fact sheet on R-values. Higher R-values mean greater insulating power.

That figure covers the whole weatherstrip package (bottom seal, perimeter stop, and service door), not the bottom seal alone — a bottom seal is the biggest single piece of it, since the bottom gap runs the full width of the door and sits right at floor level where cold air pools. See the full weather-stripping page for the perimeter stop and service-door kit that finish the job.

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Buy the right seal

What not to buy

Don't replace the whole door to fix a drafty bottom edge. A new insulated steel door is a multi-hundred-dollar-and-up project aimed at the door's panel and core, not its bottom seal — it fixes a problem you don't have yet while leaving the actual leak (the seal) exactly as worn as it was. Fix the seal first; a new door only earns its cost once the door panel itself, not just its gasket, is the thing failing.