Garage Door Bottom Seal Replacement: what to note first

One end of the bottom seal has slipped out of its channel and hangs down like a loose shoelace. Each time the door closes it folds under, each time it opens it flaps, and the gap beside it keeps growing.

Worth answering before the call

Is the door a single or a double, and roughly how wide? Are the side and top weather strips also worn or torn? What is getting in: light, drafts, water, snow, leaves or pests?

My garage floor is uneven. What are the options?

Three, and they can be combined. A taller bulb-style seal compresses more and follows a modest dip or crown. A threshold seal fixed to the floor follows the slab's existing contour and gives the door a raised, consistent line to land on where it is dished or sloped. And where the floor has heaved or broken up badly, grinding or patching the concrete is a separate job that makes any seal perform better. The gap map from the first look shows which applies.

Is the seal on an insulated steel door different?

Sometimes. Many insulated doors have the seal channel moulded into a plastic cap that wraps the bottom rail, which takes a specific profile rather than a generic one. If that cap is cracked or the channel has opened, a screw-on aluminum retainer can be fitted over the rail so a standard T-style or bulb seal can be used from then on. Identifying the retainer at the first look settles which route applies.