What gets replaced: a section, not a panel
A sectional door is four or five horizontal sections, hinged to each other, with a roller at each end of every section running in the tracks. The rectangles stamped into the face are the panel design, not separate parts: the replacement part is a whole section, the full width of the door, and the hinges and rollers move over to it.
The bottom section carries the bottom brackets the lift cables hook to and the floor seal; the top section carries the opener arm bracket. Both are different parts from the sections between them, which is why the label inside the door, with the model and the manufacturing date, is the first thing to photograph.
Source: Amarr: Garage Door Replacement Panels, When to Repair or Replace
Strut, bracket or new section
A section that is cracked, bowed or pulling away from a hinge, but still in one piece, can usually be held straight with a horizontal reinforcement strut across its full width or a bracket at the hinge. That keeps the door in service on the visit, with no part to order and no color to match. On eight invoiced jobs, in Chelmsford, Fitchburg, Andover and Arlington, that was the repair.
A section that is torn, creased through, rusted through along the bottom or no longer holds its shape needs replacing. A cracked top section also needs its cause found: the usual ones are an opener pulling on a section with no strut, a door out of balance, or a close limit set so the opener keeps pushing after the door is down. Replacing the section without that check sets up the next crack.
Source: Amarr: garage door FAQs (cracked top sections, springs and cables)
What replacing a section involves
For a bottom section, the lift cables hook to its brackets, so the spring tension is released first and the cables unhooked before the section comes out. The new section goes in with the bottom brackets and a new floor seal, the cables go back on, the springs are re-tensioned and the door is balanced. That is also why the bottom brackets must never be unbolted on a door that is still under spring tension.
For a middle or top section, the door is run to where the section can be reached, the hinges and rollers come off it, the section slides out of the tracks and the new one slides in. Last comes the opener's reversing test, so a door with a new section stops when it should.
Source: 16 CFR 1211.16, the safety instructions every opener manual must carry (eCFR)
When a new door is the better buy
Three cases: the maker no longer makes a section for the door, more than one section is damaged, or the door is an old single-layer steel door whose other sections are not far behind. For comparison, panel replacement runs $500-$1,500 and a new single-car door installed runs $1,578-$7,980; a new door comes with new hardware, new seals and a warranty.
Installed prices for every Amarr collection, by size, are in the Door Builder, and the written quote matches it. The full comparison is in when to repair or replace a garage door.
