Definition
Extension springs sit alongside the horizontal portion of the garage door tracks, one on each side. Unlike torsion springs, they work by linear extension, they stretch open as the door closes and contract to assist on the way up.
Because an extension spring can become a projectile if it breaks under tension, modern installations require a safety containment cable running through the center of each spring. Any extension spring on a home today without a containment cable is a code and safety issue.
Extension springs were standard on residential doors from the 1960s through the late 1990s. Most homes built since 2000 use torsion springs instead because of their longer service life and safer failure mode.
Why it matters to Nashville-area homeowners
Many of the 1970s–1990s homes we service across Nashville and Chattanooga still have original extension-spring setups, often without safety containment cables, which is the first thing we add. If you have an older garage door with springs along the sides rather than a shaft across the top, confirm those safety cables are present before the next time you press the opener button.
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How this definition is reviewed
Definitions reviewed against UL 325 (Underwriters Laboratories Standard for Door, Drapery, Gate, Louver, and Window Operators), CPSC 16 CFR Part 1211 (federal residential garage-door-operator safety rule), DASMA technical data sheets, and current manufacturer specs from LiftMaster, Chamberlain, Genie, Clopay, and Amarr. Locality notes draw on in-the-field experience in Middle and East Tennessee homes built between the 1960s and the present.
