Broken Spring - Replace One or Both Decision Tree

Why this matters

A 2-spring system with one broken spring and one intact spring is the most common service call in residential garage door work. The customer asks "can you just replace the broken one?" Yes you can, and no you should not. The intact spring is at the same age, same cycle count, same metallurgical fatigue as the broken one, and replacing one alone schedules a return trip in 2 to 12 months when the second one fails. But pair-replacement on a low-cycle door where both springs were just installed last week is overkill. This tree gives a defensible rule based on cycle count, age, and the customer's tenure, plus the conversation script that makes "both springs" the obvious recommendation.

Symptom presentation - the broken-spring call

Three field shapes:

• Customer reports "I heard a bang and now the door won't open": classic spring failure; one or both broke, usually one. Door opener will not lift the dead weight of an unsprung door.
• Door opens slowly and the opener strains audibly: spring is weakened but not yet broken; or one of a pair has broken and the other is carrying the load.
• Door opens but reverses or won't stay open at mid-height: spring balance is wrong; could be a broken spring (most likely on a 2-spring system) or wrong-spec replacement spring.

Inspect the springs first thing on any service call. A broken spring shows a clear gap (1/4 in or larger) where the wire has separated. A weakened spring shows pre-failure indicators: stretched coils at the ends, rust pitting, paint flaking from the wire surface.

Quick checks at the door

Four reads in the first 2 minutes:

1. Spring count: 1 spring (single-car residential typical), 2 springs (larger residential and 2-car), 3+ springs (commercial). Single-spring system is always "the one spring."
2. Spring type: torsion (above the door, parallel to the header) is the residential and commercial standard; extension (above each horizontal track) is older residential, less common, and replaced differently.
3. Spring condition - both: even if only one is broken, inspect both. Stretched ends, rust pitting, paint failure on the wire surface indicate the intact spring is past mid-life.
4. Spring spec stamp: most torsion springs are marked with wire size, inside diameter, and cycle rating. Document the spec to ensure replacement matches. Mismatched springs lift unevenly and stress the door.

Isolation tree

1. Single-spring system? Yes → replace the one spring; pair-replacement doesn't apply. No → continue.
2. Both springs broken? Yes → replace both. No → continue.
3. Was the existing spring installation done within the last 12 months? Yes → the intact spring is essentially new; one-spring replacement is acceptable IF the broken spring shows clear manufacturing defect (rare). No → continue.
4. Is the intact spring showing pre-failure indicators (rust pitting, stretched coils, paint loss)? Yes → replace both. No → continue.
5. Has the door been in service over 5 years and there's no record of prior spring replacement? Yes → both springs are at end-of-life cohort; replace both. No → continue.
6. Customer is selling the home or transitioning ownership? Yes → both springs as a warranty/disclosure consideration. No → continue.
7. Customer explicitly insists on one-spring replacement after being informed of the tradeoff? Document the customer's choice in writing; replace one with a stated "no warranty on the intact spring" notation.

Confirming the diagnosis - cycle count math

Residential torsion springs are sold by cycle rating. Common ratings:

• 10,000 cycles: stock builder-grade; typical 5 to 8 years residential life at 3 to 4 cycles per day.
• 20,000 cycles: mid-grade upgrade.
• 30,000 to 50,000 cycles: high-cycle premium residential or light commercial.
• 100,000+ cycles: commercial application.

A cycle is one open + one close. Typical residential is 1500 to 2000 cycles per year. A 10,000-cycle spring at 1500 cycles per year averages 6 to 7 year life. If a spring breaks at year 6 on a 10,000-cycle pair, the other spring has roughly the same remaining service - which is to say, very little.

Confirming - the pair-replacement conversation

The script that gets the customer to the right answer without feeling sold:

• "You have a 2-spring system. The springs were installed at the same time, they've carried the same load for the same number of cycles, and they're at the same point in their life. The intact spring isn't broken yet, but it's at the same age. If I replace only the broken one, statistical fatigue says the other one breaks in 2 to 12 months. That's a second service call and another trip charge. Pair-replacement now eliminates that. The cost difference is the second spring; labor is essentially the same because the truck is here and the door is down."

For a customer who pushes back hard on one-spring:

• "Understood. I can replace just the broken one today. I'll document on the work order that the intact spring is at end of life cohort and the recommendation was pair-replacement. There's no warranty implication on the intact spring because we didn't replace it. Sign here so we both agree on the scope."

Confirming - spring spec verification

When replacing, the new spring(s) must match the door's lifting requirement. Three measurements:

1. Wire diameter of the existing spring (or specified by door manufacturer for the door's weight).
2. Inside diameter of the existing spring (typically 1-3/4 in or 2 in for residential).
3. Wound length of the existing spring.

Wrong-spec springs lift unevenly (binding, door-out-of-balance) and over- or under-load the opener motor. A spring chart from any major manufacturer (LiftMaster, Genie, Wayne Dalton, Clopay) cross-references door weight and door height to required spring spec.

Remediation execution standards

Spring replacement (torsion, 2-spring residential):

References

• ANSI/DASMA 102, Specifications for Sectional Garage Doors.
• ANSI/DASMA 116, Specifications for Counterbalance Mechanisms for Garage Doors (torsion and extension spring standards).
• UL 325, Standard for Door, Drapery, Gate, Louver, and Window Operators and Systems.
• OSHA 29 CFR 1910.211 (general industry definitions including powered door work).
• IDA / International Door Association Best Practices for Torsion Spring Service.