Why Does My Garage Door Only Have One Torsion Spring? A Quality Inspector's Take

Most single-car garage doors only need one torsion spring—up to about 8 feet wide and 7 feet tall, that's a normal spec. If the door is wider, taller, or insulated steel, one spring is probably undersized. I've rejected shipments for less.

I'm a quality/compliance manager at a hardware company. I review roughly 200 unique items each year before they reach customers, and in 2025 I've rejected about 8% of first deliveries over spec mismatches. So when someone asks me why does my garage door only have one torsion spring, I don't hear a homeowner panic question. I hear a specification question.

The short answer: door weight and cycle life, not just width

One torsion spring is fairly common on lighter single-car doors. Two springs become the safer call when the door is wider, heavier, or needs a longer cycle life. But more springs doesn't automatically mean better. The spring's wire gauge, inside diameter, length, and winding direction all have to match the door's measured weight. According to DASMA guidelines (dasma.com), torsion springs should be selected based on door weight and cycle frequency—not width alone.

I think people overfocus on the count because it's visible. A 16-foot door with one long spring looks scary. An 8-foot door with one spring is often fine. The number is only one variable.

Why I use the same logic on a Stanley tool box STST16410

Take the Stanley tool box STST16410. It's a good mid-size box, but I didn't approve it because of the brand. I loaded it with 25 lb of mixed tools, dropped it from 4 feet, and cycled the latch 50 times. It passed. The label doesn't matter if the latch fails under load—same as a garage door.

I'm not saying every Stanley product is automatically right for every job. I'm saying the STST16410 earned its spot through testing, not name recognition.

The Stanley fibreglass club hammer STHT0-54128: a small spec detail changed my opinion

The Stanley fibreglass club hammer STHT0-54128 is another example. The Anti-Vibe handle is pretty comfortable for a club hammer, and the fiberglass shaft doesn't swell in humid shop conditions. I wasn't going to include it in our approved list until I checked the head-to-handle fit under impact. It held up. What surprised me was the balance—it's slightly head-heavy, which is useful for driving stakes but not what you'd want for fine work. That's why spec review matters.

When I compared it to a cheaper hammer side by side, the difference wasn't the brand sticker. It was the handle absorbing shock instead of sending it into my wrist.

One torsion spring vs. two: a comparison I'll always remember

When I compared two identical 8-foot doors side by side—one with a single torsion spring, one with two—the single-spring door cycled fine. The two-spring door felt smoother, especially near the top. That contrast made me realize the second spring isn't always about preventing catastrophic failure. It's about reducing fatigue on the spring, cables, and opener over thousands of cycles.

Looking back, I should have spec'd two springs for our 16-foot shop door from the beginning. At the time, the budget said one, and the supplier's standard configuration made it seem fine. The original install didn't fail. It was the slow wear on the opener that cost us more in labor and downtime. If I could redo that decision, I'd spend the extra money upfront.

Ball valves and air compressors: same spec-first logic

A 1/2" FNPT bronze gas ball valve looks like a simple part, but it's not. The thread engagement, seat material, and pressure rating all have to match your system. Bronze is a common material for this size because it resists corrosion better than carbon steel and costs less than stainless. Based on major supplier quotes in early 2025, a 1/2" FNPT bronze ball valve runs roughly $15–$35; verify current pricing. But don't pick a valve by price. I once saw a cheaper valve fail a pressure test because the stem packing wasn't rated for the full WOG spec.

Same with an air compressor from Northern Tool or anywhere else. Don't stop at the CFM number. Check the tank's ASME certification stamp, the drain valve location, and the duty cycle of the pump. I've seen a 20-gallon compressor with a good pump and a drain valve that's almost impossible to use without contorting your body. Minor detail, major annoyance.

Even after choosing the bronze valve for a pressure test rig, I kept second-guessing. What if the spec really required stainless? The week between ordering and delivery was stressful. I didn't relax until I installed it and the threaded test showed zero leaks.

What I'd do if I found one torsion spring on my own garage door

1. Measure the door width and height. Under 8 feet wide and 7 feet tall, one spring is often within spec.
2. Weigh the door or check the manufacturer's spec. Insulated steel doors can be 20–30% heavier than plain aluminum.
3. Look at the spring's wire gauge and length. A thicker, longer single spring might be correctly designed.
4. If you're not sure, call a licensed door technician. A 30-minute inspection is cheaper than a cable failure.

Bottom line: one spring can be right, and two can be wrong

I'm not a garage-door engineer, and I'm not a plumber. I'm the person who has to read the spec, test the sample, and decide whether to send it back. A single torsion spring can be completely correct on the right door. Two springs aren't automatically better if the spring geometry doesn't match the door. The answer comes from measured weight, spring dimensions, and cycle rating—not opinions.

What was accepted in 2020 may not hold in 2025. Door weights changed, insulation standards changed, and spring specs changed. The fundamentals haven't changed: the spring has to match the door. The execution has improved, and so has the tooling around it.

Whether it's a Stanley tool box STST16410, a Stanley fibreglass club hammer STHT0-54128, or a torsion spring, I look for the same three things: correct spec, verified performance, and no hidden surprises. That's the standard I use at work, and it's the standard I'd want after my own door.