Roller Door Heavy, Dropping or Won't Stay Up? Spring Tension Explained

Question 01

Why does my roller door feel heavy?

Usually because the spring has lost some of its tension. That's normal wear. B&D's roller door instructions say it's natural for springs to lose tension over time. The door weighs the same, so as the spring does less of the lifting, you do more. Dirty or bent guides, or a slipped running strip, can make it feel heavy too.

A roller door is one long steel curtain that rolls up around a barrel above the opening. The spring hides inside that barrel. When the tension is right, the spring carries most of the door and you (or the opener) just guide it. When the tension drops off, the door slowly gets heavier. It happens so gradually that it's easy to miss until the door starts coming down on its own.

The first four rows come from B&D's Roll-A-Door instructions, and the bulging row from B&D's advice on ballooning doors. Merlin's roller door opener manual says an opener that strains may mean the door is out of balance or a spring has broken. A bang is a different problem again. A spring that has snapped can't be re-tensioned, so read what to do about a broken spring before you touch the door.

Question 02

What does roller door spring tension do?

It balances the door. The spring winds up as the door comes down, then gives that energy back as the door rolls up, so the door feels far lighter than it is. A balanced roller door stays put when you let go of it partway. With too little tension it drops. With too much, it creeps back up.

Steel-Line's roller door installation guide describes the ideal setting. The door should be a little heavy in the down position so it stays down, and a little light in the up position so it stays up. B&D puts it another way: it should take about the same effort to open the door by hand as it does to close it.

The weights show why the spring matters so much. Steel-Line's homeowner manual says a roller door's weight can approach or exceed 150 kg, and that the force in the springs is roughly equal to the door's weight. Merlin's roller door opener manual says it shouldn't take more than 15 kg of effort to raise or lower a door at any point. The spring makes up the difference.

B&D adds that a roller door is usually set a touch tight when it's fitted or re-tensioned, because springs settle in. So a door that gets slowly heavier over the years is just normal wear.

Question 03

How can I tell if my roller door is out of balance?

Do a quick balance check on a closed door that's working normally. Lift it to about waist height and carefully let go. A balanced door stays about where you left it. If it drops or shoots up, the tension is off and it's time to call. Don't try it on a door that went bang.

1. 01Start with the door shut. If it has an opener, pull the release cord to put it in manual mode. Using the manual release explains how, and how to hook it back up after.
2. 02Clear the doorway. No kids, pets, cars or bins under the door.
3. 03Lift it to about waist height using the handle.
4. 04Let go carefully and step back. Watch what the door does.
5. 05Lower it gently. If it held its place, reconnect the opener. If it dropped or shot up, leave the opener off and tell Thom what you saw.

B&D and Merlin both describe this check for owners. Merlin's opener manual suggests trying the door by hand once a month, and both send you to a technician if it's out of balance or sticking.

Question 04

Can I tension a roller door myself?

No. Search how to tension a roller door and you'll find plenty of videos, but the makers are blunt about it. Steel-Line tells owners not to attempt it, at risk of serious injury or death. The spring in the barrel is wound tight all the time. One slip can let it unwind in a flash or bring the door down.

The videos make it look quick. The makers write their tensioning steps for trained installers. Even installers are told to tie the door up first and keep their head and body out of line with the wrench.

Steel-Line's manual leaves owners the cleaning and the checking. Anything to do with the spring is for qualified door people. So you look after the curtain and the guides, and a technician looks after the spring.

Question 05

What does a technician do when re-tensioning a roller door?

A technician makes the door safe first, then works out why it's heavy. If the spring has simply lost tension, it's adjusted a little at a time with the right tools, with a balance test after each change. The job's done when the door stays where you leave it and runs smoothly by hand and on the opener.

Going by the makers' own instructions for trained installers, the job runs like this:

1. 01Find the real cause. Dirty guides or a slipped running strip can feel a lot like low tension, so they're checked first.
2. 02Secure the door. Nothing gets loosened until the door and axle are held.
3. 03Adjust in small steps. Tension goes on or comes off a little at a time, with a balance test between each change.
4. 04Test the balance. The door should hold at waist height, stay down when shut and stay up when open.
5. 05Run it on the opener. If one is fitted, the door does a full cycle under power and the safety reverse gets tested.

If the spring is worn out or broken, more tension won't fix it. It needs replacing, which is booked as roller door spring repairs. What goes into the price of a spring job is covered in spring replacement cost.

Every job is done by Thom. He has 3.5 years of hands-on experience and has trained across multiple garage door brands, systems and businesses.

Question 06

My roller door has unravelled or won't stay up. Is it safe?

No. Stop using it. Merlin warns that an open door with weak springs, or one that's out of balance, can fall fast. It can come down on a person or a car. A bulging curtain can do more damage the longer it runs. Keep everyone out from under it and call. Don't try to wind it back on yourself.

An unravelled roller door often means the curtain has come loose on the roll and bulges out as it rolls up, instead of winding tight. B&D calls this ballooning. It lists spring tension set too loose or too tight among the causes, along with blocked or crooked guides, wear and tear, and rough weather. Whatever the cause, B&D says DIY tension work can be dangerous and to call a professional.

• If it's shut, leave it shut.
• If it's open and won't hold, don't walk, park or let kids play under it.
• Put the remotes away so nobody runs the opener out of habit.
• Leave the brackets and U-bolts alone, and don't try to wind the curtain back on.

Door stuck open overnight, or a car trapped inside? That's what 24/7 emergency garage door repairs are for. Thom takes emergency callouts around the clock across the Sunshine Coast.

Question 07

How much does it cost to re-tension a roller door?

Re-tensioning is booked like any other repair or service visit. Repairs and servicing are booked as a callout valued between $200 and $300 depending on the door size and the labour involved. If the spring turns out to need replacing rather than adjusting, ask Thom what your door needs when you call.

Spring tension and balance is one of the checks in every garage door service. So a small drop in tension gets picked up at a regular service, before the door starts dropping.

What the callout covers is in garage door service and repair costs. Thom works across the Sunshine Coast from his base in Maroochydore, from beachside Mudjimba to acreage in Ninderry. Call 0402 882 653 or book a callout.

Question 08

How do I keep a roller door running freely?

Keep the curtain and the guides clean, and leave the spring to a technician. Dirt and old grease in the guides make a roller door drag, and slamming it can work the brackets loose. A regular service then picks up a small drop in tension before the door starts to fall.

• Wash the curtain. Steel-Line says to wash it regularly to get salt and dirt off. B&D suggests clean water and a soft brush or cloth.
• Keep the guides clean. B&D's Roll-A-Door instructions say no grease or oil in the guides, because it clogs the running strips. Once they're clean, a silicone spray is fine.
• Don't let it slam. Steel-Line says jarring a roller door against its stops can loosen the brackets over time.
• Watch the brackets. If one moves at all, stop using the door and call.
• Don't touch the spring. Steel-Line's manual says even greasing the springs is dangerous work.

For coastal care and which sprays to use, see salt air and garage door rust. If the door has started to grind or rattle too, noisy garage doors covers what each sound usually means.