One Double Door or Two Singles, and Getting the Size Right Before You Order

Published August 20, 2026

Most people choose a garage door the way they choose a front door, by looking at pictures. That works fine right up until the tape measure comes out, because the two decisions that actually govern the job are made long before anyone gets to colour. How many doors should there be, and what size can the opening in your wall actually take.

Neither question is difficult. Both are routinely skipped, and both are expensive to get wrong.

Why a Two Car Garage Has Two Possible Answers

Drive around Huntington Beach and you will see two car garages closed by a single wide door and two car garages closed by a pair of narrow ones. Sometimes on the same block, from the same builder, in the same year. Neither arrangement is a mistake.

A double door is one panel assembly, typically fifteen, sixteen or eighteen feet wide, running on one pair of tracks and lifted by one spring set on one shaft. A pair of singles is two complete door systems side by side, usually eight or nine feet each, separated by a post.

That structural difference is where all the other differences come from.

The Money Side

One door is cheaper, and by more than people expect.

A single sixteen foot door buys you one opener, one torsion spring assembly, one pair of vertical tracks, one horizontal track set, one bottom seal, one set of photo eyes and one installation visit. Two singles buy you two of every one of those items, plus the labour to hang two doors instead of one.

There is a California specific line in that list. Since the first of July in 2019, under SB-969, any residential garage door opener sold or installed in this state has to have a battery backup so the door still works in a power cut. That is a per opener requirement. Two doors, two compliant openers.

The photo eyes are per door as well. UL 325 entrapment protection means a pair of sensors mounted no more than six inches off the floor on each side of each door, wired back to that door’s opener.

Add it up and a double usually comes in somewhere near two thirds of what a matched pair of singles costs. The gap gets wider if you want insulated doors, because a pair covers more total square footage of panel than one door of the same opening width, and insulated panel is where the money goes.

What the Extra Money Actually Buys

Redundancy, and only redundancy. It is worth being clear about that, because it is a real benefit and it is easy to undersell.

When a torsion spring breaks on a sixteen foot door, that door is not going up. It weighs what it weighs and the spring was the only thing counterbalancing it. Anything parked behind it stays parked until somebody arrives with winding bars and a replacement spring. If both cars are in that garage, both drivers are stuck.

With two singles, the same failure takes out one bay. The other door opens normally. One car goes to work, one waits for the repair.

The same logic applies to a snapped cable, a door off its track, a burned out opener or a bent bottom section after somebody reverses into it. Every one of those events becomes half as disruptive.

Whether that is worth an extra thousand dollars or so is a household decision rather than a technical one. Two adults leaving for work at the same hour will use that second door. A household with one car and a workbench in the second bay will not.

Weight, Span and the Header Above the Opening

The other quiet difference is load. A sixteen foot insulated steel door can pass four hundred pounds. That is not a problem, but it does have to be respected in the specification.

Wide doors need a strut across the top section, because that is where the opener arm pulls. Without it the section bows in the middle over a couple of years and the top of the door stops sealing straight. Wide doors are often sprung with two springs on the shaft rather than one, both for capacity and so a single break does not drop the whole counterbalance at once.

Then there is the header. All of that weight arrives at the wall through the end bearing plates at each side and the centre bearing above the middle of the opening. On a wide door that concentrates a lot of load into one beam and into the framing at each end of it.

Two singles spread the same total weight across two smaller doors and put a post in the middle of the wall to help carry it. Everything is lighter, and every opener has an easier life.

Two Doors Have to Match, Permanently

This is the trade-off nobody mentions at the point of sale, and it is the one that catches people out years later.

Two doors sitting on the same street elevation read as a pair. They match properly only if they were ordered together, from the same run, in the same finish batch, with the same panel embossing and the same glazing layout.

Six or eight years later, one of them gets reversed into. Now you want to replace only that door, and three things have quietly moved. The panel profile may have been discontinued or revised. The paint batch will not be the same batch. And the surviving door has spent those years in coastal sun and salt air, which has taken it somewhere the new one is not.

From the sidewalk it looks like two different doors, because it is two different doors.

The practical advice is simple. If you choose two singles, treat them as one item for the rest of their life. When damage is bad enough to need a replacement, price the pair and decide with that number in front of you.

The Six Numbers

Now the size question, which is where most ordering mistakes are actually born.

Start with the rule that catches everyone: measure the opening, not the door. A garage door is deliberately larger than the hole it covers. It hangs behind the opening on the inside and seals against the stops. Measure the old door and order to that figure and the new one will not seal at the sides.

Width. Measure between the side jambs three times, near the floor, at roughly halfway, and near the top. Take the smallest of the three. Openings are seldom parallel, particularly where jambs are fixed to masonry, and the door has to clear the tightest point.

Height. Measure floor to the underside of the header at the left, the centre and the right. Take the smallest again, and while you are down there check whether the slab is level across the opening. A slab that slopes for drainage is normal and the bottom seal absorbs it, but past about an inch of fall you want a seal chosen for the job rather than the standard one.

Headroom. Measure from the top of the opening to the lowest obstruction above it, not to the ceiling. A water line, a light fitting, a joist or a storage rack all count. A conventional torsion setup wants about twelve inches. A low headroom track kit gets that to roughly four and a half. Below that you are into a jackshaft opener mounted on the wall next to the shaft.

Side room. The clear space from each side of the opening to the nearest obstruction, which needs to be around three and three quarter inches for the vertical track and its brackets.

Backroom. The depth from the opening back into the garage, normally the door height plus around eighteen inches for the opener rail and trolley.

Squareness. Measure both diagonals of the opening, corner to corner. More than about a quarter of an inch of difference and the opening is out of square, which shows up as a wedge shaped gap along the top of a closed door. It can be packed out at the jambs, but you want to know before the door is built, not after.

Write those six down once and every quote you gather afterwards is priced on the same job.

When the Opening Is Not a Standard Size

Standard singles are eight and nine feet wide. Standard doubles are fifteen, sixteen and eighteen. Heights are usually seven feet, with eight feet common on newer construction.

Plenty of housing here predates all of that. Openings turn up at seven feet six, at eight feet two, and at heights that stop noticeably short of seven feet. There are three routes out and they are not equally priced.

Framing the opening down with jamb material to the nearest standard width is usually the cheapest by a wide margin and takes a couple of hours. Ordering a made to order door fits anything but adds a premium and several weeks of lead time. Opening the wall out to reach a standard size is structural work with a properly sized header and a permit behind it.

Most of the time framing down wins. It is worth asking about before anyone quotes you a custom door.

The Opening Somebody Already Widened

One last thing to look for, because it turns up more often than it should.

At some point a previous owner wanted to fit a longer or wider vehicle and had the opening cut out. Sometimes that was done properly. Sometimes the header was cut and no beam went back in.

The signs are consistent. The top of the opening sags visibly along its length. The door binds at the top centre and nowhere else. There are stair step cracks in the stucco or drywall above the corners of the opening. And inside, the track brackets are lagged into a single flat piece of lumber instead of a real jamb.

A new door does not fix any of that, and hanging a heavier door on it makes it worse. The repair comes first, the measuring comes second, and the door is ordered to the repaired opening.

If you want the six numbers taken for you, or a straight answer on whether one wide door or two narrow ones suits your household, call Cultureconnectinc at (657) 794-9630.