Guest Post: No, You Can't Add Vents to a Jacket

By Manton

Among the many frequently asked questions on the various clothing fora (and above all Style Forum, the one I look at the most), “Can I get vents added to my ventless jacket?” is the easiest to answer, and yet it comes up again and again.

The answer is, No, you can’t—or at least you almost never can. Here’s why.

The cloth you see on the outside of a finished jacket is only part of the total material that went into making that coat. Inside, there is some excess, hidden between the outer shell (i.e., what you can see) and the lining. Most of that excess is what is called a “seam allowance.” It’s impossible, or at least very hard and quite pointless, to sew a stitch on the very edge of a panel of cloth. Thus when any two pieces are sewn together, the stitch is made a fraction of an inch from both edges. The excess is the seam allowance. It is folded back, pressed flat, and hidden inside the jacket, typically under the lining (assuming the coat has a lining).

Sometimes seam allowances are deliberately left very large to allow for later alterations. This is called “inlay.” The most typical place you find inlay is in the rear seam of trousers. Men being men, we tend to eat too much steak and drink too much beer, causing our waistlines to expand. When that happens, all is not lost, at least not sartorially. An alterations tailor, thanks to that inlay, can let our pants out at the waist.

But most seams don’t have a lot of inlay. Inlay, to a tailor or suit manufacturer, means extra cloth and hence extra cost.

What does this have to do with vents? Simple. A vent is nothing more than a long slit where a seam is left open and finished. For center vents, it is the jacket’s center back seam; for side vents, it is the two seams where the back panels of the jacket meet the side panels (or fronts, if the coat was made with wide front panels rather than separate side panels, called “sidebodies”).

To do make a vent, there has to be some excess cloth along the open seam. A vent is not like a simple snip, with two cut edges hanging in parallel. A vent needs to look closed at virtually all times. Trousers, belt and shirt are not supposed to show through, except perhaps in extreme poses. To achieve that, there has to be considerable overlap from one side of the vent to the other. And to get that overlap requires excess cloth in the right place.


The picture above (Figure A) is a pattern draft for the back panel of a center-vented jacket. The dotted line toward the right side, on the top half of the draft, is the stitch line. When the coat is done, everything to the left of that line will show. The small strip of cloth to the right is the seam allowance.

The other dotted line, the one that extends out to the right from the bottom half of the panel, is what makes a vent possible. On one side (the right side, looking at a center-vented coat from the back), that extra cloth will forum the underlap. On the left side, which overlaps the right side, it will be folded back under the panel and pressed flat. That way, there is a good two inches of overlap to ensure that the vent stays closed most of the time, or at least doesn’t allow things that shouldn’t peek through to be seen. When the wearer moves or puts his hand in his pockets, and the vent spreads open a little, the underlap ensures that observers mostly see jacket fabric—not shirt or belt or trouser.


Side vents are more prone to opening than center vents and require even more underlap. The second picture (Figure B) shows pattern drafts for a side-vented jacket. Note the large underlap area on the right panel (a sidebody panel).

The reason you can’t add vents to a ventless jacket is that, chances are, there is not enough extra cloth tucked away under the lining to create that overlap. Either the excess is built in from the beginning, at the cutting stage, or it isn’t. If it isn’t, it likely is not going to be there at all.

If you want vents on an unvented coat, you have two (very slim) hopes. First, it’s possible that the coat was cut with a lot of inlay. If it’s a bespoke jacket, that might be true; if ready-to-wear, it almost certainly isn’t. Even if there is inlay, it’s more likely to be along the center back seam than along the sides. And even if there is some along the sides, it’s not likely to be enough to create the necessary underlap.

Second, if your coat is simply too big for you, then it might be possible for a tailor to re-cut the backs to include vents. It won’t be cheap, however, and probably won’t be worth it. Better to buy clothing that fits in the first place—and which includes the vent configuration you want from the get-go.


A man of many nom de plumes, Manton is Nicholas Antongiavanni, author of The Suit: A Machiavellian Approach to Men's Style.