Why do knits gape?
First, let’s talk about the why.
On a woven garment, bust darts (or sometimes princess seams) allow for the fullness of the bust. Essentially, they create a cupped shape around the bust area. That means there’s extra room at the apex, but not the armhole or side seams.
Here’s an example: The Seamwork Adelaide. The dart helps cup the bust.
Knits typically do not have bust darts. Instead, they rely on the cut of the outer edges along with the stretch of the fabric itself to accommodate the bust.
This means that a lot rides on your fabric and how it responds to stretch and handling while it’s sewn. For fitted knit dresses without sleeves, if your fabric doesn’t have excellent recovery, or if it gets a bit stretched out when being sewn, you can get extra fullness around the arm opening.
Here’s the Wren in a cotton French terry without a lot of recovery. You can see that it’s gaping a bit at the curve of the armhole.
The larger your bust is, the more you might notice this problem with sleeveless fitted knits.
Luckily, this is easy to check, fit, and fix as you’re sewing. So let’s fix it!
Check the fit
First of all, check the fit as you’re sewing a fitted sleeveless knit garment. After you’ve sewn the shoulder and side seams, but before finishing the armholes, try it on.
Notice if you’ve got a bit of extra fabric forming a little fold that radiates from your bust apex.
Pinch it out, pin it, and measure. Now you have several options to reduce this fullness.
Option 1: Add a dart
This is the simplest way to get rid of gaping.
Pinch the fold on the wrong side of the fabric and sew into a dart, using a stretch stitch such as a narrow zigzag.
- Really easy to do.
- Gives a tailored fit.
- Works great on stable knits, like ponte.
- Changes the style lines slightly.
- Stitches can be prone to popping.
Option 2: Add a band or binding
Usually with knits, the alternative to adding a dart is easing extra fabric in.
This is easy to do if you finish your armholes with a band or binding rather than a dart.
Measure the dart you pinched out. Mark the armhole about one inch past this.
Cut your band or binding so that it’s at least that much smaller than the armhole. For this example, the little dart I pinched out was 1 inch. I cut my band 2 inches smaller than the armhole. It turned out perfect.
When you sew on the binding (or band), ease between the underarm seam and the marking by stretching the binding to fit that area. I stretched the binding gently all around this armhole, but stretched it to the maximum around the curved area, where it needs the ease.
This will bring the armhole in to hug the underarm while still allowing for that needed fullness around the bust.
See our ultimate guide to knit edges if you want to learn how to install either a band or binding. I really like the band. This is my favorite alternate way to finish an armhole that gapes. It’s easy and turns out clean and fitted!
- Looks very tidy.
- Easy to do with a little practice.
- Gives a really good, smooth fit.
- Slightly more work than sewing a dart.
Option 3: Elastic edges
One more way to finish your armhole and prevent gaping is to use elastic.
Again, cut the elastic smaller than the armhole and ease through the area you marked around the pinched-out dart.
For this, you can use a decorative lingerie elastic, or try fold-over elastic. The important thing is to ease (stretch the elastic as you sew) around the area where you’re experiencing gaping.
- Looks professional.
- Highly elastic and durable.
- Decorative elastic can add an ornamental twist.
- Requires purchase of elastic.
- Can change the look, especially if you can’t find elastic in an exact match.
- Slightly more work than sewing a dart.
If you need help sewing lingerie elastic, check out our tutorial on sewing lingerie elastic 3 ways.
All three of these methods are great alternate finishes to use any time you find your knit gaping. It works for other areas like necklines too!
You can pick up patterns like Wren to try this out, and you might also like The Colette Guide to Sewing Knits if you want even more handy tips like this. Better yet, save some money and get them as a bundle with another pattern!