PM/GC Quilts Skill Builder Series: Part 16 – Y Seams

For some reason, I’ve always been a little afraid of Y seams, but they really aren’t all that awful. A Y seam is exactly what the letter looks like – a place where three seam lines intersect. Believe it or not, Y seams are actually quite easy if you hand piece. They really aren’t much different than a regular seam. To machine piecers it seems more difficult because we are accustomed to just pushing the fabric through the machine, trusting that our quarter inch foot or guide will line up the seams correctly. Everything is flat when it goes through the machine on “regular” seams, but with Y seams you need to fold fabric to get the excess out of the way before sewing.

Some quilter have had success breaking blocks with Y seams into smaller components, piecing half square triangles so the same fabrics are next to one another. This gives the same appearance as a Y seam, but with an easier construction technique. The well-loved Swoon quilt pattern by Camille Roskelly (pattern available from her shop, Thimble Blossoms) is very similar to an old block called Star of Bethlehem, circa 1931 from Prize Winning Designs (Quilter’s Album of Patchwork Patterns, page 289):

There are some slight changes in color placement and she removed the corner triangles, but the biggest difference is that some of the shapes have been changed slightly so they can be cut in half and pieced as half square triangles and flying geese. To illustrate the slight difference in shapes, here are the two blocks side by side. On the left is the Star of Bethlehem block recolored to match the Swoon layout. On the right is the Swoon block. Both blocks are shown without seam lines.

Star of Bethlehem block recolored Swoon block

If you look closely, the blue house shapes in the four corners of the Swoon block are narrower than the ones at the top/bottom/left/right. Also, the pink diamonds aren’t exactly diamonds, and the center star is a slightly different shape, with the points coming in farther and the white triangles between the points being slightly different sizes. The difference is very subtle, and both blocks are beautiful. This is a great way to make a complex block more accessible. But, you know, this post is about Y seams…

Y seams are used in a lot of 8-pointed star blocks like the Star of Bethlehem, LeMoyne Star, Carpenter’s Wheel, Lone Star and Feathered Stars.

LeMoyne Star
Carpenter’s Wheel
Lone Star
Feathered Star

They’re also used in the optical illusion called Tumbling Blocks:

Tumbling Blocks

And of course, the hexagon and it’s many variations, including those created with diamonds and triangles:

Pieced Diamonds Hexagon

Quilts that have an overall pattern that can’t be broken down into squares or rectangles all use Y seams. One of my favorites is a design called Jack’s Chain or Rosalia Flower Garden, made of nine patches, triangles and hexagons. This is a challenge to draw in EQ7, and I wasn’t having much luck. Fortunately, Marjorie at Quilt Design NW is smarter than I am, and shared an EQ7 file for the pattern. Here is my colored variation:

Jack’s Chain

I even found this design requiring Y seams on a tissue box! Wouldn’t it make a great quilt?

Tissue Box quilt


The example I’m using is my LeMoyne Star block from the Test Your Skills Sampler. The TYSS post will follow this one within a few hours, and will contain the complete cutting and piecing instructions for a 12″ finished LeMoyne Star. This post will focus only on the Y seam.

There are two tricks to Y seams. The first trick is knowing exactly where the seam line is. Oh, obviously it’s 1/4″ from the edge of the fabric, but with the long points of a diamond, there’s a little extra fabric. Most instructions for Y seams have you put a dot at each corner indicating where you should start and stop sewing.

LeMoyne 23

You may find it even easier if you draw the complete sewing line on the back of the fabric. This way you can see exactly where the lines intersect. This is especially true when working with non-90 degree angles (anything other than squares or rectangles).

LeMoyne 10

Second, you don’t sew from edge to edge – instead, you sew from seam to seam. In other words, you start sewing where your seam line intersects with the adjacent seam line, and stop when you meet the next seam. If you marked your starting and ending points with a dot, place your fabric under the presser foot and drop the needle through that dot, then sew to the ending dot.

LeMoyne 27

If you marked complete seam lines, drop you needle where they intersect and sew to the next intersection.

LeMoyne 18

One part of sewing Y seams that confounds people is how to get the fabric you’ve already sewn out of the way. Be patient. Slow down and just ease the fabric to where it needs to be. Try not to sew over any seam allowances, since that will make it easier to press the seams later.

The first two thirds of the Y seam are easy. It’s that last one that requires fabric to be folded out of the way. In the example below, I’ve already sewn the yellow and green fabrics together, and the blue to the green at the left. Now I need to get that second blue edge right sides together with the yellow edge.

LeMoyne 16

First, I flipped the blue fabric up and folded the green and yellow fabrics so they were right sides together.

LeMoyne 17a

Next I pulled the blue point down and to the right so it lined up with the yellow point. I pinched the blue/green seam and pulled it to the left as the blue point came down.

LeMoyne 17b

You can see in this last photo that the green fabric is folded between the layers.
LeMoyne 17c

All that’s left is to sew the last seam from point (seam intersection) to point (seam intersection). Drop the needle through the dot or seam intersection, then put the presser foot down. It is important here that you are only going through two layers of fabric, NOT the fabric that is folded out of the way. If you can manually roll the needle down, you can feel more resistance if there is extra fabric. This is one time when an automatic needle up/down button works against you. Sew to the next intersection.

LeMoyne 18

Y seams can be bulky, so one way to reduce that bulk is to spiral press, “splitting” the seams where they intersect. As long as you did not sew to the edge of the fabric, this is easy. Just press each seam from the intersecting point to the edge. Each one should go in the same direction, as if you pressed in a circle. Once the main seams are pressed, you can press the center, which has a tiny bit of the right sides of each fabric exposed.

LeMoyne 19

Well, that’s how you do a Y seam! Any questions? Any tips that you’d like to share if you’ve had some experience with Y seams?



  1. Another wonderful post! And wonderful choices of quilts and quick blocks, too.

    I have never sewn a Y-seam but I stumbled across this nifty trick for piecing the seams in hexagons: If the link doesn’t work. I found it on YouTube, posted by Heirloom Creations under “Grandmother’s Flower Garden.”

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