Ask A Longarmer: Should I sew a horizontal or vertical backing seam? 

People often ask me if their backing seam should run horizontally or vertically. The answer to this question is quite simple: it depends. ?

In an ideal world, every quilt that I loaded on my longarm frame would have a backing seam that was parallel to the rollers of my machine. Kind of like this…

Why does it matter?

For a few reasons! First, there is more tension between the rollers than there is from side to side. When quilt backings are loaded on the frame, they’re being pulled (a little, not a lot) between the bars. This helps keep the backings nice and flat, so that you get the best longarm quilting results.

When the backing seam is parallel to the bars, the tension is distributed evenly across the entire seam, which keeps the fabric on either side of the seam flat as well.

When a quilt is loaded with the backing seam perpendicular to the longarm frame, it looks like this:

What’s the problem with a perpendicular seam?

When you sew a seam, it changes the elasticity of a fabric. Normal quilting cotton has between 5 – 10% stretch if pulled on-grain (not very much, and not very noticeable). If I loaded one continuous piece of quilting cotton on my longarm frame and tightened it between the rollers, there would be a bit of stretch (again, not very much).

But if I sliced that fabric into two pieces, sewed it back together, and then loaded it with the seam perpendicular to the bars, there would be practically NO stretch at the seam. BUT, the rest of the cotton would still have a bit of drape, so it would be more loose towards the edges.

This might not be a big deal if the entire backing was cut and pieced perfectly square (which is nearly impossible to do), was made from cotton, or was fairly small. In that case, the difference between the perpendicular seam and the sides might not be significant and the backing would lay pretty flat. Huzzah! That’s great for longarming results!

BUT, if the backing was large, or was made from Minky (a highly stretchy fabric), and had a perpendicular seam, there might be SIGNIFICANT droop at one or both of the sides. Kind of like this:

This… is… not ideal.

It’s hard to get that droopy bit to lay flat so that the longarm stitches are even and don’t cause any puckers in the backing fabric.

Also? That perpendicular seam is quite thick. It gets rolled up on the bar over and over again, which results in a big fat lump on the take-up roller. That affects the way the rest of the quilt is rolled up, and can cause the quilt top to become uneven. So in short, if I’m working with a pieced Minky backing, I’m *really* hoping that I can load it with the seam parallel to the longarm frame.

So with all that in mind, should all backing seams be pieced horizontally? Not necessarily!

And just so we’re really clear, here’s what I mean about a horizontal vs vertical seam. Imagine I was piecing the backing for this Checkered Garden quilt.

This is what a horizontal seam would look like (it would be running from side to side across the quilt top).

And here’s what it would look like if I pieced my backing fabric with a vertical seam (it would be running from the top to the bottom of the quilt top).

Pantograph directionality

When deciding which way to sew your backing seam, you might also want to consider what kind of pantograph will be stitched on the quilt. Maybe you’ve thought about this before, and maybe you haven’t, but pantographs have a direction to them. Whaaa?

If a pantograph is vertically-oriented, the longarmer needs to load the quilt top upright (in the normal direction) in order to achieve the desired look of the pantograph. Like this example using the Wishbone pantograph:

If you’re going to be using a vertically-oriented pantograph, a horizontal backing seam is ideal (because it will be parallel to the longarm rollers).

If a pantograph is horizontally-oriented, the longarmer needs to turn the whole shebang (backing, batting, and quilt top) sideways in order to achieve the desired look. For example, the 60’s Mod pantograph is often advertised / shown with the “vine” running up and down. However, most clients want the vines to run from the top to the bottom of their quilt. In order to achieve that, the longarmer turns everything sideways. Like this:

If you’re going to be using a horizontally-oriented pantograph, a vertical backing seam is ideal (because it will be parallel to the longarm rollers).

And some pantographs are omni-directional. That means that they look the same (or very close to the same) whether the quilt is loaded upright or sideways. Soho is one of my favourite pantographs because of its versatility when it comes to loading direction.

When your’e using an omni-directional pantograph, a horizontal or vertical backing seam will work equally well.

What if I haven’t decided on a pantograph when I sew the backing seam?

Look, I get it…. Not everyone spends their days thinking about the direction of pantographs and seams. And I would assume that you probably sew your backing seam way before you decide what panto you want. So how should you sew your backing seam?

Just do whatever is easiest / least expensive.

I mean, *ideally* all quilts would be loaded with a seam parallel to the longarm rollers, but I load quilts with a perpendicular seam… all… the… time. Like, every day. It’s my job to make it work!

So don’t worry if you sew a seam in a certain direction based on the amount of backing fabric you have on hand, and then choose a panto that requires the longarm quilter to end up with a backing seam that runs perpendicular to the rollers. It’s fine. Promise.

And d’you want to know a secret? If a client sends me a quilt and has not decided on the panto they want, I’ll often make a suggestion based on a) the quilt pattern design, and b) the direction of their backing seam. If they’ve sewn a horizontal seam, I’ll normally suggest a vertically-oriented panto, and vice versa. Whenever possible, I want that seam to be parallel to the bars! As a quick aside: if you want to see how I choose how to size a pantograph, you can check out this blog post.

And yes, it has happened that a backing has too much sagging when loaded with a perpendicular seam, and I have suggested a different approach to my client. That’s a case where the trust and communication between longarmer and client is crucial!

How did I do?

Did I answer all of your questions about the direction of your backing seam? If I’ve missed something, please pop your question in the comment box below and I’ll answer it for you!

And if you’d like me to longarm your quilt for you (no matter which direction your backing seam runs), you can read more about my process here, or sign up a quilt here.

Wishing you happy seaming!!