Piecing a backing for a longarm
 

I have always pieced my backings vertically, but I've heard that longarm quilters prefer a horizontally pieced back. Is this the case, and why is that?

I have usually left 5 in. on each side, of extra backing and batting. Does this need to be more for a longarm quilter? If I have already thread basted my quilt, will a longarm quilter be able to deal with that, or will I need to unbaste it?

A longarm quilter will not want to receive a quilt that has been basted. The three components (top, batting, and backing) should be completely separate. Generally 4" on each side is sufficient, and some longarmers are willing to work with 3" all around.

If a quilt back has vertical seams, these will build up in thickness when wrapped around the longarm rails. If the quilt is not very large, the buildup will be small and won't matter. Sometimes the quilt can be mounted at a 90 degree angle, so the seams will be horizontal rather than vertical, but that depends on the type of design being done.

Either horizontal seams or diagonal make the quilt much easier to quilt. Like Dunster said, vertical seams build up on the rails and can distort the quilt. I prefer diagonal because then no seam overlaps the other but horizontal works as well.

Thanks for your replies!

I've never heard of a diagonal back. Isn't stretching a problem? I'm trying (and failing) to picture how that would be done. Time for a tutorial search.

My Longarm lady prefers horizontal, like others have mentioned, because of the build-up.
Re the diagonal type join: John Flynn used to have instructions on his site how to do that, apparently it's useful when you are a bit short of fabric, but I haven't tried that method.

Here's a thread where we discussed the diagonal seam, has a picture and links to Flynn's calculation page.
https://www.quiltingboard.com/vbulle...p-t325542.html

This is best when you have a piece of fabric that is extra long, but not quite wide enough for your back. You cut on the diagonal and slide the pieces so you have a wider (but shorter) piece. Is cool geometry/area/math stuff :)

Talk with your long arm quilter for his or her preference for seam direction and extra all around. Sometimes I will note the top of my batting and backing with a tiny little note in the extra fabric that says "Top". Not required but it can save a little bit of time is if the width is nearly the same as the length. This is particularly helpful, so I hear, when the quilt is large. Less wrestling with back and batting. :)

I often make smaller quilts that are less than 50" wide -- that is where diagonal piecing comes into play. I use a cheat sheet from Jenny Breyer for the math. It lives on my desktop since I use it so often. https://jinnybeyer.com/wp-content/up...-Worksheet.pdf

It really depends on the longarmer. Mine doesn't care how I do the seams.

Is it acceptable to have just one horizontal seam in the middle of the back, or do I want to have two narrower pieces above and below a central wider piece?