Questions for Long Armers.
 

I have finished my chicken quilt top, and am ready for the backing. I will need to piece it, which I've never done. When I'm done I want to have it professionally quilted. Which I've never done either. The shop lists this information: Provide at least 5" of backing and batting. Do not trim selveges, or square up the backing. We will do that for you. If you piece your backing, make sure you have pieced enough so that the selvege wording in not visible on right side of the quilt back. Iron your seams open." The quilt is 52 X 76. Does it matter which way the seams run? I know that the pieces should all run the same way...right? Any other tips or ideas? Always so much great info here.

Yes, you should have 5" or so on each side of the quilt, even more on the top and bottom. You can use a sheet if you prefer which you will not have to piece. If you have to piece, I would make the back in 3 pieces, going up and down.
Make sure the selvage is cut off the inside seams before you sew them or they may shrink and pull later on. Cut your one piece in two pieces. You could even make large pieces, like 20" or so. Good luck.

you are right having the pieces all run the same way. Your quilter will need to put the seam going horizontally so that it doesn't get saggy on the ends as she rolls it, risking puckers and tucks. you already know how much extra they want--make sure you have that much extra of batting if you are providing it too. On the selvages, if you don't cut them off where you piece (leave them on the sides that aren't the seamed part)you can snip every so often to allow for that uneven shrinkage--but I think it's easier to cut it off. Also--think about how you want it quilted--you will be happier with the result if the quilter knows what you are wanting and it will effect price too. You don't have to have it all worked out--that is part of the reason you are going to the LAQ--but know whether you want heavy quilting or just enough; geometic or all curves; Edge to Edge or perhaps an all-over with a separate border treatment, etc. also think about thread color--do you want it all one color or several different ones to match the fabrics. Lots to think about but also good questions for you and the LAQ to discuss.

Seams should run horizontal on the longarm frame. However, your quilt can usually be mounted "sideways" to make the seams run horizontally. The exception to this would be if the quilting pattern is directional. I'm surprised that this longarmer wants the seams ironed open. I think they're stronger when ironed to the side, and certainly less chance of batting poking through. It's also not clear to me whether the longarmer wants 5" all around, which is on the high side, or just 5" longer than the quilt top, which is on the low side. Usually 3-4 inches all around is more than sufficient, but if the longarmer intends to trim the backing that may be the reason for asking for 5".

Seams need to be horizontal so the lay flat across the roller bars. If they are vertical they will build up bulk as the quilt is turned on the frame causing floppy sides. The 5" is all the way around, so 62"x86" or larger for your 52"x76" top.

You will need to check with your longarm person to see which direction they prefer the seam to run.

Some people want it to run vertical (top to bottom) and some want it to run horizontal (side to side).
I prefer horizontal, myself.

As far as the "extra fabric" goes... you will probably 5" ON EACH SIDE... so that means 10" total. This gives the longarmer room to attach the top and bottom edges to their leader, as well as having something to clamp on the sides.

I have a long arm and didn't give a lot of thought as to how the seams should run on a pieced backing, until I pieced one vertical. As I quilted, there grew to be a mound in the middle of my frame and the sides of the quilt were slightly slack. I ended up having to work and pull different sections of the sides as I quilted them to avoid puckers and little darts. Now, I make sure the backing seam is either on the diagonal or horizontal to the quilt.

If I have to piece the back, I do my backing seam as 1/2" and I do iron it open. I have not had any problems with batting pulling through. I do use a 1.8 or 2.0 as my stitch length.

For the backing and batting, I do add 10" to the overall width and the same to the length of the quilt to allow for positioning the quilt properly and for a practice sewing area when I have to change the bobbin. My older Nolting can be a challenge if I don't do this. It tries to forget everything it knows about sewing if I don't do a few stiches on the edge to make sure the mind is still there. Mostly it is my fault, because I don't always get the bobbins wound just right. I've learned to check them over very carefully.

Thank you all for your replies. I called the shop, and asked about piecing, and she told me that it didn't matter which way the seams ran, as long as I have the extra 5" on all sides. Think I'll go horizontal to be safe!