Drapery Fabric for Upholstery?

Generally decorating fabrics come in at least three varieties, Drapery, multipurpose (which can be used for either drapery or upholstery, and upholstery. For this article I'm focusing primarily upon the idea of using drapery specific fabrics (such as shiny polyester and rayon) for upholstery. 

Drapery Fabric Is Not Meant For Upholstery
Here are some of the reasons I don't recommend doing a job in lightweight drapery fabric.

1. The fabric was not constructed for upholstery use. It is not meant to have hundreds of pounds of human weight sitting on it. Rather, it is meant to hang lightly on the window.
2. Most lightweight drapery fabrics don't have enough body (thickness and stiffness) to be able to evenly pull the fabric. It is difficult to pull the fabric evenly enough to have a smooth stapled edge.
3. The fabric usually has a lot of little pull marks at every staple (no matter how many staples you put in)
4. Some areas of the upholstery cover require that you pull the fabric tightly, thereby putting a lot of stress on the fabric. This can cause some of the seams to rip loose.
5. Since the fabric doesn't have an upholstery backing, the seams can sometimes easily unravel.
6. With such a thin AND a shiny fabric, many little bumps (cotton seeds, etc.) show through the fabric.
7. Since the drapery fabric has a weaker thread weave, the fabric is likely to have a very short lifespan.

With that said, sometimes, if you are very careful, some jobs can turn out tollerable. But it's a matter of doing an awful lot of extra work (that you don't get paid for) to have the job turn out mediocre at best.

If you feel that you must
 With that said, if you are dead set on using smooth and shiny polyester or rayon type fabrics for upholstery (which I don't recommend), here are a few suggestions.

1. I would STRONGLY suggest that you require the client to provide you with ample EXTRA fabric to practice on.
2. I'd STRONGLY recommend that you cover the furniture in an undercover using muslin or lining fabric before covering it with the drapery fabric. The undercover will take a lot of the stress instead of the stress going to the covering fabric. The lining will also help to minimize the staple pull marks.
3. Using some of that extra fabric, I'd suggest that you do some practicing and make an upholstery prototype.
4. Make sure you use a new needle when you sew the fabric. Use a very small sized needle. The big upholstery needles can catch the thread and pull the weave of the fabric causing runs in the fabric.
5. Use a smaller weight of thread.
6. Be open and honest with the client before you start, telling about the challenges of working with drapery fabric. (puckering seams, pull marks at each place you staple, etc.) Put these explanations and disclaimers in the contract.
7. I might suggest that you use a regular straight-stitch sewing machine (or a home sewing machine) with a zipper foot. The walking foot sometimes doesn't work very well on such thin fabrics.
8. Use a fray reducing product, such as Sprayway No Fray Spray (which you can probably get from your supplier), along the outside edges of the backside of the fabric. Test it on a scrap first to make sure that there is no staining or bleedthrough. If it doesn't bleed through, spray it on the backside and let it thoroughly dry before sewing. I use this product on any fabric that might unravel, or that is very flimsy. Besides helping to minimize fraying, it also gives the edges of the fabric a little more body so that it is easier to sew.
9. If you will be stapling this fabric, turn down the pressure on your air compressor when you are stapling the drapery fabric. It is very easy for the staples to go right through the thin drapery fabric.
10. OR cover the furniture or cushion in lining first before covering it in the drapery fabric.