When the fabric on a favourite piece of outdoor furniture wears out, or is torn or stained, but the furniture itself is still in great shape, it makes sense to replace the fabric. However, outdoor furniture must withstand punishing weather, and so only speciality outdoor fabric is appropriate.
What to Look For
Before you begin to shop, get a fabric sample to bring with you. If the patio swing has matching cushions, they will work. Otherwise, consider cutting out a section of the old cushion-covering fabric. Cut a square from the underside of the cushion, as it is less likely to be faded. It's unlikely, though not impossible, to find an exact match for the original fabric used by the manufacturer, but you'll need a fabric swatch to verify a perfect match if you think you've found one. The swatch will also help you choose a coordinating fabric should your swing have an intact fabric awning or other fabric components.
Outdoor furniture requires upholstery that will hold up to the elements, so most fashion fabrics won't work well. Standard fabric stores, however, stock a limited stock of upholstery fabric, and you'll likely find that the selection of outdoor upholstery fabric is even more limited, if they have any at all.
Find a Store
To find the best selection, and increase your chances of finding a bolt of remainder fabric of the exact fabric you need, shop for your fabric at a fabric liquidator's store. Usually, these stores are called fabric warehouses. Often, the warehouses are in industrial parks and office parks, rather than in malls or other retail areas of a city. You'll know you've located a true fabric warehouse if they use 'wholesale' in their ads or listings.
Fabric warehouses are enormous, and they generally have few sales people available to assist customers. Ask for help finding the outdoor upholstery fabric; nearly always, they'll have all of them in the same area. But don't expect extensive assistance in locating specific fabrics. However, do ask the sales person if they recognise your fabric. They might not be able to tell you exactly where it is, but may tell you if it's likely to be found amongst the bolts of fabric in their collection.
Find the Fabric
Allow at least a couple of hours to dig through the fabric selections, and wear comfortable, machine-washable clothes. Although warehouses are generally clean, they are nonetheless warehouses, so you may brush up against dusty surfaces while shopping. In any case, you'll be moving 10-foot-tall rolls of fabric to see what's behind them. Bring a friend to help you search. When you find your choice of fabric, ask warehouse staff to help you extract a bolt or roll.