Fabric made for outdoor use normally comes pretreated from the manufacturer with waterproofing and ultra violet protection. Indoor fabrics are not likely to have built in protection from the elements. This means indoors fabrics will decay from exposure to moisture and the colors will fade from sun exposure. If you find an indoor fabric that is the perfect design for your outdoor area, the fabric will need to be treated or it will not stand up to the sun and rain.
How to Turn Indoor Fabric Into Outdoor Fabric
Use the laundry soap, washing machine and dryer to clean the fabric. If the fabric is already applied to a surface, use a scrub brush wash with a bucket of laundry soap and water to clean the fabric surface. Let the fabric dry completely.
According to Trek7, a small test patch should be sprayed with waterproofing solution to test for colorfastness. Spray waterproofing evenly over the surface of the fabric.
Use the hair dryer on its hottest setting to warm the entire surface of the fabric. Make sure it is dry and repeat for maximum waterproofing protection.
Use the UV spray after waterproofing spray is completely dry. Spray the fabric evenly until the surface is moist. Let the UV spray dry completely.