Replacing fabric for a round patio umbrella involves measuring and calculating the fabric yardage. Purchase the widest exterior waterproof canvas, polyester or nylon fabric you can find to minimise seams. Fabric stores sell 54-inch and 60-inch fabric widths. Use waterproof fabric intended for outdoor use to eliminate rapid deterioration of the umbrella. You may have to sew several lengths of fabric together and then cut out your umbrella using the old round umbrella as a pattern.
Open the umbrella. Leave the current umbrella intact for measuring.
Measure the umbrella's width from the left side up over the umbrella to the right side. Add 4 inches for seam allowances. This is the modified width.
Measure from the umbrella's centre bottom edge up over the umbrella to the "point" of the umbrella. The point is called a ferule. Your umbrella may have a finial over the ferule. Add 4 inches. Multiply this measurement by 2 to find the modified length.
Purchase fabric according to the modified width and modified length. You might have to sew two or more lengths of fabric to achieve the necessary width. According to the Patio Umbrellas website, a 48-inch diameter table should have a 9-foot diameter umbrella.
Remove the old umbrella from the frame. Draw a diagram of the umbrella construction. Include any hardware, grommets, holes around the ferule or eyelets and label each part for reference.
Use a seam ripper to remove the stitches from the umbrella. If making a panelled umbrella, remove only one panel if panels are identical. If the umbrella is one piece, remove all of the stitching. Save any hardware to reuse.
Place the panel or umbrella onto an ironing board. Iron the seams open and flat. You will use the old umbrella as a pattern.
Prepare fabric as necessary. If your single-piece umbrella is wider than the fabric purchased, sew two or more lengths of fabric to achieve the width necessary.
Pin the pattern (old umbrella) to the new fabric. Cut out the umbrella or umbrella pieces. For a panelled umbrella, cut out the number of panels present on the old umbrella. Most panelled umbrellas have between four and six panels. Remove pattern from new fabric.
Pin the panels together or form the hem by folding the edges under 1/2 inch, and then under 1/2 inch again. Pin.
Sew the panels together using a straight seam. Examine the old umbrella to determine the seam allowance used or use a 1/2-inch to 1-inch seam allowance. Remove pins. According to the Sewing and Craft Alliance, use a 70/10 or 110/18 needle. These needles are very sharp and strong and can handle thick fabric without snapping. If there are no panels, skip to Section 3 Step 5.
Sew the hem (for a panelled umbrella, follow hem instructions in Section 3 Step 3) using a straight stitch and 1-inch seam allowance. Remove pins.
Topstitch seams and the hem. A topstitch is visible stitching sewn on top of the umbrella over the seams for reinforcement.
Replace any hardware. Refer to your diagram for correct placement. Attach the umbrella to the ribs of the frame by hand sewing with a needle and heavy-duty nylon thread through the holes in the ribs and through the umbrella fabric. Or, replicate the attachment of the original umbrella. According to Umbrella Recovery, an umbrella has six to 12 ribs.
When in doubt, err on the side of too much fabric rather than not enough. Save excess fabric for future umbrella repairs.