Soffit is the material that covers the area beneath eaves, while fascia overhangs the roof rafters [source: Vinyl Siding Institute]. Before you begin installing vinyl soffit and fascia, be sure to do the following:

  • Read the instructions that come with the soffit and fascia.
  • Nail down any loose boards, panels, shingles or tiles.
  • Check that the undersides of the eaves are straight and even [source: Home Remodeling Technology].

To install the soffit:

  1. Nail an F-channel to the wall every 6 to 12 inches (15.2 to 30.5 centimeters), making sure the nails are centered within the channel's nail slots.
  2. Attach an F-channel to the bottom outer edge of the fascia board.
  3. Measure the distance between the channels. Subtract ¼ inch (6.4 millimeters) to allow for expansion.
  4. Cut the soffit panels to the measured size.
  5. Place the soffit panels in the channel slots so that the panels meet.
  6. Nail one T-channel or two ½-inch (12.7-millieter) J-channels between the panels for extra support.
  7. Attach F-channels or ½-inch (12.7-millieter) J-channels to the ends of each outermost soffit panel [source: Home Remodeling Technology].

To install the fascia:

  1. Measure the area to be covered by the fascia.
  2. Cut the fascia to size, if necessary.
  3. Punch a hole every 6 to 12 inches (15.2 to 30.5 centimeters) along the top surface of the fascia, using a snaplock punch.
  4. Insert the top of the fascia into the finishing trim with the bottom return leg covering the F-channel.
  5. Drill a hole every 24 to 36 inches (61 to 91.4 centimeters) through the fascia, F-channel and soffit groove, using a 3/16-inch bit. Then hammer a nail in each hole.
  6. Cut a piece of fascia cover 5.5 inches (14 centimeters) long. Skip this step if you have a corner cap.
  7. Mark a vertical center line on the back of the corner.
  8. Create a 90 degree cutout at the center of the bottom flange; each side of the cutout should be at a 45-degree angle.
  9. Fold the cover over the vertical center line with a hand seamer.
  10. Trim the ends of the cover at its corners.
  11. Punch the top edge of the corner cap with a snaplock punch.
  12. Hook the corner of the bottom ends of the fascia cover. Snap the top into place beneath the undersill trim lock [source: Home Remodeling Technology].