How to Build a Fascia

Trim rafter tails vertically to create the surfaces to which you'll attach the fascia boards. The length of rafter overhang depends on several factors, including the style of the building and whether your roof design includes soffits. To trim rafter tails evenly, place a two-by-one square against the house wall and measure out to the edge of the rafter. You can also do it using a measuring tape and a carpenter's level. Measure down the wall as low as you want the overhang to come, then use the level to mark the bottoms of the rafter tails at the bottom of the desired overhang. Run a chalk line from one end of a course of rafters to the other, both bottom and top. Run the line over and under smaller groups of rafters that make up a long roof span. Snap the line to mark the bottom of the cut you will make on each rafter. Leave the chalk line in place.

Use the two-by-one square or the combination of measuring tape and level to determine the top cut needed to make a consistent vertical cut in all the rafter tails. Use a plumb bob and line to verify the vertical cut marks are correct before chalking and snapping the chalk line. Fascia is effective only when well-fitted; "measure twice and cut once" even if you're using trusses with a factory-made vertical cut, to ensure a good installation.

Install a subfascia board by nailing or screwing it to the cut ends of the rafter tails. An informal survey of handyman and do-it-yourself websites suggests that a subfascia is most often used when the roof design includes soffits, although not always. The same survey suggests that there is no absolute agreement on the width of either subfascia or fascia boards; a 2-inch thickness appears common, but board width can vary generally from 4 to 6 inches for subfascia and 6 to 10 inches for fascia. If you are using subfascia, attach it securely, using a minimum of two screws or nails per rafter tail and preferably four.

Miter the ends of fascia boards if your roof design requires it. You can butt fascia against rake-board, but a house with corners and angles in the roof will require mitering fascia boards for the best fit. Attach the fascia board to the rafter tails in the same way, whether you are installing it over subfascia or not. Fascia board should be positioned so that there is no space between it and the tops of the rafter tails. Your fascias are now ready for supporting soffits, painting and installing gutters.