How to Build a Soffit
Soffits can be used to cover unsightly features of a home or to add decorative architectural detail.
Measure the depth of your knee wall. Cut a piece of 1x8 pine to this length plus 4 1/2 inches. For example, if your knee wall measures 11 1/2 inches, make your cut at 16 inches. This piece will serve as a base for the column.
Using a router with an ogee bit, router the edges of the base piece. Leave one of the short edges un-routered.
Measure the width of the knee wall. Using a jigsaw, cut a rectangular piece out of the base. The rectangle should be 2 1/4 inches deep and as long as the width of the knee wall.
Put the pillar base on the knee wall and make sure it's level (Image 1). Use shims to correct the level, if necessary. Remove the base and apply construction adhesive to the knee wall. Re-insert the base and re-shim, if necessary. Nail the base into place using the nail gun (Image 2).
Measure for the height of the columns.
Set the table saw to a 45-degree angle. Rip the 1x6 pine boards down each side of all four boards.
Cut two square blocks of wood that will fit into the interior of the column. This will be the extra support to hold the four sides of the column together. Lay one of the ripped 1x6 pieces face down. Put a square interior block on top of the end of the 1x6 piece. Measure out to the height of the column, and place the second square block at that measurement. Put another piece of ripped 1x6 on top of the two square blocks. Use a speed square to make sure the interior blocks are square (Image 1). Nail the top 1x6 piece into the interior square (Image 2).
Apply wood glue to a 45-degree edge of one of the 1x6s. Line up the edge of another piece of ripped 1x6 to the glued edge. Flush up the two pieces, then attach using the nail gun. Continue this process for the final two pieces.
Mark the column at its intended length (Image 1). Using a speed square, mark this length off on all four sides of the column. Using a circular saw or chop saw, cut through the column one side at a time (Image 2).
Place column on base (Image 1). Make sure it's level, and shim it, if necessary (Image 2). Toenail it into place using 16-gauge nails (Image 3). Apply crown molding to the top, if desired, and stain or paint.