Watch this video from This Old House to learn how to replace your exterior columns.
1. Cut cedar to width and length to create proper size column.
2. Apply two coats of exterior-grade primer to the interior surfaces of the boards.
3. Join together the cedar boards to form a square column using waterproof glue, wood biscuits, and 6d galvanized finishing nails.
4. Clamp a wood stop block to each end of the column.
5. Attach homemade indexing base plate to router.
6. Rout six evenly spaced flutes into all four sides of the column.
7. Lightly sand the column.
8. Attach redwood caps to each end of the column.
9. Add decorative trim around the column near each redwood cap.
10. Set the column into position, standing it on top of a square of builder's felt.
11. Plumb column with a 4-foot level, then fasten it with 10d finishing nails.
12. Use a utility knife to trim away the excess builder's felt from around the base of the column.
13. Cut and install base molding around the bottom of the column.
14. Prime and paint the column.