How to Replace Rotten Wood Column Base Trim Boards

Porch column base with new unpainted pressure treated base trim boards..
Trim boards on column base after replacing.

The boards around the base of a square wooden column can become damaged or rotten over time due to exposure to the elements. Here’s how to remove and replace them.

How to Replace Column Base Boards:

  1. Remove Old Base Boards: Use a hammer and pry bar to remove the damaged boards around the column base.
  2. Cut New Column Base Boards: Cut new pieces to match from pressure treated or rot resistant wood, mitering the corners at a 45° angle on a miter saw.
  3. Trial Fit Boards to Column Base: Test fit the pieces around the column to make sure the joints are tight.
  4. Nail Boards to Column: Attach the new base boards to the column using corrosion resistant (galvanized or stainless steel) finishing nails.
  5. Cut and Attach Cove Molding: Miter cove molding to fit around the top of the boards, and attach it with finishing nails.
  6. Caulk Column Base: Caulk the nail holes and corner joints using a quality exterior acrylic latex caulk.
  7. Paint Column Base: Prime and paint the new boards with quality exterior paint.

Watch this video to find out more.

Further Information

Danny Lipford: While the base boards around outdoor columns are strictly ornamental, they are also the most easily damaged by moisture.

Now, remove the old boards with a hammer or pry bar, and cut new ones from pressure treated lumber matching the old dimensions. You’ll need a miter saw to make the two inward facing 45-degree cuts on each piece.

When all four pieces are cut, dry fit them in place to be sure the joints are tight before attaching them with finish nails. Smaller finishing nails can be used through the corners for extra security.

This column had a cove detail around the top, so we’re replicating that with four mitered pieces of cove molding in the same profile. When everything is in place, seal all the seams with caulk to prepare for painting.


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