Porch flooring is exposed to the elements, so over time even the most durable types will become damaged. The flooring may begin to rot, which can cause major damage to the porch if the rot spreads to the joists. Damaged joists are more difficult to replace than flooring, so flooring damage should be fixed promptly. Do not simply cut out the damaged areas and patch the floor; this creates joint lines that look out of place in an otherwise jointless porch. Use full-length flooring boards to preserve the look of the porch.
Remove the Damaged Flooring
Remove the first damaged board by running a circular saw or rotary tool with a multipurpose cutting bit down the center of the board. Set the depth of the saw by holding the saw up to the board on an edge and set the blade so that it is level with the bottom of the board. This will prevent you from cutting into flooring joists.
Stop the circular saw or rotary tool before you reach the wall of your house. Use a 1-inch demolition chisel to split the remaining part of the board.
Remove the board with a pry bar and hammer. Be careful not to damage nearby boards if they do not need to be replaced.
Pry up the next damaged board using the pry bar. Start at the edge of the porch and work toward the house until the board pops loose. Remove any nails that stay in the joists.
Continue removing all damaged boards in this manner. You only need to cut a board in half if it has no neighbor that has been removed.
Scrape the grooves and tongues of the exposed boards with a 5-in-1 scraping tool, or use an oscillating tool with a sanding or scraping accessory.
Replace the Flooring
Purchase new flooring that matches the dimensions of the existing porch flooring. If you cannot find an exact match, choose larger boards and have a carpenter mill them down to size for you or do it yourself on a table saw.
Prime all edges and faces of the new boards with an oil-based primer to protect them from moisture.
Squeeze construction adhesive on the exposed joists and place the first board, matching the groove of the new board to the tongue of the old board. Nail the board with a ring-shark sliding nail at an angle through the tongue into each joist. Recess each nail with a nailset.
Install the remaining pieces until you reach the board that will be next to old flooring. Mark the position of each joist on the adjoining board. With a table saw, cut off the bottom part of the groove so that it will sit on top of the tongue of the old flooring.
Slide the tongue of the last piece into the groove of the old flooring and tap the board into place until it sits firmly on top of the tongue of the previous piece. Place a sliding nail at each joist vertically instead of at an angle. Recess the nails using a nailset.
Sand the patched area so that it is flush with the old flooring. Paint the new decking to match the old.