With a little hard work and planning, you can fix an old or rotten porch and make it look new. Porches are typically made from either wood planking or concrete over a wooden frame, depending on when your home was built. If your porch floor is rotting, sagging or warping or the concrete is cracking, it probably needs repairing. Signs of rotting can include board discoloration or crumbling. If your porch is just beginning to show a little wear, a quick coat of sealant may fix the problem.
Repair a Wood Porch
Cut out the entire porch board or boards that need replacing. Use a circular saw to cut through the board, keeping the edge of the blade flush with the porch joist. This will keep you from cutting through the actual joist. Starting at the end farthest from the house, cut the plank to be removed down the middle to avoid hitting any nails. Continue until you reach the edge of the board or the porch joist at the exterior edge of the porch. Do not cut through the porch joist.
Pry the rotted or damaged wood porch planks loose gently using a crowbar, starting with the one you've cut. Remove all damaged boards.
Measure the length of your porch from the exterior of your home to the edge of the porch to figure out the length of each new porch plank. If one of the old porch planks you removed is still intact, measure it to get the correct length for your new planks. Cut the planks to the correct length using a circular saw.
Paint the new plank boards with an oil-based deck primer to protect them from moisture. Let the boards dry.
Install the new boards. Apply a bead of polyurethane construction adhesive on the top of each of the porch joists. Using a hammer, tap each board into position, until it's flush with the board next to it. If you prefer, you can hammer nails through the porch floor planks into the porch joists every 4 to 6 inches to hold the boards in place, instead of using adhesive.
Trim the outside end of your porch boards with the circular saw if you have an uneven porch edge. Use a ruler or other straight edge and a pencil to mark the intended edge. Cut the boards flush with the mark or the edge of the existing boards using the circular saw. Once you make the initial cut, keep the edge or side of the circular saw blade flush with the edge of porch to help keep the saw balanced.
Use a hand sander or a belt sander, depending on the size of the spot you repaired, to sand the boards flush with the old boards. Sweep away or vacuum up any sawdust.
Wipe the boards down to make sure you get any last particles of sawdust. Apply a coat of oil-based primer to the ends of any boards you cut earlier that are still exposed. Let the paint dry. Apply a coat or two of deck paint to the whole porch.
Repair a Concrete Porch
Brush and scrape away any loose concrete, paint flakes or other items with a wire brush and a basic paint scraper. Inspect the porch for any gaps or holes as you work.
Fill any noticeable leaks or cracks with concrete caulk or sealer. You can typically use concrete caulk to fill smaller cracks less than 1/2 inch wide. Cracks larger than a half an inch or holes usually will need to be filled with a concrete patching compound. Apply any patching compound using a concrete or cement trowel.
Fill large holes or problem areas in the steps or porch floor surface with a quick-drying, self-leveling concrete patching compound. Use a cement or concrete trowel to even the self-leveling compound if it appears uneven. Let the patches dry and cure for at least a week.
Apply two coats of exterior porch or deck paint to help seal the concrete and protect it from moisture.