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A damaged porch floor can be more than just an eyesore. It also poses a tripping hazard and can lead to further structural issues if left in place. Luckily, it’s an easy fix, and This Old House general contractor Tom Silva breaks down the process of repairing a broken board step by step.
Pulling the Nails
The square-edged deck boards in this picture were face-nailed to the joists. Silva starts to remove the board by looking for a telltale row of nailheads. Then, he uses a cat’s paw to pry out each nail in the board. If a nail is missing a head, using nail-pulling pliers with a rolling motion can help.
If you’re dealing with a particularly stubborn nail, and if saving the wood’s surface isn’t a priority, try a more aggressive technique. Place the cat’s paw claws next to the nail at 45 degrees. Hammer the head into the wood until the claws straddle the nail shaft. If they don’t grab, place the cylindrical knuckle over the nailhead, whack the tool with a hammer to make a dip in the surrounding surface, and try again. Then, gently rock the handle. That leaves the nail no choice but to back out.
Removing the Broken Board
After removing all the nails, it’s time to take out the damaged board. Before you start, score the paint along the joints where it meets neighboring boards. That breaks the bond to make removal that much easier.
Silva now jams a pry bar under the break, using it like a lever to lift up one end of the board, and pulls it out. He repeats the process for the other end.
If you’re dealing with a particularly long board, you may need to work your way along the length and gradually loosen it from the joists beneath.
Pro Tip: Tom Silva, This Old House general contractor, notes that these square-edged deck boards are typically face-nailed to the joists. To find every fastener, he looks for a telltale row of nailheads running across the board at each joist location, then uses a cat’s paw to pry out each nail. If a nail is missing a head, he switches to nail-pulling pliers to grip the shaft.
Making the Cleats
Cleats are essential supports that stabilize the new board and stop it from shifting over time. To make them, Silva uses the damaged board as a sizing guide for cutting.
Cut two pieces, each about three times longer than the board’s width. Squeeze a bead of construction adhesive on the ends of each cleat’s unpainted face, as shown in the picture.
Installing the Cleats
Next, Silva snugs the first cleat, adhesive side up, under the neighboring boards. He drills pilot holes through the deck and into the cleat, then fastens the cleat to the boards with stainless steel trim-head screws. The other cleat goes on the same way, just at the opposite end.
Cutting and Fastening the New Board
Silva uses clear Douglas fir for new porch boards, since it’s more stable and holds paint better than a cheaper type of wood. He measures and marks out the length of the original board, then cuts a single board to length. The cut board uses adhesive at each joist and cleat, secured with two hot-dip galvanized 8d nails that resist corrosion.
To support the ends of the new board where it doesn’t land on a joist, cut a pair of cleats from the cracked board you removed, making each cleat three times longer than its width. Squeeze construction adhesive on the ends of each cleat and fasten them to the neighboring boards so they sit flush with the joist tops, giving the replacement board a solid landing at both ends.
Apply a bead of adhesive to each joist and cleat, then secure it at those locations such that the board is flush with its surroundings. Place the nails 1/2 inch from the edges, and tap them in gradually to prevent splitting the wood.
Setting the Nailheads for Painting
Setting the nailheads helps make a smooth surface that’s ready for painting. Silva uses a nailset to drive each nailhead slightly below the board’s surface, a technique called countersinking.
Pro Tip: Tom Silva drives nails at an angle to really lock down the board, then finishes with a nailset, driving the nail heads 1/16 inch below the surface of the wood. As he puts it: “Driving nails at an angle really locks down the tread.” Once set, he hides the holes with a dab of wood-colored putty.
Painting the New Board
Once you apply a coat of oil-based primer and two coats of deck paint, the nailheads you countersunk can look invisible. If you have extra paint the same color as the other boards, take it out for the finishing touches. Otherwise, bring a picture or old sample to your paint store for a freshly-mixed custom color.
Sand the entire repaired area smooth, and feather the edges to blend with the surrounding boards. Apply the primer to the new board and any exposed wood. Once that’s dry, apply the first coat of deck paint. Let it dry completely before you apply the second coating.
After priming, fill all countersunk nail holes with exterior-grade wood filler and let it dry completely before moving on to the first coat of paint. This extra step ensures a perfectly smooth, seamless finish once the deck paint goes on.
