A piano bench not only provides a comfortable seating area for the player, it can become a valuable storage tool as well. Over time, too much sheet music stuffed in the bench with the weight of the player on top of it can cause the bottom of the bench to fall out. This is a common problem that can happen with any type of bench. It's easy to fix and secure so it won't happen again. It's even a good idea for new benches to prevent a failure later.
Step 1- Get Your Measurements
The first thing you want to do is measure the current bench. A standard piano bench is typically 14 inches wide, by 29 long. However, some benches have been custom tailored to work with specific models of pianos, so you still need to measure. Measure the underbelly of the bench, including the length and width. With this in hand you can purchase a piece of plywood to the exact measurements. You may also want to get the materials to make a cross brace for the bottom of the bench as well. For this you will want 2 pieces of 2X4 lumber that will span diagonally across the bottom of each side of the bench.
Step 2- Attach the Plywood
Use a good quality wood glue to secure the plywood piece to the bottom of the bench. Use clamps to secure this for several hours. Most people suggest giving the wood glue at least 12 hours to form a strong bond. After the glue has cured, you can use wood screws to secure the corners, and use 2 wood screws for each side along the glue lines. This gives the bench more security.
Step 3- Create a Crossbrace
If you know that you will be putting lots of music, books, and other items in the bench, you may want to consider adding a cross brace. A cross brace won't work on benches that are decorative as it will make them look strange. You can skirt around the bottom of the bench to hide this if you think it's necessary. This may sound extreme, but it will protect you from fallouts later. Clamp the 2X4s in a criss-cross pattern under the bench. Flip the bench back over on its legs to make sure you won't see the cross brace. If you don't have a way to place a cross brace without it showing, you may want to skip this step. Flip the bench back over and use wood screws and a drill to secure the cross brace. Some people choose to use a single piece of lumber for this, and it will still add extra security.
Step 4- Sand the Edges
You can now use the sander to gently sand around the edges making sure no rough sides remain. This is mainly cosmetic, but can also protect the player's legs from rubbing against a piece of wood that is raw and unfinished.