How to Install Underlay
If you have an old wood floor and you want to cover it with a new wood floor --- or with vinyl, tile, carpet or almost any other kind of flooring --- you should install an underlay first. A plywood underlay gives you a nice flat surface to start with, covering up surface variations in the base floor that could cause problems in the new flooring. As with all wood products, plywood expands and contracts with the local environment. To minimize this movement, let the plywood acclimate to the room for a week or more before installation. Does this Spark an idea?
Things You'll Need
- 5/8-inch plywood
- Pencil
- Screw gun
- 1-1/2-inch drywall screws
- Circular saw
- Floor leveling compound
- Drywall knife
- Mixing bit for the drill
- Bucket
Instructions
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Lay a sheet of plywood in one corner of the room, bordered by two walls. Set it back from both walls by approximately 3/8 inch. This "expansion gap" will allow for the natural movement of the wood, and must be maintained all along the walls.
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2
Sink screws every 6 inches or so along the edges and throughout the whole surface of the board. Make sure the heads of the screws are completely sunk into the wood and not sticking up anywhere.
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Set the next plywood sheet off the end of the previous one. Screw it down. Repeat, laying the sheets end to end to make a whole course. Keep your expansion gap at the wall, while butting the ends of the boards tightly to one another. Cut the last board to fit with your circular saw.
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4
Start the second row of boards from the opposite end of the floor that you did the first row so the ends of the boards are staggered between rows. Repeat and continue, covering the whole floor.
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5
Mix a batch of liquid leveling compound with a drill and mixing bit in a bucket, according to the instructions on the packaging. The leveler should be very thin and watery. Pour it over all holes, gaps and spaces on the plywood --- except the expansion gaps around the perimeter, which must be left open. Let it set for 12 hours. The underlay is now ready for top-flooring.
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