DIY Network

How to Replace a Subfloor

A subfloor in a shower can grow mold on it after some time. Replace an old, rotted subfloor with a new one.

More in Floors

replace an old, rotted subfloor with a new one

Step 1: Remove the Nails

Find and remove the existing nails.

Step 2: Cut Around the Floor Base

Cut around the base of the floor with a reciprocating saw.

cut around base of floor with reciprocating saw

Step 3: Turn Off the Power

Be sure to turn off the power to the room since there could be wires running under the floor or behind the wall. If you are unsure about the placement of the wires, have a spotter below to watch the blade as it moves through the wood.

Step 4: Cut all of the Plywood

Keep the blade at a 45-degree angle to the floor to make sure that you cut all of the plywood out from underneath the bottom

cut all of the old plywood out

Step 5: Snap a Line

Snap a line along the center of the joist to keep it available as a nailer for the new subfloor.

snap line along center of joist

Step 6: Cut Along the Line

Use a circular saw to cut along the line while riping out the rest of the nails.

cut along line with circular saw

Step 7: Measure and Cut the new Plywood

With everything cleaned out, take measurements for the new subfloor. Transfer the measurements to the new 1/2" plywood, and make the cuts with a circular saw. Use a jigsaw if necessary to cut any indentations for the vent stack.

take measurements for new subfloor

Step 8: Place the Boards

With the old floor gone, place a piece of scrap lumber across the joists to give yourself a nice safe place to stand on. The new plywood will be attached with construction adhesive and screws. Set the boards in place.