Replacing a Subfloor

A circular saw cuts straight lines on replacement subflooring.

Subflooring provides support for the flooring of your home. Subflooring weakened by age, water or dry rot loses its structural integrity. This causes areas of your floor to sink and feel spongy. In time, the spongy areas will give way, creating a safety hazard for persons walking on the floor and allowing moisture and bugs access to your home. Replacing weakened subflooring will keep your home safe, bug-free and avoid costly repairs in the future.

Things You'll Need

• Claw hammer
• Carpenter's pencil
• Reciprocating saw
• Screw gun with #2 Phillips head tip adapter
• Pry bar
• Tape measure
• Plywood
• Circular saw
• 2-inch wood screws

Instructions

1. Remove the flooring from the area with the weakened subfloor.

2. Tap the weakened subfloor with a claw hammer to determine the size of the weakened area. Mark the floor joist past the weakened area with a carpenter's pencil.

3. Outline the area of subfloor to replace. Two sides of the outlined area need to fall on the center of the floor joists to support the replaced subfloor.

4. Remove the weakened section of subfloor. Cut along the outlined area with a reciprocating saw. Make sure not to cut too deeply into the floor joists supporting the floor.

5. Remove the fasteners from the area inside of the cut outline. Pull nails with a claw hammer or remove wood screws with a screw gun equipped with a #2 Phillips head tip adapter.

6. Slide the hooked end of a pry bar into one cut side of the weakened subfloor. Push the pry bar away from the cut away to free the old subfloor from the floor joists.

7. Measure the length and width of the removed area with a tape measure.

8. Mark a piece of plywood to fit inside the open area of subflooring with a carpenter's pencil.

9. Cut the plywood to the desired length and width with a circular saw.

10. Place the cut piece of plywood into the opening in the subfloor.

11. Secure the plywood to the floor joists. Place one 2-inch wood screw every 16 inches. The wood screws need to run through the plywood and into the floor joists. Placing screws further apart than 16 inches will cause the newly installed section of subfloor to buckle when exposed to moisture.

12. Install new flooring when all sections of the weakened subfloor are removed.

Tips & Warnings

• Cover or block the opening cut in the subfloor while you cut the plywood to size.

References

• The Tile Doctor: Repair Subfloor Water Damage
• Old House Web: Wood Floor Repairs
• My Great Home: Repairing Your Vinyl Floor