Top Tips to Replace a Subfloor under a Wall

Replacing a subfloor below a wall is necessary once the subfloor is no longer structurally sound. The subfloor is the solid foundation underneath the floor covering which you rely on for the stability of the ground and of walls. It’s not the major support system–that is the work of beams, posts, and joists–but it does its share of the job.

The subfloor may be rotted out by water often true with walls behind shower walls or controls under badly functioning windows. Sometimes, you can remove pieces of the subfloor without needing to take the wall down.

Tips to Replace a Subfloor under a Wall
Tips to Replace a Subfloor under a Wall

Wall and Floor System Basics

Walls and floors are interconnected, creating a structurally tight system. From bottom to top, the system will look somewhat like this:

Joist: A joist is a long, horizontal piece of timber, normally a two-by-eight or two-by-ten, that holds up the floor.

Subfloor: The subfloor is nailed to the top of the joist. Often 19/32- to 1 1/8-inch thick plywood or OSB, the subfloor may run continuously through the joist or 2 segments of subfloor may meet on a joist.

Underlayment: Some floors have a thin underlayment that helps to smooth the subfloor for the floor covering. Not all flooring will have this.

Floor Covering: The floor covering may be laminate floors, vinyl tile, luxury vinyl plank, or some other type of flooring.

Bottom Wall Plate: The bottom wall socket is your bottom-most area of the wall. It’s normally an 8-foot-long two-by-four. Wall studs are nailed vertically to the bottom wall plate. The wall plate itself is nailed (downward) to the subfloor, with claws even extending to the joist.

All items except for the underlayment and flooring covering remainder under and are nailed to the bottom wall plate.

Eliminating the Subfloor Under Walls

Eliminating subflooring while the wall is set up is difficult because the subfloor is trapped beneath the wall. The process is very similar to slipping out a book nailed into the floor as a man is standing on it. It can be done, but with some hard work and patience.

You can only remove part of the subfloor. To eliminate subfloor throughout an entire wall, you’ll have to take out the wall.

A secure width to eliminate is 14 inches because this represents the length between two joints or two claws.

When you experience a rotten subfloor, you often realize that the rot extends into the wall or other areas of the floor. So, be ready to replace more than just the subfloor.

Read also: DIY Home Gym Floor – The Home Depot Flooring A-Z

What You Will Need

Gear / Tools

Flat prybar

Circular saw

Utility knife

Oscillating multi-tool and alloy blade

Hand saw

Drill

Instructions

Turn Off Electricity and Water

At the electrical service panel, switch off any circuits which operate to the area where you’ll be eliminating the subfloor. Close off any affected water lines, also. In case you’ve got intermediary water shut-offs, shut off the water here. Otherwise, shut off water to the whole house at the key shut-off valve.

Eliminate the Baseboard

With the horizontal prybar, gently remove the baseboard and any quarter-round trim. Place these pieces aside.

Remove Sections of Drywall

Drywall may extend across the ground covering. In that case, cut away a section into the necessary width and about 1-foot high.

Eliminate the Floor Covering

Eliminate the floor covering directly over the subfloor you need to remove. Also get rid of a couple more inches outside to give yourself room to work. Some floor coverings will lift off, while some will require cutting.

Laminate flooring and luxury vinyl plank flooring installed parallel to the wall should easily lift off. Self-adhesive vinyl tiles will peel off. Sheet vinyl can be dragged back.

Ceramic and ceramic tile will have to be broken, in addition to the thin-set mortar ought to be chipped away. Solid hardwood and engineered wood flooring installed parallel to the wall can be pried off, though some boards will get damaged.

Eliminate Any Underlayment

Some floors have a thin underlayment between the subfloor and the floor covering. For laminate flooring felt or foam underlayment, cut away a section with the utility knife. For 1/4-inch luan underlayment board, place the circular saw at the appropriate thickness to cut only into the luan but not to any materials under it.

Cut Away the Nails

Attach the metal-cutting blade into the oscillating multi-tool. While wearing eye and hearing protection, turn on the instrument and insert the blade below the wall. Cutaway all claws which run downhill from the bottom wall plate.

Cut Away the Subfloor

Place the circular saw to the proper depth to cut just the subfloor but none of the substances beneath the subfloor. The circular saw can’t cut flush with the wall, so cut as close as you can get to it. Most circular saws will permit you to cut as close as an inch or 2. Continue two cuts with the hand found along the face of the cut-out square until you reach the wall’s bottom plate.

Eliminate the Subfloor From Beneath the Wall

If the subfloor is heavily rotted out, you could have the ability to pull back to the rest of the section of the subfloor and eliminate it. Otherwise, attach a 3/4-inch auger bit to the drill and drill to a depth of 3 1/2 inches beneath the wall bottom plate on either side of the rotted area. The auger bit effectively functions as a saw to cut the wood away. If the border of the subfloor rests on the joist, the part of the subfloor should pull out. Otherwise, proceed to the next step.

Eliminate Subfloor From Other Side (Optional)

If the subfloor is a continuous sheet that extends beyond the wall, then you won’t be able to pull out the section which you’re working on. Repeat all the previous steps on the opposite side of the wall to free up the subfloor so you can eliminate it.

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