How to Replace Subfloor Under Wall?

Do you have a subfloor that is no longer sound structurally? One of the wise decisions to take in this situation is to replace the subfloor under the wall.

A subfloor typically refers to a strong base that stays underneath the floor covering. It is made to ensure that the floor and walls in the room are stable.

It should be made clear that the function of a subfloor is different from that of the joists, posts, and beam. Unlike these main support systems, a subfloor only contributes fairly to the flooring work.

Sometimes, replacing a subfloor can become a bigger task, leading to taking down the wall. However, you can get the job done in some cases under the wall. To do this, after seeing the signs that you need to replace your subfloor, get the right tools and follow the appropriate steps.

How to Replace Subfloor Under Wall

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Signs you Need to Replace a Subfloor

A very good question you must ask yourself is,”what should make me think it’s time to replace my subfloor?” Below are some of the common signs you need to watch out for:

  • Squeaking floor: A problem with your subfloor could result in the loud squeaking of the floor. This usually occurs when the subfloor rubs against the nail, which is supposed to hold the subfloor and the joists firmly. The disturbing noise could be generated the moment the nails work themselves loose from the joists.
  • Sinking floor: Do you notice that your floor is gradually sinking between the floor joists? This is an indication that something is wrong with your subfloor. The sinking of the floor can be because of moisture issues or improper subfloor installation.
  • Cupping floorboards: Seeing your floorboards curling along the length of the board is a sign that you need a subfloor replacement. This issue is usually due to exposure to moisture.
  • Water issue: Your subfloor may be damaged if water (from a leaking roof, sink, or drain) sits between it and the finished flooring. The sign of water damage is the smell of mold or mildew in the room. In this situation, find the affected area to know where to replace it.
  • Bouncing floor: It could be a surefire sign that you need a replacement if your floor appears a little springy, bouncy, or spongy.

Steps of Replacing Subfloor Under Wall

After seeing the common signs that could indicate that you need to replace your subfloor, below are steps you can take to execute the replacement process:

Step1: Get the needed tools/equipment & materials and turn off the circuit & affected water line

The first important step to take is to get tools (flat pry bar, circular saw, utility knife, oscillating multi-tool, and metal blade, hand saw, and drill) and materials (heavy-duty trash bags, eye protection, and ear protection).

Ensure any circuits that run to the area where to remove the subfloor are turned off at the electric service panel. Also, shut off the affected lines.

Step 2: Remove the baseboard

Know where the problem is and remove the baseboard and any close quarter-round trim gently with the flat pry bar. Then set the pieces aside.

Step 3: Remove drywall sections

Cut away sections of drywall. Also, remove a section that extends over the floor covering. You can cut to the required width up to 1-foot high. Put the trashin the heavy-duty trash bag.

Step 4: Cut away the floor covering

Cut away the floor covering above the affected subfloor. And to get more room to work, you can remove more inches beyond. Note that while some floor coverings will require cutting, others will lift off easily.

Step 5: Cut away any underlayment

Use the Utility knife to cut away a section of 4he underlayment. If your luan underlayment board is 1/4-inch, set the circular saw at the proper depth and cut only luan (avoid cutting any material beneath it).

Step 6: Remove the nails

To remove all nails, attach a metal-cutting blade to oscillating multi-tool, turn it on, and insert the blade under the bottom wall plate. But ensure you wear eye and hearing protection. Instead of cutting, you can use a nail puller tool to pull the nail out.

Step 7: Cut away the subfloor

To cut only the subfloor, set the circular saw to the right depth. Use the saw along the side of the cut-out square until you get to the wall’s bottom plate.

Step 8: Remove the subfloor from under the wall

For heavily-rooted subfloor, you can pull back on the remaining section of the subfloor and get it out by hand. Otherwise, drill to a depth of 3 1/2 inches underneath the wall bottom plate (on both sides of the rotted area) using a drill with an attached 3/4-inch auger bit. The auger bit helps cut away at the wood. Besides, the section of the subfloor should pull out if the edge of the subfloor sits on the joists. If not, move to step 9.

Step 9: Get the Subfloor out from the other side

In a situation where your subfloor is a continuous sheet that goes beyond the wall, it may be difficult to pull the affected section out. To free up the subfloor to remove it, repeat all the steps on the other side of the wall.

Frequently Asked Questions (FAQS)

Check out below some of the frequently asked questions and the short answers to them:

Why do you need a subfloor?

A subfloor is needed because through it, the finished flooring can be strong enough to handle people’s weights or anything put on it, such as refrigerators, stoves, etc.

Why Would You Need to Replace a Subfloor?

Do you have a subfloor that is no longer structurally sound and walls and floors with compromised stability? Then you would need a Subfloor replacement.


Subfloors are technically installed to last for a very time (about two to three decades). Replacing a damaged subfloor is easy, but if you lack the confidence to do it yourself, you can hire a professional. Moreso, it’s important that you find a solution to what led to the damage of the subfloor to prevent the problem from reoccurring. Generally, you may need replacement if the damage to your subfloor is caused by overexposure to moisture.

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