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.

Replace a Subfloor under a Wall
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 the 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



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.

How to replace subfloor

Replacing a subfloor is a fairly easy task, but it is important to take your time and follow the correct steps to ensure a successful installation. Here are some tips to help you get the job done:

1. Plan ahead. Make sure you know exactly what needs to be done before you start, so you don’t run into any surprises along the way.

2. Remove the old subfloor. This can be a bit of a tricky process, but it’s important to get rid of all the old material so the new subfloor can be installed properly.

3. Install the new subfloor. Make sure it’s level and fits securely in place.

4. Seal the seams between the subfloor and the wall. This will help prevent moisture from seeping through the cracks and causing damage to the new subfloor.

5. Test the flooring before you install it. Make sure it fits properly and is in good condition before you start putting it down.

Replacing a subfloor can be a tricky process, but if you follow these tips, you’ll be able to get the job done quickly and efficiently.

Replace bathroom subfloor

Replacing a subfloor can be a daunting task, but with some careful planning, it can be a relatively easy project. Here are a few tips to help make the process go smoothly:

1. Plan Ahead

Before starting any project, it is important to plan ahead and make sure you have all of the necessary supplies and tools. This is especially true when replacing a subfloor, as there are a number of specific tools and materials required for the job.

2. Use the Right Tools

When replacing a subfloor, it is important to use the right tools for the job. In particular, you will need a saw to cut the new subfloor to size, a drill to create pilot holes, and a hammer to drive nails.

3. Measure Twice, Cut Once

It is important to measure the area you are replacing twice before cutting the new subfloor to size. This will help ensure that the new subfloor fits correctly and does not need to be cut again later.

4. Use a Level

When installing the new subfloor, it is important to use a level to ensure that it is installed correctly. This will help prevent any future problems with the flooring.

5. Use a Square

In addition to using a level, it is also important to use a square when installing the new subfloor. This will help ensure that all of the edges are aligned correctly and that the subfloor is installed evenly.

6. Use Nails or Screws

When installing the new subfloor, it is important to use nails or screws to secure it in place. This will help keep the subfloor from moving and ensure that it stays in place.

7. Seal the Edges

Once the new subfloor is installed, it is important to seal the edges to prevent moisture from seeping underneath. This will help protect the subfloor and prolong its life.

8. Test Before Finishing

Before finishing the project, it is important to test the new subfloor to make sure it is installed correctly and does not need any additional adjustments. This will help ensure that the job is done correctly and that there are no problems with the flooring later on.

How to replace subfloor under wall

Replacing the subfloor under a wall is a fairly straightforward process. First, you’ll need to remove the baseboard and door casing around the wall. You can then use a saw to cut through the drywall and insulation around the perimeter of the wall.

Once you have removed the drywall and insulation, you can start removing the old subfloor. You can use a pry bar to remove any nails or staples that are holding the subfloor in place. Once the old subfloor is removed, you can install new subflooring using nails or staples. Finally, you can reinstall the drywall and insulation around the perimeter of the wall and replace the baseboard and door casing.

Replace a Subfloor under a Wall

In order to replace a subfloor under a wall, you will need at least one helper. Be sure that all the electrical wires and plumbing fixtures are turned off before starting any work. Put on safety glasses or goggles for protection from flying debris.

Measure your opening with a tape measure and mark each end of the floor joists as well as their centers so it is easy to identify where they line up when removing them. You can rent an electric jackhammer drill machine if you do not have access to power tools like this in your home, but be careful because these machines can cause injury if used incorrectly by someone without experience using them.

Make sure that anyone who uses the jackhammer wears earplugs or muffs for hearing protection since these drills make a lot of noise. Loosen the nails in the floor joists with a pry bar or hammer and then remove them. If any of the floor joists are damaged, replace them with new ones before continuing.

Place the new subfloor in position and fasten it to the floor joists using construction adhesive and nails or screws. Be sure to caulk around the edges of the new subfloor to create a watertight seal. Finally, reattach the electrical wires and plumbing fixtures and you’re done!

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