How To Replace Subfloor Under Wall?

    replacing subfloor under wall

    The replacement of a subfloor beneath a wall becomes necessary when the subfloor no longer serves its structural purpose. The subfloor is the strong foundation beneath the floor covering on which you may rely in order to ensure that both the ground and the walls are stable.

    Although it is not the primary structural support system (that role is performed by beams, posts, and joists), it contributes to the overall structure. The subfloor may get rotted out by the water, which is common with walls behind shower walls or controls behind windows that are broken.

    Even though replacing a subfloor can occasionally turn into a larger undertaking, there are some situations in which you can replace parts of the subfloor without having to pull down the whole wall.

    However, before knowing "how to replace subfloor under wall," you need to understand the signs that indicate if you need to replace your subfloor or not.

    How To Know That It's Time To Replace The Subfloor

    A subfloor can endure as long as the building itself is under standard conditions. However, if a subfloor is broken or substandard, it may only last up to 20 years. If this is the case, begin by peeling back the layers of flooring. Here are 5 signs that will show you that you need a subfloor replacement. 


    It's not unusual for the flooring to have a slight squeak. However, if your floor is beginning to sound like the Tin Man without his grease can, it may be time to take action.

    2-Sinking Sections

    When strolling through a sitting room feels like a walk-through on sloping hills, problems with the subfloor become much more obvious. If a floor starts to sink between floor joists, you know there's a problem, and replacing subfloor is necessary.

    3-Cupping Floorboards

    When your flooring begins to curl along the length of the board, this is known as cupping. Moisture is the most common reason for cupping floorboards.

    4-Cracked And Popping Tiles

    Something isn't right if your tiles are cracking and popping. You'll know it's a subfloor problem if the back of the dislodged tile has dried thin-set completely.

    5-Water Damage

    Water is definitely a floor's worst enemy. There's a fair probability there's been some damage if there's been water lingering between the finished flooring and the subfloor.

    How To Replace Subfloor Under Wall?

    Now that you know about different signs that indicate that you need a subfloor replacement, it is time to discover how you can replace it. However, if you think you are unable to undertake this task, it is better to leave it to the experts.

    1- Identifying the Extend of Floor Damage

    To begin replacing subfloor, determine the degree of the damage. Remove the floor covering on both sides of the wall to look for the damaged subfloor. The next question to consider is why the subfloor began to decay in the first place.

    Have you addressed the source of the problem in order for your new subfloor to remain dry? Before starting subfloor replacement, repair any leaking windows, doors, roof shingles, or water pipes, as well as any crawl space dampness.

    2- Demolishing the Drywall

    The next step while replacing subfloor is to figure out if you're dealing with a load-bearing wall. If you are, come to a halt and learn how to adequately shore up the wall from all sides or below. When sawing, make sure to wear the appropriate personal protection equipment, such as safety glasses and a dust mask.

    The drywall above the damaged floors must now be removed. Use a proper circular saw cut to ensure that you are only cutting through drywall and not studs or pipes. As you cut off an area-wide enough for you to properly reach the damage, exercise extreme caution.

    Repeat on the other side of the wall, and cut out any insulation which is in the way with a reciprocating saw. You should be able to identify if the wall studs or floor plates are compromised at this point.

    Even if the floor plates (horizontal boards connecting the wall studs) appear to be in good condition, they must be removed in order to remove the floorboards beneath the wall. Unscrew them and drive them out further with a rubber mallet. At this stage, you should also cut off the edges of any damaged wall studs.

    3- Removing Floorboards Under Walls

    There will be nothing standing in the way of the subfloor being entirely removed now. You must now set the saw height to the width of the subfloor, just as you did previously to avoid cutting any wiring or pipelines by setting the circular saw to the appropriate width of the drywall.

    If the floor is in such bad shape that you can push a chunk out and check the thickness, go through with it. Otherwise, on the affected edge furthest from any walls, cut a tiny test section with a minimum height of about 3/8 inch.

    Adjust your saw's height to 1/2-inch increments until you've determined the true width of your subfloor. Then, in a rectangle shape, cut out the compromised subfloor, leaving the other edges unharmed. To make re-installation smoother, expand your incisions to reveal half of a floor joist.

    Inspect the floor joists for deterioration once they've been uncovered. To strengthen the floor joists, cut out any defective areas and put new wood on both sides.

    4-Putting Things Back Together

    Now that you've removed the subfloor, all you have to do now is to complete the subfloor replacement. If required, repair the floor joists before installing a new subfloor panel. Replace any broken wall studs and fix the floor plate. Finally, replace the floor covering and reattach the insulation as well as drywall.


    As you have now discovered “how to replace subfloor under wall,” you can now replace a subfloor by following these steps. However, always make sure to address the issue that caused the subfloor to be damaged, or whatever the reason was for having to replace it since if you don't, the problem will resurface. And, if you are unsure about replacing subfloor beneath a wall, you should hire a professional.

    Turn to CityLocal Pro to find flooring experts in your area. CityLocal Pro is your go-to platform where you can locate and hire services from certified and professional companies. You can also look for customer reviews for these service providers, assisting you to make an informed decision.

    Image Credit: Youtube - Jeffrey Major Subfloor Replacement Excerpt

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