Does subfloor go under interior walls?

Author: Miss Hailie Veum  |  Last update: Wednesday, January 28, 2026

Do walls sit on top of subfloor? Walls are built on top of a home's subfloor, so replacing the subfloor can sometimes require removing the walls.

Should there be a gap between subfloor and wall?

It's standard to have between 1/4'' and 1/2'' of a gap between the floor and the sheetrock. This is to help prevent any moisture on the floor from destroying the sheetrock. Even that bigger gap on the right should be fine if it is not above the bottom plate of wood.

Does framing go on top of subfloor?

If your basement renovation is to include a plywood subfloor, or the 2'x2' subfloor panels, be sure to install the subfloor first, then frame the wall overtop. Having the 2×4 wall sit on the subfloor will protect the lumber from moisture issues or any minor flooding.

What does the subfloor sit on?

The subfloor sits on top of the joists. This allows your floors to have a continuous structural surface over the floor joists. There are different materials that can be used for the subflooring. Those are wood planks, plywood, OSB (Oriented Strand Board) and concrete.

Do walls go up before flooring?

Major Structural Work: If you're knocking down walls or adding extensions, it's best to complete this heavy-duty work before flooring. The vibrations and debris from structural changes can damage flooring.

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Should the subfloor go under the walls?

Do walls sit on top of subfloor? Walls are built on top of a home's subfloor, so replacing the subfloor can sometimes require removing the walls.

Do you put flooring down before drywall?

While the flooring that is laid down after the drywall is installed will correct imperfections in the floor, any small hill in the concrete will cause a full sheet of drywall to be out of level if the drywall is placed directly on the floor.

What is underneath the subfloor?

The floors in your home are made up of several layers, beginning with the joists below, the subfloor and underlayment in the middle, and the actual flooring material at the top. Joists. Joists are the first, lowest layer of flooring and support everything above.

Should subfloor be nailed or screwed down?

Rather than nails, screws are best to use for subfloors — these fasteners are convenient, easy to remove and capable of providing torque that nails lack. Because of their structure, screws can penetrate plywood more easily and improve the connection, whereas nails can weaken the plywood.

What is the correct order of installation for a floor frame?

  1. Step 1: Square the Sill Plate Layout on the Foundation. ...
  2. Step 2: Cut, Drill and Attach the Sill Plates. ...
  3. Step 3: Build Basement Bearing Walls - Where Necessary. ...
  4. Step 4: Layout the Joist Spacing on the Sill Plates. ...
  5. Step 5: Attach the Rim Joists. ...
  6. Step 6: Cut and Install the Floor Joists Between the Rim Joists.

Do cabinets go on top of subfloor?

Yes and no. It really depends on your preference, the type of cabinet, and more importantly, on the type of kitchen flooring you have and how it is installed. It isn't necessary to have your kitchen cabinets sit on the subfloor, and it certainly isn't the desired option among contractors.

How to attach a wall to a subfloor?

For wood subfloors with joists, nail the wall frame through the bottom plate to the floor with two nails at every available joist. Joists are not visible. They are located under the subfloor. Nail between the joists, too, wherever possible.

Do you build walls on top of subfloor?

A Basement partition walls support no load, so it's fine to build them on top of your subfloor panels. This is actually a better and easier approach.

Should drywall touch the subfloor?

Always leave a 1/2-inch gap at the floor. This allows for floor and wall expansion without cracking the drywall. It also helps prevents moisture wicking if the floor floods. Wear work gloves, safety goggles and a dust mask when hanging drywall.

How much space should I leave between flooring and wall?

Generally, a gap of 1/4 inch to 1/2 inch is recommended for hardwood flooring, while laminate flooring typically requires a gap of 1/4 inch to 3/8 inch. It's important to note that the expansion gap should be consistent throughout the room, including around obstacles such as doorways, cabinets, and pipes.

Does subfloor need to be perfectly level?

No subfloor is perfectly level, but any signs of unevenness and high or low spots must be remedied. Please follow these requirements: Subfloor unevenness cannot be greater than 3/16 of an inch over a 10-foot span or 1/8 inch over a 6-foot span.

How often do you screw down a subfloor?

Subfloor. Screw spacing should be 6" o.c. at the boundaries and 12" o.c. in the field, assuming an unblocked diaphragm. For blocked diaphragms increase the numbers of screws by 15%.

Should I nail or staple my subfloor?

1. Engineered wood flooring or thinner solid wood flooring is better suited to stapling than thicker, harder wood options. 2. Thick engineered and solid wood flooring and species of flooring that are particularly hard are undoubtedly best nailed down.

Do I need a vapor barrier under subfloor?

When moisture penetrates your flooring, it can cause mold, mildew, and the potential for water damage. A moisture barrier helps control the water vapor's movement to help protect your floors. Therefore, if you're installing floors in an area that sees moisture, even a little, a vapor barrier is needed.

What should a subfloor look like?

The subfloor is typically made of plywood or OSB, ranging from 19/32 inches to 1-1/8 inches thick. Subfloor plywood or OSB sheets typically have tongue-and-groove edges to reduce floor sagging and bounce. If the bottom-most floor is a concrete slab, its definition as a subfloor becomes more fluid.

Is OSB better than plywood for subfloor?

Both plywood and OSB are effective choices for your subfloor needs, but OSB may be a better option for a garage than plywood. Plywood is a better option for projects that require a lot of cutting and molding, while OSB is a good option for those who need to cover areas where moisture exposure may be an issue.

Why drywall ceiling first?

Hang the Ceiling First

This makes it much easier to manage and attach the panels since you will not have to fumble around with the screws, measuring tape, and so on. Screws for drywall lids should be placed no closer than 16” from the wall. This allows the drywall to have a bit of flexibility to prevent ceiling cracks.

What goes first flooring or walls?

Once you have prepped your walls, you are ready to install the flooring in your home. You should do this before painting any of the walls. That way if you do cause any damage while installing the floors you don't have to repaint areas. This is especially important if you're installing hardwood floors in your home.

Should you leave a gap between sheets of drywall?

Joints are too tight

Without enough space when this happens, you'll get cracks. Keep a 1/8-inch space between sheets during installation to keep this from happening. Using a guide can help make sure your sheets are properly spaced throughout the job.

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