How to install plywood subfloor over joists? (2024)

How to install plywood subfloor over joists?

Ply should always be laid with the grain running across the joists, not along the joist, to maximise the strength. Laying them length ways down a joist will cause them to crack along the grain which could end up in serious injury and or damage. The smaller the gap between joists the stronger the board will be.

How do you lay plywood over joists?

Ply should always be laid with the grain running across the joists, not along the joist, to maximise the strength. Laying them length ways down a joist will cause them to crack along the grain which could end up in serious injury and or damage. The smaller the gap between joists the stronger the board will be.

Can I screw subfloor to joists?

You can put an end to the squeaking by screwing the subfloor to the floor joists after you remove the old carpet and pad, but before the new carpet is installed. You'll need to do a little work before the carpet layers show up, but you'll have a quiet floor when all's said and done.

Should plywood underlayment be screwed to joists?

The underlayment is usually stapled to the sub floor with a pneumatic stapler, but can be fastened through the subfloor into the joists with nails or screws instead.

Should I glue plywood to joists?

How to Adhere Your Subfloor Panels to Joists. To glue or not to glue? The answer: Glue. Although using a subfloor adhesive (or subfloor glue) is not required by code, it is a standard practice that can help prevent floor squeaks by reducing the chance for movement at the panel-to-joist connection.

Should plywood subfloor be nailed or screwed?

Screws are preferred over nails for subfloor and underlayment installations as they provide strong and tight connections that help prevent the floor from squeaking. Before starting your next subfloor or underlayment installation, make sure you have the right subfloor screw gun for the job.

Is it better to nail or screw floor joists?

Screws are often chosen for subfloor installations because their joining strength helps to prevent squeaky floors. Nails are more flexible and will give a little more with hardwood flooring, so they're often the choice for panel installation.

How far apart should screws be for plywood subfloor?

Generally, nails (6d ring or screw shank, or 8d common) should be spaced 6 inches on center along supported panel edges and 12 inches on center on the panels' interior supports, or as specified on the construction drawings.

What is the best adhesive for subfloor to joist?

Titebond Solvent-Based Subfloor Construction Adhesive is a professional strength formula that is specifically designed for subfloor installations and general plywood use. It provides a permanent bond that remains flexible, reduces nailing and prevents squeaky floors.

What do you put under plywood subfloor?

Underlayment is a thinner material that lies over the subfloor. While underlayment may add a modest amount of stiffness to a floor assembly, it does not strengthen a floor or enhance it structurally. Plywood is only one type of underlayment.

Do you need vapor barrier on plywood subfloor?

Your plywood would most likely be on a sleeper system (floating wood planks on concrete). Having a vapor barrier below the sleepers is ideal as moisture will not get to the plywood. Regarding on-grade applications, if their is a basem*nt underneath, then you will not need a vapor barrier on top of the plywood.

Does subfloor plywood need to be tongue-and-groove?

You can use standard plywood for subfloors, but it is more common to use tongue-and-groove sheets that interlock along the edges. The spacing of the joists governs the recommended thickness of the plywood subfloor.

Do you glue tongue-and-groove plywood for subfloor?

Gluing is recommended and can add strength to the floor. Glue subfloor panels to prevent squeaks and uneven flooring. Only glue two or three panels at a time so that they can be fastened before adhesive hardens. Placing a small bead of glue in the T&G groove can add strength and stiffness to your floor.

What is the best glue for plywood to I joists?

Hexion's phenol resorcinol-based adhesives are the standard for strength and long-term durability in the I-joist market. These adhesives bond the wood together that form the I-joist.

Can you sister floor joists with plywood?

Sistering joists helps prevent floors from bouncing as you walk across them. The technique also helps shore up damaged or undersized joists. Either framing lumber or strips of 3/4-inch plywood may be used for the sister joist.

What is better for subfloor OSB or plywood?

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.

What is the best way to secure plywood subfloor?

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.

How thick should plywood be over subfloor?

The minimum thickness of plywood for subflooring is about 5/8 inch. Since it does not hold fasteners as well as plywood, OSB must be a little thicker, or at least 23/32 inch. There are several factors that determine what subfloor thickness is optimal for added benefits like insulation.

What are the best screws to attach plywood subfloor?

According to construction and renovation experts, some of the best screws for subfloor include the Senco 08200Y screws, the Simpson Strong-Tie screws, and the Hillman Group 48248 subfloor screws.

How far should a screw go into a joist?

The general rule of thumb is that the screw should enter at least half the thickness of the bottom material, e.g. 3/4″ into a 2 x 4. The other factor is the screw's diameter, or gauge. Screws come in gauges 2 through 16.

Why do framers use nails instead of screws?

Nails are often preferred for structural joining, including framing walls, because they are more flexible under pressure, whereas screws can snap. Nails are also called upon when securing plywood sheathing for exterior walls, installing hardwood floors, and attaching siding and roofing.

Does drilling holes in joists weaken them?

Holes or notches made in a joist will weaken it, avoid making them if possible, even if it means re-routing cables. If this is not possible please follow the requirements below. Note: Drilling or notching outside these limits should be designed by an engineer.

What size screws are best for plywood?

Wood Screw: #8 x 1-1/4"

This is one of the most common types of construction I do in the shop -- attaching a sheet of 3/4" plywood to a carcass made of 3/4"-thick lumber. The #8 x 1-1/4 screw is perfect for bringing these two boards together.

Is it OK to screw into the side of plywood?

* Nails, brads or screws won't hold in the edges of thin plywood. However, you can sink screws into the edges of three-quarter-inch plywood if you drill pilot holes and center the screws on the edge. * When nailing into face plies, space nails at four-inch intervals for maximum panel strength.

Do you stagger seams on a subfloor?

Underlayment panels should be installed with the long direction, or strength axis, perpendicular to floor joists, never parallel to the subfloor seams. All panel edges should be staggered at least 2 inches to the subfloor seams for increased stability.

Which side of plywood subfloor goes up?

Install plywood underlayment smooth side up. To avoid damage to the surface, install underlayment immediately before laying the finish flooring.

Does it matter which side is up on subfloor?

When installing sub-flooring, you'll want the rough side facing up as well for traction when working. This is especially true when you have OSB that has been treated with a sealant or moisture barrier. Moisture resistant resins can create even more slippery surfaces.

How many tubes of glue do I need for a subfloor?

TITEBOND SUBFLOOR ADHESIVE 28OZ (4 SHEETS SUBFLOOR PER TUBE)

Reduces the amount of nailing and helps eliminate squeaky floors.

Can you use liquid nails as a subfloor adhesive?

Liquid Nails gets the jobs done!

Liquid Nails LN-602 Subfloor and Deck Construction Adhesive is the perfect adhesive for subfloors, flooring and decking. It can be used inside or outside and all the extreme weather. LN-602 is perfect for bonding building materials such as wafer board, plywood, lumber, etc.

How far does a tube of subfloor adhesive go?

Coverage: One 24 oz. can of AdvanTech subfloor adhesive yields approximately 400 linear feet of gel adhesive as 1/2" bead compared to applying a 28 oz. cartridge adhesive at 3/8" bead yielding approximately 38 linear feet.

How do I keep my floor joists from rotting?

Removing moisture is the most efficient and effective way to stop deck joist rot, and ensure that your deck joists last for years. Fungi need moisture levels above 18 percent to grow. Therefore, keeping the joist's moisture level below 18 percent should prevent rot.

How can I make my subfloor stronger?

Apply construction adhesive to the subfloor before additional plywood is laid. each joist tightens the layers and reduces the chance of future squeaks. When fastening to joists less than 8 in. tall, drive two rows of 8d nails or 2-in.

What is blocking between joists for subfloor?

In joist blocking, an extra wooden piece is installed perpendicularly between two adjacent joists. This provides resistance against joists twisting which in turn reduces any bouncing of the floor. In joist sistering, an additional joist is installed just adjacent to a joist that is damaged.

What are the disadvantages of plywood subfloor?

Plywood tends to splinter, making it difficult to cut designs into your floor. You may also have to use timber or decorative mouldings to cover up the layers that are visible along the edges of your floor. While it has some water-resistant qualities, moisture will still weaken a plywood floor.

What grade of plywood is best for subfloor?

C-grade plywood should be used when appearance is not important, such as for subfloors or garages. D-grade is also unsanded with defects that have not been repaired and knot holes up to 2 1/2 inches across, discoloration and sanding defects.

Should I use pressure treated plywood for subfloor?

There's no need to worry about making treated wood safer that is completely covered in other materials and hidden from access, such as subflooring. Pressure treated wood doesn't release any gases or particulates that could harm you and your family.

Does plywood floor need expansion gap?

APA recommends a 1/8-inch space between panel edge and end joints. Plywood and oriented strand board (OSB), like all wood products, will expand or shrink slightly with changes in moisture content. If the wood structural panels are tightly butted, there is no room for expansion and buckling can occur.

Does subfloor need to breathe?

Wooden or plywood floors need to breathe, so look for an underlayment that allows this to happen. Cork is a top-of-the-line option that's natural, breathable, and feels luxurious. The right underlayment can also help with noise reduction and energy efficiency.

Should you put plastic under subfloor?

Subfloor Material

Therefore, because concrete is porous, it's a good idea to install a vapor barrier over your concrete subfloor before installing your flooring. This way you can stop the vapor drive of water upward to your floors, protecting them from any damage (source).

How far apart should tongue and groove plywood be?

The American Plywood Association recommends that T&G plywood sheets be spaced 1/16 inch apart at both sides and ends.

What is the minimum thickness of a subfloor?

A subfloor is the bottom-most structural level of your floor. A good subfloor needs to be durable, level, at least 1 ⅛ inches thick, and free from residue. If it is not, it won't support tile well. Even the smallest cracks or depressions in a concrete floor could cause your tile to break early.

Can you use cement board as a subfloor instead of plywood?

Cement backerboard is more stable than plywood in high humidity and other wet environments. It won't swell and buckle the way that plywood does, so it's safe to use in mudrooms and bathrooms where things like spills and puddles are normal, as well as in areas with high levels of moisture in the air.

How do you secure a subfloor to joists?

A thicker subfloor takes a 3-inch screw. Use a heavy-duty drill to drive Phillips head wood screws through the subfloor into the floor joists. Drive the screws approximately 8 inches apart. To make the job easier for you and the drill, we suggest that you pre-drill holes before screwing the subfloor down.

Do you nail or screw subfloor?

Screws are preferred over nails for subfloor and underlayment installations as they provide strong and tight connections that help prevent the floor from squeaking. Before starting your next subfloor or underlayment installation, make sure you have the right subfloor screw gun for the job.

Does sheet flooring have to be joined on top of a joist?

boards should be glued to the joists and the sheets glued to each other with polyvinyl acetate (PVAc) adhesive (not softwood boarding) long edges at room perimeters should be fully supported on joists or noggings.

Do you have to use tongue-and-groove plywood for subfloor?

You can use standard plywood for subfloors, but it is more common to use tongue-and-groove sheets that interlock along the edges. The spacing of the joists governs the recommended thickness of the plywood subfloor.

Does the smooth side of OSB go up or down on a floor?

OSB also has stamping that reads “This Side Down”. This directs the worker on the correct orientation of the board when installing. The side with the stamp is the smoother side. When installed smooth side down, the rough surface will then face up and give the worker traction for safety.

What is the expansion gap for plywood subfloor?

To avoid buckling, subfloor panels should be spaced with a 1/8-inch gap at all edges and ends to provide room for naturally occurring expansion.

Can you board straight onto joists?

Can I Board directly onto joists? The simple answer is no. The most common joist heights in use in modern properties are between 75mm and 100mm.

Can you put floor over joists?

Wood Floor Fitting Over Joists

In general, they shouldn't be more than 45cm apart. If the gap is bigger than this, it's possible to use noggins and braces for support or simply install a plywood or oriented strand board subfloor first before laying the top floor. Truth be told, having a subfloor is just better overall.

What is the subfloor on top of joists?

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.

What size nails do I use for 1 2 inch plywood?

Make sure that they are 12-gauge or thicker. As a rule of thumb, the length of your nails should depend on the thickness of the plywood or sheathing.

How do you sister a joist with plywood?

For sistering, cut ¾-inch plywood into long strips the same width as the joist's web. Glue them to both sides of the web and nail with 4d or 6d nails. Make sure to stagger the end joints on either side of the web. The more layers of plywood, the stiffer the joist, but it's time-consuming and costly.

What type of glue is used to bond plywood to the floor joists?

Titebond Solvent-Based Subfloor Construction Adhesive is a professional strength formula that is specifically designed for subfloor installations and general plywood use. It provides a permanent bond that remains flexible, reduces nailing and prevents squeaky floors.