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 of plywood faces out?

More commonly, you'll come across A/B or A/C. This means that one side of the plywood is Grade A and the other is Grade B or C. For most projects, these types of plywood will work because you can put the higher rated side facing out while the lower rated side is hidden facing in.

What side of treated plywood goes up?

When CDX plywood is used as roof sheathing, the C side of the plywood is placed up, where it will be covered by roofing felt and then shingles. This leaves the D side facing down, into the attic, where it will most likely be seen.

Does it matter which way you run plywood?

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.

Is plywood strong in both directions?

Plywood is an assembled product comprising thin layers of wood bonded together with the grain direction of adjacent layers at right angles. Wood is anisotropic - that is, its properties vary with grain direction. It is strongest when stressed parallel to the grain and weakest when stressed perpendicular to it.

Installing the Subfloor

Does plywood have a grain direction?

The meshing of the plies of the wood is done in a very systematic manner keeping in mind the direction of the grains of the individual plies. During the making of plywood, it is closely monitored that each ply that is placed on top of the other has a grain direction perpendicular to the one above and below it.

Should plywood be installed with the grain running in the same direction as the floor joists?

Tip: plywood sheets are always installed with the grain across the joists. Spanning ratings for plywood and OSB are based on this assumption. Stagger adjacent sheets so that they do not start on the same joist.

How should plywood subflooring not lay?

Improper spacing.

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.

Does plywood have a face?

Plywood is made from thin layers of timber that have been rotary peeled from a log and then glued together, typically with the woodgrain of each layer at right angles to adjacent layers that enhance its structural integrity. The finished sheets are graded according to the appearance of the two veneer faces.

What do the lines on plywood mean?

These thin layers, also called plies, are glued together in alternating right angles to create a cross-grain pattern. This pattern adds strength and stability that resists shrinkage and expansion caused by moisture. Plywood is a popular choice in construction because of its strength and low cost.

What plywood is smooth on one side?

Sanded Pine - With its clean, smooth surface (one or both sides), sanded pine is perfect for building project boxes and cabinets.

Is OSB better than plywood?

Wood fiber is used more efficiently in osb. Osb is stronger than plywood in shear. Shear values, through its thickness, are about 2 times greater than plywood. This is one of the reasons osb is used for webs of wooden I-joists.

Can OSB be used as subfloor?

Most local codes allow OSB to be used for subflooring. It's always best to check with your local permitting office before using OSB for your subfloor. One advantage that OSB has over plywood is its larger formatting. For plywood, 8-foot and 10-foot long sheets of plywood are standard.

Should OSB be installed vertically or horizontally?

If the height of a wall is less than 8-feet, install the plywood (or OSB) vertically. If the height of a wall is greater then 8-feet, install the plywood (or OSB) horizontally.

Should subfloor be parallel or perpendicular?

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.

Does subfloor need to be tongue and groove?

For subflooring, you use tongue and groove plywood. The tongue and groove are only along the 8 foot edges. On the four foot edges, your seams will fall on joist tops, so no need for tongue and groove. But to start off, we will need to remove the tongue so the plywood is tight with the exterior ICF walls.

Which direction should wood flooring run?

The most common way to lay hardwood flooring is by aligning the planks parallel to the longest wall. Apart from a few exceptions like sagging joists, this is the preferred direction to lay wood floors because it aesthetically provides the best result.

Which way should the grain run in a drawer bottom?

Unless it's plywood, grain must be oriented laterally across the drawer opening so that endgrain rides in the side of the drawer. Fixed in the front, it will expand toward the back of the cabinet. Oriented the other way, the drawer bottom will expand sideways and the drawers will wedge shut in humid seasons.

Why are there an odd number of layers in plywood sheeting?

There is usually an odd number of plies, so that the sheet is balanced—this reduces warping. Because plywood is bonded with grains running against one another and with an odd number of composite parts, it has high stiffness perpendicular to the grain direction of the surface ply.

Why do you stagger plywood?

The end joint is where one board or plywood sheet butts up against another. In almost every situation, it's important to stagger these joints to avoid straight lines that extend in a perpendicular direction across the lengths of the boards.

What goes on top of subfloor?

Underlayment: Some types of flooring can be installed directly on top of the subfloor, such as vinyl flooring. Other types need a middle layer, called underlayment, such as laminate,carpet and tile.

What size plywood should be used for a 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.

How much load can 3/4 plywood support?

A 12-by-36-inch piece of 3/4-inch fir plywood can easily support 50 pounds. However, a 12-by-36-inch piece of 1/4-inch thick plywood will not support that much weight. It will only support about 5 pounds before bending.