Can you add plywood to a roof?

As long as the new plywood itself can span the distance and carry the roof, wind, seismic and snow loads for your region, adding new ply over old is just fine. The new plywood thickness should be at least equal to the exusting plywood thickness.

How thick should the plywood be for a roof?

Most Common Thickness

The most common rafter spacing is 24 inches, and 5/8-inch plywood is recommended for that. It will support roof loads for most situations and is the standard for most roof applications. Roofs with very heavy loads may require 3/4-inch thickness.

How many sheets of plywood does it take to cover a roof?

Divide the total roof area by 32 to get the number of sheets you will need to cover the roof. A typical 4 foot by 8 foot sheet of plywood covers 32 square feet. If your roof area is 1,600 square feet, 1,600 divided by 32 will mean you need about 50 sheets to cover the roof. Add 10 percent to allow for waste.

What is under the shingles on a roof?

Roofing underlayment is what lies between the shingles and the roof sheathing, or roof deck, which is typically either plywood or OSB. It’s installed directly on the roof deck and provides a secondary layer of protection from the elements, including rain, snow, and wind.

What goes on top of plywood on roof?

When installing metal roofing, you should always use a roofing felt layer between the metal roofing and the plywood. It is also advisable to use a slip sheet to protect the felt. You may be able to layer it on top of your current roofing, but you need to check with your local building codes before doing so.

Can you put shingles directly on plywood?

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Quote from Youtube video: Which other roofing materials use roof shingles are actually installed over a plywood deck.

Can you use 1/2 inch plywood for a roof?

1/2 or 5/8 inch roof sheathing

The most common thicknesses for roof sheathing are ½ inch or ⅝ inch. Some older houses may have ⅜-inch roof sheathing, but this has been banned in many areas due to its fragility and your roofing contractor may have to replace it if you have it.

How much is a sheet of plywood for roofing?

between $70 to $100

Your price could vary depending on how much the roofing company charges for labor, but generally, you can expect to spend between $70 to $100 for each sheet of plywood. A 4 x 8 sheet of plywood covers about 32 square feet of roof area—and the average roof measures about 3,000 square feet.

What is the roof sheathing covered with after installation?

Unless otherwise recommended by the sheathing manufacturer, cover the sheathing with shingle underlayment felt to minimize exposure to weather.

Is roof underlayment necessary?

All roofs have underlayment. At a minimum, a roof with asphalt shingles should be completely covered with one layer of underlayment. Roofers may consider adding layers of underlayment for superior protection, which is especially useful on low-pitch roofs.

What is the wood called under a roof?


The sheathing is the layer of flat wooden boards that attach to your home’s rafters or trusses. The most common materials used for sheathing are plywood and oriented strand board (OSB). Roofers use a nail gun to secure individual panels down, making your roof into one cohesive unit.

What wood goes under roof shingles?

It’s essentially the foundation of the roof. This is typically made with OSB or oriented strand board or plywood that’s attached with nails onto the rafters.

What is skip sheathing?

Skip-sheeting, or spaced sheathing, is just as it sounds: sheathing with gaps between. Traditionally, skip-sheathing consists of 1 inch by 4 inch boards nailed to the rafters with gaps between the boards. Spacing between boards is optimal for wood shakes but cannot support asphalt composite shingles.

What are the layers of a new roof?

And when you do replace your roofing, there are three main layers that have to be addressed: the roof deck, underlayment, and the shingles themselves.

What goes on top of a roof?

Roof Ridge: The roof ridge, or ridge of a roof is the horizontal line running the length of the roof where the two roof planes meet. This intersection creates the highest point on a roof, sometimes referred to as the peak. Hip and ridge shingles are specifically designed for this part of a roof.

What does a roof consist of?

Roof covering: shingles, tile, slate or metal and underlayment that protect the sheathing from weather. Sheathing: boards or sheet material that are fastened to roof rafters to cover a house or building. Roof structure: rafters and trusses constructed to support the sheathing.

What are the three main components that make up a roof?

Structural Layers of the Roof

It incorporates joists, trusses, and rafters. Together, these three types of beams make up a framework that gives the roof its shape.

Will my roof break if I sit on it?

There are many potential hazards of sitting on your roof. While your roof is certainly designed to withstand many things, lounging is likely not one of them. Sitting on your roof could cause you personal injury, roof damage, or even structural damage to your home.

How much weight can the average house roof hold?

Modern roofs can hold up to 10 feet of snow or 20 pounds per square foot.

How do you tell if a roof is safe to walk on?

Roofing professionals wear soft-soled shoes and step carefully to avoid damaging your shingles. They know which areas of the roof they absolutely can’t step on, including the valley. If you step on into the valley with regular running shoes, or heavy work boots, you could create a leak.