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How Thick Should Plywood Be for Roofing? (Answered)

There are several roofing materials in the market. You choose the best material for yourselves. Roofing materials vary from place to place as the weather conditions don’t match in every place.

For roofing, plywood is also preferred. Let’s see what thickness of plywood is best for roofing.

How thick should plywood be for roofing?

Plywood is used for various purposes. It is widely used because of the lightweight and strongness of this material. Five to eight inches of plywood thickness is suggested. Any less than five inches in thickness is not a good choice for roofing. The roof takes the most pressure than any other place.

The size of the plywood may differ according to different shedding types. Let’s get to know about them.

Shed roof:

For shedding, most building developers use 15/32 inches of plywood. Mainly the CDX plywood is used as a shed roof. The thickness of the plywood should stay between 3 to 4 inches. CDX plywood is made as exterior grade plywood.

And it is lightweight and strong at the same time to be used as a shed roof. Make sure that the plywood is placed in a way that the snow or rain doesn’t stick there for a long time.

Flat roof:

For a flat roof, a minimum shedding of 18mm or less than an inch thickness is recommended. But it is for a regular rooftop. When you are making a roof using plywood, you will need at least 3 to 8 inches thick plywood.

There is no maximum limit for your plywood roofing thickness. People generally use 24 inches of rafter spacing and keep the plywood thickness to 5 to 8 inches.

Though 3 to 8 inches is the minimum requirement, the standard is 5 to 8 inches thick. The best plywood for a flat roof is OSB plywood or WBP plywood.

Can I use 1/2 inch plywood for shed roof?

Yes, you can use ½ inch plywood for the shed roof. Just while you use plywood for shedding, you need to ensure that the plywood is CDX type or T&G type.

Because this type of plywood is mainly made to use externally. Here CDX is used for external walls and roofing, which is waterproof and can take direct sunlight as well. The T&G plywood is better than the regular plywood, and it is costlier as well.

CDX plywood is famous as it is the best overall. For shed roofing, there are no other good competitors better than CDX and T&G plywood.

Also, ½ inch CDX plywood is considered to be the best material that has dimensional stability in it. That’s why contractors generally use ½ inch CDX plywood for roof shedding.

Is thicker plywood better for roofing?

It depends, on whether you are living and what is the weather condition of your place. The standard thickness of plywood for roofing must be 3 to 4 inches, while a minimum of ½ inches of thickness is needed.

Too much weight on the roof is not good for your home overall. The weight can eventually drag your ceiling down to gravity. That’s why using lightweight, but strong plywood is recommended.

Sometimes when you are planning to make an attic, you must need something strong and thick. Because it will have the ability to firmly hold your belongings on the top of the roof.

While roofing the best thickness can stay around 5 to 8 inches and the standard thickness of roofing plywood is mentioned earlier. As per your need, the thickness of your roofing plywood may vary.

Why thickness of plywood for residential roof important?

There are several reasons why the thickness matters. Let’s get to know.

To Ensure Proper Safety:

Mainly when you build a home for yourselves, you always ensure that the upper roof is strong. Whether it is a campsite or a short-term home for you, you must make a roof over your head.

So, it is the most important thing for you to keep yourselves safe from the direct sunlight, rain, snowfall, and other wild winds issues. A building without a roof will not keep you and your belongings safe from anything at all.

If you use thin plywood for roofing, it will not stand firm against any storm, snowfall, or anything at all. It will not be going to be durable.

Stay robust against any wild Wind:

Every area is unsafe due to the wild storms. Wild storms always have the wild wind with them. If you build a home with a thin layer of plywood, it will not stay firm against stormy winds.

Moreover, if somehow a tree falls on the rooftop, it may not hold the rooftop strongly. So, a robust plywood setup is required.

It can hold more Pressure and Weight:

When snow falls at a high rate, there is a high chance that the snow stuck on the roof. And we know, that when snow is stuck, it starts to form ice. Ice is heavier than water.

However, if your roof cannot hold the weight and pressure of ice or snowfall, it will eventually dent inside. That’s why you need thick plywood for a residential roof.

What type of plywood is used for roof sheathing?

You can choose from a variety of plywood for your roof. Let’s take a look at the list.

CDX Plywood:

CDX is the best plywood for roof sheathing. As it comes with the best dimensional stability of any other plywood. It can absorb water in no time, and it can be dry sooner than any other plywood.

So, the thickness remains the same for a longer time. It is used outside as it is less expensive, and it is the proper value for money.

T&G Plywood:

T&G plywood is also known as tongue-and-groove plywood. This plywood is superior in quality to regular plywood. It can be used as floor plywood as well as roof plywood.

It remains sturdy for a longer time than the regular plywood. As the cost associated with this plywood is higher, that’s why it is not used widely.

What thickness OSB should be used for roofing?

Generally, CDX or T&G is recommended for roofing. OSB plywood of 7/16 inches is recommended for roofing. Because OSB plywood is not as strong as the CDX plywood. There are several types of plywood, from them CDX is good for external usages.

And CDX is considered to be the best plywood overall. Basically, you can use OSB sheets of 7/8 inches where the snow load is higher or equal to 30 pounds per square foot. These sizes of OSB sheets can handle that much integrity and that’s why it is durable than other OSB sheets.

How thick does plywood need to be for the attic floor?

The attic is the hollow part between roofs. For the attic floor, you need to have plywood of 3 to 4 inches. At the first glance, you might want to use thicker plywood, but if you abide by the standard procedures, then 3 to 4 inches of plywood is perfect.

If you use ½ inches sheet for the attic floor, it may not have the strength to hold your attic perfectly. Basically, ½ inches sheet can be used in 16 inches spacing, while for 24 or more joint spacing you will need to have ¾ inches plywood.

What is the roofing plywood cost per sheet?

The cost per sheet varies. The best roofing plywood is CDX plywood or T&G plywood. Though T&G plywood is the best plywood for roofing, CDX is famous overall. Roofing comes with the cost of labor and materials.

Also, the better your drainage system will cost you more money as well. Moreover, the value of your roofing varies as per your materials.

Generally, it takes about $70 to $100 per sheet. You will need to spend $1050 to $1575 to cover a 2400 square feet home’s roof area. You’ll need to add more money with it for labor costing.

How many sheets of plywood do you need for a roof?

You can customize the plywood sheets if you want to purchase them in bulk. But your roof area is specific.

And the specified area needs a specific distribution of plywood. Let’s assume your roof area is about 2400 square feet. And if you buy a 4 by 8 feet plywood sheet, it will cover 32 square feet of your roof.

Then if you do some quick math by dividing 2400 square feet of an area by the sheet area of 32 square feet, you get the number of sheets you need, which is 75 plywood sheets for your 2400 square feet roof area.

So, as per your roof area, you can get the number of plywood sheets you need.

Final Thoughts

A minimum of 3 to 8 inches is needed to be a good plywood roof. But, if the roof thickness is less than 1 to 2 inches, then it is not recommended. The standard thickness is 5 to 8 inches. Plywood is used widely as it is less costly and can keep the perfect room temperature. It requires less money.