‘What size plywood for roof’ is such a common question for roofing installation. A lot of homeowners prefer to use plywood as the main roofing material.
Plywood has many advantages, including a beautiful and rustic look, greater flexibility in its usage, and a more affordable size. Find out information about the size of plywood for roofing below.
Understanding Standard Size for Roofing Plywood
When choosing plywood as a roofing material, you need to know the standard size for sure. However, you also need to figure out the thickness as well. For instance, due to its durability and moisture resistance, CDX plywood is a common choice for roofing. Figure out the answer of what size plywood for the roof and its thickness on this particular list.
Read also: Understanding Plywood Thickness for Roofing
1. The Standard Size
In most manufacturers and brands, plywood sheet for roofing comes in the size of 4×8 inches. This is like a very common size, and you will find many different types of plywood adapted to this particular size. So, the answer to the question of what size plywood for the roof is around 4×8 inches.
2. The Standard Thickness
The thickness of plywood used for roofing is critical. For residential roofs with rafter spacing of up to 24 inches, 5/8-inch plywood is the minimum required by most building codes. However, 3/4-inch plywood is advisable for added strength and stability in regions prone to heavy snow or wind loads.
In cases where rafters are spaced closer (16 inches), 1/2-inch plywood may suffice, though using thicker plywood can offer better long-term performance. Always match the plywood thickness to the load requirements of your roof.
If you purchase the 4×8 inches plywood, the thickness will be around 5/8 to 3/4 inches. It will all depend on the grade of the plywood. As we know, plywood grade is divided into four kinds: grade A, grade B, grade C, and grade D.
| Plywood Thickness | Rafter Spacing | Best Usage Scenario |
|---|---|---|
| 1/2 inch | Up to 16 inches | Lightweight roofs, moderate climates |
| 5/8 inch | Up to 24 inches | Standard residential roofs, moderate loads |
| 3/4 inch | Up to 24 inches or more | Heavy snow or wind areas, flat roofs |
As a roofing contractor with over a decade of experience, I’ve observed that homeowners often overlook the importance of plywood grade and thickness.
For instance, while 3/4-inch plywood is commonly recommended, many are unaware that local building codes sometimes allow a minimum of 5/8-inch thickness, depending on rafter spacing and roof load expectations. Using the correct thickness ensures durability and provides long-term savings on repairs.
The finer the grade, the thicker the plywood is. A-grade plywood sheet usually has that standard ¾ inches flat roof plywood thickness, suitable for handling a heavier load.
From my experience, especially with flat roofs, I have found that plywood thickness plays a crucial role in the roof’s longevity. Using at least 3/4-inch thick plywood for a flat roof is essential to prevent sagging and water pooling, which could lead to leaks and structural damage. I always recommend this to my clients when considering long-term roof performance.
3. Factors to Consider
These are some factors to consider when choosing the plywood size for roofing. Consider them before buying any plywood sheet.
- The Design of the Roof
There are two common designs for roofing: flat roof and steep roof. Each design requires different types of plywood sheets as well. The steep roof has to be filled with smaller plywood sheets with tighter gaps. The flat roof is great enough for the standard-sized plywood, and it requires regular gapping as well.
Read also: Flat Roof Types – Guide
- Rafter Spacing on the Roof
Of course, every roof has a rafter, and the spacing between the rafter and the roof determines the size of the plywood sheet. The closer the gap between the rafter and the roof, the larger the plywood size required to prevent leaks.
- Expected Roof Load
The roof will have a load at some points. Build-up snow, dirt, debris, and dry falling leaves will pile up and burden the roof. If this load is expected to be very heavy, select a bigger plywood sheet and the thickest one, especially if using CDX plywood for a heavier load.
Read also: How To Install Snow Guards
You know it is when to replace plywood on the roof if the burden is heavier and heavier.
Installing plywood on a roof might seem straightforward, but it requires precision and understanding of the material’s behavior under different conditions. During my years in roofing, I’ve noticed that improper installation can lead to premature failure, especially on flat roofs where water drainage is less efficient.
If the plywood isn’t aligned correctly, or if gaps are too wide, moisture can seep in, leading to rot. That’s why, even for DIY enthusiasts, I always recommend professional assistance, particularly for large or complex roofs.
When selecting plywood for roofing, it’s important to consider the local climate. In areas with frequent rain or snow, choosing a type of plywood like CDX plywood that can withstand a heavier load and moisture is crucial for the roof’s longevity.
For DIY enthusiasts, understanding the specifics of plywood, such as the advantages of CDX plywood in roofing applications, can significantly improve the success of their roofing projects.
To cover 1,500 square feet of roofing, you will need many, many plywood sheets. This is why, after understanding ‘what size plywood for roof’, you better call someone professional to do the installation.
