Many people who build a shed choose 3/4 plywood for the flooring because of it strength and ability to hold up under a lot of weight. It’s fairly easy to work with and the large sheets cut down on the amount of work it takes to install. In addition, even though it will absorb some moisture, such as from muddy shoes or wet lawn mower tires, plywood tends to spread the moisture out, causing it to evaporate and dry more quickly.
A sheet of 3/4 plywood using 24-inch center floor joists can hold 170 pounds per square foot, you can increase the capacity by using 16 inch or even more by using 12 inches on center floor joists.
3/4 plywood is often recommended for use as a shed floor. Thinner plywood, such as 1/2-inch-thick plywood, can be used as a subfloor, but if you’re using the plywood as your main flooring, it should be thicker. As far as weight, depending on the type of wood used in the manufacture of the plywood, a sheet can hold 50 pounds of weight.
How Far Can 3/4 Plywood Span?
When you’re planning to install plywood flooring in your shed, one consideration is how far apart your floor joists should be. For plywood used as flooring, the maximum span is usually considered to be 24 inches. When the plywood is used in shelving, this distance increases to 30 to 36 inches.
Most floor joist spacing is recommended to be at 16-inch centers. This will greatly strengthen the floor as a whole and help your plywood floor do its job. Installing the plywood in the correct direction also increases it strength, check out my article What’s the Correct Direction for Installing Plywood? for more information.
How Much Does a Sheet of 3/4 Plywood Weigh?
This varies by the type of wood used to manufacture the plywood. The number of actual plies or layers used in the manufacturing process actually does little to affect the weight of the sheet. The common four-by-eight-foot sheet of 1/2-inch plywood will weigh 40 pounds when made of softwood, 45 pounds when made of hardwoods. The 3/4-inch softwood sheet will weigh about 60 pounds, while using hardwoods increases the weight to 68 pounds.
The formula for calculating the weight used by the American Plywood Association estimates that a sheet of softwood plywood should weigh around three pounds per square foot per inch of thickness. Using this formula, you can approximate the weight of partial sheets. Most plywood purchased is made of softwood.
Hardwood plywood is usually used in finishing carpentry projects in home interiors, such as furniture and cabinetry. Despite its name, hardwood plywood often contains some softwood in its manufacture as well.
What is The Strongest Type of 3/4 Plywood?
Marine plywood is the strongest type of plywood available. The manufacturing process uses high-quality glues, which not only keeps the plywood sound structurally but also makes it resistant to moisture. As its name implies it’s used in the construction of boats, docks, and waterfront buildings. It’s also useful as a subflooring for rooms likely to have water on the floor at times or an unusual amount of humidity in the air such as bathrooms and basements.
Of course, marine plywood is about the most expensive plywood you can buy. Another feature that adds to the cost is that marine plywood is usually only available in A-A grade. The letter grade refers to the outer finish from A to D. The A grade is the best, being free of knots and other defects.
It is usually reserved for furniture building. The other letter ratings allow for more imperfections as the letter goes to D. Plywood can, and often does, have different letter grades on the two sides, with the better side being used as the visible side. Of course, the better the grade, the more expensive the plywood. Another option is using pressure treated 3/4 plywood for your floor, you can get more information in my article Is Pressure Treated Plywood Best for a Shed Floor?
Will 3/4 Plywood Make a Strong Floor in a Shed?
Actually, this thickness of plywood is one of the most often recommended types for a shed floor. Of course, the closer the spacing of your floor joists, the more support you’ll have for your plywood floor and the more weight it will hold. We’ve previously calculated how much weight plywood can hold with floor joists no more than 24 inches apart, but the usual recommendation for shed floor joist spacing is 16 inches apart.
You need to remember that your shed floor will be asked to hold quite a bit of weight which will stay there for a significant period of time. Besides heavy lawn machinery and adult toys, you’ll use the shed floor for storage of heavy things such as large containers of paint, bags of fertilizer, and perhaps things such as storage of lumber scraps and metal parts.
If you’ve ever lifted a full five-gallon bucket of paint, you have a good idea of how much your flooring is being asked to hold. It just makes sense to keep your joists spaced together more closely rather than farther apart.
Pros and Cons of Plywood Floor for a Shed?
Pressure-treated exterior-grade plywood is the best type to get for your shed floor. This type will resist moisture, although it’s not completely waterproof. There are some pros and cons to using plywood for flooring, as with any material.
- Plywood can absorb moisture, but the moisture tends to spread out through the sheet, enabling the moisture to more quickly evaporate and the plywood to dry. Check out my article What’s the Best Way to Waterproof Plywood? for options to prevent moisture.
- Plywood is much more economical than some other types of flooring. It’s also easy to work with, both in cutting and fastening, and it’s easy to replace a damaged part.
- If you should decide that you want to add another flooring type, such as vinyl roll flooring, vinyl peel and stick tiles, or rubber matting, it’s easy to install over the plywood. Some people even use old carpeting to soften the floor if they plan to spend a lot of time in it, such as when doing woodworking, potting plants or repairing items. Carpeting, too, is easy to install over plywood.
- Plywood is flexible, meaning that your heavy yard tools rolling over it won’t cause problems. While the sheets won’t sag, they have enough give to adjust to those heavy weights.
- Plywood flooring is good for storing wet tools or tools with wet tires, such as snow blowers and lawn tractors, as it dries out quickly. Since it doesn’t undergo much expansion and contraction with temperature changes, it can work in both hot and cold climates.
- Plywood is easily painted, both to change the look and to seal it from moisture. This also helps prevent anything from scratching up splinters.
- Plywood is usually smooth enough to be easy to just sweep clean. If you’ve never owned a shed before, you may be surprised at the amount of dirt, leaves and tree debris that collects or gets blown inside over time.
- When plywood does get wet, although it dries more quickly than, say OSB, it will tend to swell until it dries out. This could potentially cause nails to be raised up if the swelling occurs at a joint. Even pressure-treated plywood can suffer when exposed to moisture long-term. If your shed is raised up a few inches to allow airflow underneath, this will help keep the underside of the plywood dry.
- If you find that you have some rather long-term dampness under your shed, or think that you may run into this problem, you might want to invest in a moisture barrier. Fortunately, heavyweight plastic sheeting comes in rolls of various widths and is fairly easy to install, even under an existing shed. Your joists will benefit from the extra protection as well.
- Plywood will have a knothole here and there, even if you purchased higher-rated sheets. Those letter grades refer to the grade of the two outside layers. The interior layers will still have faults. This won’t be a problem unless two or three layers have defects that happen to line up with each other, causing a potential weak spot.
- If you buy plywood in a cheap letter grade, meaning that there are visible knotholes on the surface, you need to be aware that these can actually pop out of the wood under the right circumstances. When sawing a sheet to fit, try to plan your cuts so as to keep away from the knotholes. They can pop out if you saw too close to them. Of course, it’s hard to see where a knothole may be on one of the interior layers, but just be aware of the problem.
- If the moisture stays a problem, such as in the case of a roof leak that isn’t discovered for a couple of days, this swelling could become a real problem. Plywood subjected to long-term moisture might start to actually deteriorate in some cases.
- Plywood is rather soft and can be scratched or gouged by a carelessly dropped pair of loppers or another sharp object. A dent or a minor scratch won’t be much of a problem in a shed, however, unless it messes up your paint job.
Plywood flooring is a popular choice for shed flooring, especially since stability and strength are more important than the actual appearance. You may not want plywood as the main flooring in your home, but for a shed, it’s a really good choice. Like any other material, if you get the right kind and take care of it, it will serve you for many years to come.