You’re going to build a shed for yourself. You’ve decided on the foundation you want to use, but now you also have to plan for a floor. Of course, if you’re planning on a concrete slab foundation, you may just want to use the concrete for a floor.
Even those who use paving slabs for a foundation sometimes choose to just leave that for a floor if the climate conditions aren’t very humid and there doesn’t seem to be much need to have a raised shed.
If you are buying a pre-built shed, it doesn’t necessarily mean that you’ll automatically have a floor, as not all of them come with a floor, especially the plastic sheds. So, what do you choose for your shed floor?
Deciding on the type of flooring for your shed will depend a lot on its use and if you’re going to be storing heavy equipment in it.
Is OSB or Plywood a Better Flooring for a Shed?
Actually, OSB, or oriented strand board and plywood are second cousins to each other. They both are made by fastening wooden pieces into a solid form. Plywood is made by gluing thin sheets of wood veneer together, with the layers alternating as to the wood grain direction.
Both OSB and particleboard are made from wood flakes or chips oriented to make for an alternating grain pattern for strength. The only difference is that OSB is made from larger chips or even strips, while particleboard has much smaller pieces. Even sawdust may be included.
Which one you should choose, OSB or plywood, is debatable. OSB is more commonly used, as it is usually priced at a cheaper cost than plywood. OSB is also available in larger sheets, leaving fewer seams in your shed floor.
They both feature similar strengths and the ability to hold fasteners such as nails or screws. OSB is thought by some to have more shear strength or ability to span distances than plywood of the same thickness.
How Thick Should Plywood Be for a Shed Floor?
You want your shed floor to be sturdy and not to sag or bounce when you walk over it. In addition, many sheds will be used to house heavy items such as snowmobiles or riding mowers, so a sturdy floor is called for. Plywood used for shed flooring is usually 3/4-inch thickness.
How Thick Should OSB Be for a Shed Floor?
Even though OSB can span greater distances than comparably thick plywood, your joist placement and distance will play a part in how sturdy your floor will be. That being said, OSB is usually 5/8-inch thick for a shed floor.
One thing you need to consider when thinking about a possible OSB floor for your shed is moisture problems. If you live in a humid area or your shed is to be situated in an area that might stay damp a large part of the time, you may not want to use OSB as your shed floor. It can cause problems even when your shed is raised off the ground to allow airflow.
The problem with OSB and dampness is that OSB is more susceptible to moisture. While plywood will expand evenly over the board when it gets damp or wet and it dries quickly, OSB will absorb moisture more quickly on the edges. These edges can swell up as much as 15 percent, leaving you with a bunch of raised seam edges in your shed.
These swollen edges hold the moisture and can transfer it to your wall studs or sill plates. Not only will moisture cause the OSB to eventually deteriorate, but this transferred moisture can cause problems with your other wood as well.
This is something that must be considered before you make your flooring choice. Your local supplier can help you, as he should be knowledgeable as to whether your local climate is suitable for an OSB floor and what you need to do to protect it if you do choose OSB.
One thing that may help is to choose tongue-and-groove style OSB. This type has tongues on some of the edges which fit into grooves on the next panel, forming a connection that is sturdier and more resistant to moisture than two smooth edges butted up against each other.
Using Wood as Flooring for a Shed
While it may seem to be a bit expensive to use actual wood planks for your shed floor, there is another option. If you’re one of those lucky people who know of an old barn or other outbuilding being torn down nearby, you can reclaim the wood for your shed floor.
In fact, if you offer to help in the dismantling, you may be able to score the wood for free, or at least enough of it for your shed floor. Depending on the age of the building, you may get some really nice wood such as maple, chestnut, ash or even cypress without the high price of buying this wood new.
Carefully inspect your reclaimed wood for any bad or rotten spots or signs of termites, especially on the ends of the boards. Wood cracked lengthwise can also be salvaged if the crack is short enough so that it can be cut off and still leave a usable length.
You can always cut off the bad ends without spoiling anything. Also, discard any planks that are curved or warped from moisture. Sand off any splinters, but you can leave a rather rough finish. This will add to the antique look as well as provide a rougher finish and better traction for walking.
Waterproofing can be done using waterproofing stain or transparent polyurethane that is applied before laying down the flooring. Some people prefer using boiled linseed oil or tung oil. With oil, you need to thoroughly coat your boards, then let them dry for at least 30 minutes.
The oil will slowly seep into the wood. Then add another coat for a sealer. If the oil still soaks in, you may need another coat. Be sure to let the oil dry thoroughly before adding another coat.
You nail down the boards on the joists as you would any flooring. The waterproofing will bring out the grain and attractive features of the wood as well as protect it. You may just be surprised at how good it looks once it’s down as flooring. If you have some wood leftover, you can make a workbench or picnic table from it. Check out my article What Are the Strongest Shed Floor Materials to Use? if you need a really strong floor.
Should Flooring for a Shed be Treated?
When planning your shed, you need to think about how you will use it, not just now but in the future. Inevitably, you’ll get more yard equipment or “toys” as the years go by, so plan for possible future uses as well. You need to think about things such as how you’ll be tracking in water, mud and even snow at various times of the year.
Your flooring for a shed needs to be able to shake off the moisture and dry quickly, especially in the winter when your shed will be left open for far less time than in the summer. Since your shed flooring will take the brunt of the abuse you and your equipment and tools will shell out, you can’t be too careful with treating or waterproofing your floor.
Plywood for your flooring should definitely be pressure-treated. Since there are different grades of pressure treatments, explain to your supplier that your plywood is to be used as flooring for a shed and ask what grade of pressure treatment he recommends.
A waterproofing material used and allowed to cure properly will also help a great deal. Plan out any cuts you’ll need to make in the plywood panels ahead of time so you can apply waterproofing to the cut edges as well as the rest all at once. If you don’t, you’ll need to do it later after you’ve already waterproofed the uncut panels.
OSB does use a resin adhesive to form the boards that is heat cured, but it certainly doesn’t make the OSB panels waterproof. There is a grade of OSB that is waterproofed, but you’ll also need an additional waterproofing substance for the edges.
Any time you make a cut in an OSB panel, the waterproofing is gone from that edge. Since the edges of OSB are the most affected by moisture, you’ll want to make sure that you apply waterproofing to all the cut edges of your panels.
The best way is to make all the cuts in your OSB panels that you need, then apply the waterproofing substance, and give it the proper amount of time to cure before actually installing the panels. Make sure you have a dry place for the panel edges to cure in a place where they won’t get dirt or dust on the wet waterproofing. Placing them flat on some sort of rack or sawhorses in your garage would be a good idea.
What is the Best Floor Joist Spacing for a Shed Floor?
This is a subject of much debate. However, since your shed floor will take more abuse and support more weight than most places in your house, it makes sense to give it all the support you can.
While some sources say you can space joists up to 24 inches apart, for a sturdy floor, 16 inches apart is best. It’s much better to place joists a bit closer than you may think you need to than to find out that your floor isn’t up to the task after it’s too late to do anything to change it. Get more information about joist spacing in my article What Shed Floor Joist Spacing Should I Use?
How to Fasten a Shed Floor?
You may decide to use glue on the joists to make your floor more steady. Put glue on the required joists before fastening down your first flooring sheet, then put glue on the next floor joists that go under the next sheet.
This will prevent your glue from drying too soon as it would if you put glue on all the joists at once. Another consideration is the fasteners. Does one use nails or screws to fasten down the flooring for a shed? There are pros and cons to each. Need more information on what to use to fasten the plywood to the joist? Check out my article Do I Use Nails or Screws for Attaching Plywood?
The Pros of Nails:
- Nails are usually less expensive.
- They are also quicker and easier to install, especially if you happen to have a nail gun available.
- They will have a cleaner look, as they can be countersunk a bit if needed to hide them. You may need more nails than you would screws, as your need to space them more closely together and it’s easier to bend a nail if using a hammer than it is to bend a screw during installation.
The Cons of Nails:
- There is more risk of damage during installation, especially if you are using a nail gun and are new to handling one.
- The metal will wear out more quickly due to corrosion unless you get nails that are specifically corrosion resistant. Remember that you’ll be tracking water and mud over your floor and your nails will get some of it. Using galvanized nails will help this.
- If your floor joists are too far apart or your flooring is not thick enough, your floor may get a bit bouncy. This can slowly work some of the nails up over time.
- If they are long enough, they may not actually come out, but you don’t need a small nail head sticking into your lawn tractor tire or your small child tripping over a nail sticking up.
The Pros of Screws:
- Screws tend to be more durable using nails if you install them with an electric drill.
- They usually will cost less per pound, making them cheaper to use.
- It’s a lot easier to take out a screw than it is a nail if you make a mistake.
- Screws are also less likely to work out of the flooring over time, which makes them better at keeping your shed floor from getting squeaky.
- You’ll usually use fewer screws than you would nails, as nails should be six inches apart while screws only need to be eight inches apart.
The Cons of Screws:
- Using screws may lead to more humidity, which can eventually lead to rot or mold growth over time, especially on wood floors.
- It is more important to measure screws spacing out correctly, as using screws tends to mess up the spacing between boards if you’re not careful.
Whatever flooring you use in your shed, remember to choose something that will fit both your usage and the climate. Install it carefully, and don’t skimp on the joist or fastener spacing. Keep in mind that your shed floor will take a beating over time, and it will serve you well.