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How Do I Strengthen My Shed Floor?

If you’re planning on storing heavy tools or lawn equipment in your shed, you’ll want to have a strong solid floor. Or maybe your shed floor is already soft and sinking in places, either way you’re going to need to reinforce the floor.

First, reinforcing the floor joist, flooring material and in some cases the foundation will be necessary to strengthen the floor so it can support the weight of anything you plan on storing or using in it.

You know what kind of equipment and items you plan to store in the shed and how you intend to use it, so you need the floor strong to handle what comes along. Doing your best with the three elements will strengthen the floor.

How Far Apart Should Floor Joists Be for More Strength?

The floor joist spacing is not the place to skimp, as the joists help support the whole shed and everything that will eventually go in it, including yourself. While some people state that 24 inches apart on center is fine, the usual recommendation is 16 inches. If you plan to store heavy items or you are using something like plywood for the flooring, you might go to 12 inches.

This will help keep the plywood from squeaking as it tends to do. However, don’t make the mistake of thinking you can use thinner flooring as long as the joists are closer. You want your shed to last, and each element of the shed should be geared to that. For more information on floor joist sizes and spacing read my article What Size Floor Joist Spacing Should You Use?

What’s the Strongest Shed Floor Material?

The strongest floor material for a shed is undoubtedly the concrete slab. Many people who pour a slab for a foundation use it for the floor as well. The downsides include the fact that concrete slabs get cold during winter, so if you plan on spending a lot of time in your shed, such as using it for a workshop, your feet will notice the cold.

Standing on concrete for lengths of time also will make your feet ache sooner than other floor coverings. Using a rubber mat or two in places where you usually stand while working will help with this.

One of the most common and the next strongest is a pressure-treated wood plank floor. It can be painted or stained or left to its natural look. Some people use recycled barn wood for a more rustic look. Using tongue and groove planks makes the flooring even stronger. It can withstand a lot of weight without bouncing, shifting or squeaking.

Nails can be countersunk using a nail punch to keep nail heads from sticking up. While pressure-treated wood is more resistant to moisture, it certainly isn’t waterproof. You’ll need to be careful to shut your shed door when it’s going to rain or you risk getting the wood near the doorway wet, which can lead to staining, rotting and warping.

Even dripping yard equipment or muddy boots can affect the wood. A polyurethane coating will help with this problem. Even with the coating, it’s still to keep the door closed during rain.

The other two common choices are Oriented Strand Board (OSB) and plywood. In terms of strength, the OSB may be a little stronger when compared with the same thickness of plywood. It does need a little extra care in installing. The type best suited for shed flooring is recommended as class OSB3, which is made with glue that is resistant to moisture and dampness. You can get more details on flooring types in my article What Are the Strongest Shed Floor Materials to Use?

Resistant doesn’t mean waterproof, however. OSB can be affected by moisture and it’s not very easy to paint if you don’t like the look. It takes stripping off the wax coating the surface often comes with and uses several primer coats. Polyurethane coatings may also be used on OSB, but like paint, the OSB absorbs it up to a point, so do be sure to buy more than you think may be necessary.

The other thing that must be addressed is that any cut edges are susceptible to moisture and can swell. These should be treated with a moisture-resistant chemical. There are even sheets of OSB made for flooring that have interlocking edges but are more expensive.

To prevent the sheets from moving when weight is placed on them, the sheets ideally should have supports all along the edges, which means cross pieces inside the joists where the sheets will meet.

Plywood may be the most popular flooring, but even if you get the pressure-treated type, it will deteriorate over time. It is also prone to chips and gouges. Make sure you get a heavier grade to keep it from bowing or bouncing with heavy loads. A polyurethane sealant will help with the moisture problem but won’t solve it entirely, especially with the scratches and gouges the flooring will ultimately suffer during use.

How Do You Make a Shed Floor Stronger?

Basically, you make the floor stronger by constructing it with a sturdy frame and joist system, a good deck or floor that will withstand the type of use you plan to subject it to, and perhaps a floor covering over the basic floor that will absorb your kind of stresses, which includes paints and sealants. Other choices include linoleum and cushioned vinyl. If your shed floor is sinking read my article How to Lift a Sunken Shed Foundation? for more details on lifting and supporting your floor.

Should I Paint My Shed Floor?

You can paint your shed floor, but depending on how much traffic it will get, it may not be such a good idea. Remember, you’ll be storing tools, paint cans, etc. In short, there will be a lot of metal touching that paint, and it may scuff before you know it.

However, if you have a concrete pad and are using it for the floor, there are epoxy floor coatings. They are designed for garage use, so you know they will hold up in a shed. There is also concrete paint available. While both these products may seem pricey, remember that they are designed both to stick to concrete (which normal exterior paint has a hard time doing) and last through wear and tear.

If you’ve ever seen concrete painted by somebody who wanted to save money, you know how soon regular house paint starts to chip off. Also, you don’t want to have to clear out the shed every few years to repaint.

If your shed floor is wood or plywood, Kilz offers an enamel paint that is designed for wooden porches and patios, and therefore puts up with a lot of traffic. It’s designed to resist peeling, cracking, scuffing, and fading. It also has mildew prevention properties and dries within an hour and can be applied with paint rollers. A lighter color will make it easier to find errant screws or other small objects that fall down in the worst places.

These are easy to install over plywood. Besides protecting your floor from moisture problems from rain or wet equipment, it also provides a little more give in your flooring, make it more comfortable to spend a lot of time in your shed.


There is always putting another layer of plywood over the existing floor which will give you the extra strength. It’s always a good idea to make sure you have a strong foundation and joist system while building your shed to ensure a strong floor. If you need more information on strong shed foundations check out my article What’s The Best Shed Foundation Option For You?