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How Do I keep Moisture Out of My Storage Shed?

How Do I keep Moisture Out of My Storage Shed

You’re storing some valuable things in your storage shed and one day you find moisture, condensation and high humidity in your storage building. A storage shed is an investment and you certainly don’t want moisture in it.

To keep the moisture out there are some steps to take, waterproofing the exterior of the shed will keep moisture out from the elements. Insulating and installing a vapor barrier will help, if humidity is a problem, you can add some ventilation which will also help with dampness and condensation issues.

Why you Need to Keep Moisture Out

The biggest enemy for storage buildings is moisture, and if left unchecked it can lead to condensation, humidity and mold. If you have a wood constructed shed it can begin to rot and the dampness can damage the contents in the shed. Even if you live in hot dry climates it’s a good practice to keep moisture out of your shed.

Ryans Shed Plans

Checking For Moisture and Leaks

Begin by visually inspecting for leaks inside during rainfall and then do a walk around and look for any visible spots that water can enter. The usual telltale sign of leaks is water inside the storage building or a musky smell.

Finding areas that are damp, and if it’s a wood shed there may be areas of staining where the water is entering. If you do your inspection during a rain storm you’ll be able to see where the water is getting in. Remember that water signs inside may be coming from condensation and not an actual leak.

During your inspection look for oblivious damage to the shed such as rotting wood near the floor or maybe moisture is entering thru the floor. If there’s rot and water entering thru the floor you’ll need to repair these issues.

Waterproofing Your Shed

If you’re going to be building a shed follow these 3 steps first:

Step 1] Location… Choosing a good location is vital to keep moisture out of your shed. Don’t build your shed in areas that are subject to water pooling, low lying areas. Find a location that will receive some sunlight ensuring that any rain will evaporate which helps prevents any leaks.

When choosing the location do a walk around after a rain to see which areas in your yard are still moist and damp, try to find an area that the ground has dried out quickly.

Step 2] Build Above the Ground… Building you shed off the ground will certainly help with moisture and dampness inside the shed. When building make sure the type of foundation your using will allow the shed to be higher than the finished ground level, keeping it at least six inches above the ground will really help with moisture issues. Read my article How High Should a Shed Be Off the Ground? for ways to prevent moisture and rot from destroying your shed.

If you’re going to construct the shed on an existing driveway use pressure treated lumber for the bottom plates. Another advantage of building your storage building above ground is it allows some air flow to help deal with moisture and condensation.

Step 3] Correct Foundation… Choose a foundation type that will keep the shed up off the ground, a good choice is pressure treated beams and a treated wood floor. This foundation will protect the shed from any ground water or moisture from entering from the ground.

If you have a large shed to build another method to keep moisture out is using piers, that’s concrete solo tubes sunk into the ground and then you add the beams and build the floor and shed. This foundation will also ensure there’s no movement from frost if you live in an area that has cold winters.

Shed Plans

Waterproofing Your Shed if Already Built

If you have an existing storage building that has moisture and dampness and leaks already there are several options that you can do to keep the moisture out.

Option 1] Install Drainage Around the Perimeter… You can install some drain rock around the outside and direct the water away from the shed. What I have done is added some gutters to the roof and using downpipes directed the water away from the shed. You can also use rain water barrels to direct the water from the roof into the barrels. For more information read my article What’s The Best Way to Add Drainage Around a Shed?

Option 2] Seal the Shed’s Base… Depending on what type of foundation your shed has you can add some galvanized flashing and seal with a good quality caulking or some roofing tar underneath the flashing.

You can also caulk the interior of the sheds floor plates to help stop water from entering. If you have a metal shed there is usually a channel that connects to the base and it can get filled with water and cause rust and mold to form. Sealing the channel from the outside with a clear silicon caulking can prevent water from entering.

Option 3] Keep Outside of Shed Clear… To help with natural air flow around the sheds base be sure to cut away any grass or other plants that have started to grow there. Be aware that roots from nearby trees can be allowing ground movement and letting water enter. Avoid having plants like ivy as they can do a lot of damage to the shed, its wise just to not have anything planted around the exterior of your storage building.

Waterproof Your Shed as Your Building It

The best time to take measures to keep moisture out of your storage building is while you’re building it. When using the right materials and correct installation practices and finishing the exposed materials with the right water proof material will give you a shed that will resist moisture, condensation and be a safe and secure place for storage.

Step 1] The Floor… Weather your building your own storage building or using a pre-fab kit the floor needs to be strong and very resistance to moisture. I recommend you use pressure treated ties and then use treated lumber for the floor joists and treated plywood for the floor deck.

By using treated lumber that’s made for wet conditions your floor will be resistant to rot and mold. Get a small can of wood preservative and apply it to any pieces of the treated and pressure treated lumber that you have cut and coat the exposed end with the preservative. It’s also recommended to use a vapor barrier, read my article Do I Need a Vapor Barrier Under My Shed? for more information.

Step 2] The Walls… Nearly all built storage buildings use OSB for sheeting in the outside walls, which is fine just don’t plan on leaving it as the exterior finish. Left unfinished OSB will absorb moisture and become damp very quickly which will encourage the growth of mold.

Be sure to use a building wrap or a tar paper over the OSB before installing your finishing product they are designed to protect the sheeting from moisture and greatly help to prevent the growth of mold and condensation from forming.

Ryans Shed Plans

Step 3] The Roof… The roof is going to take the brunt of the weather, so it’s important to choose the best type of roof and slope that will repel water away from the walls. Choose a gable or lean to type roof and use a minimum of 4/12 for a pitch, it will be easy to work on and will drain water away fast.

Be sure to use eaves protection under the shingles and make sure you have an overhang to direct water away from the sheds foundation. The typical eaves protection is twice the overhang but at least 3 feet if there’s little overhang. If you’re going to be using a metal roof apply a layer of 15 pound felt to the sheeting first. You won’t need eaves protection if you use the felt and metal roofing.

Other Things to Do to keep Moisture Out

Number 1] Re-Direct Water… Install gutters and downpipes to direct the water from the roof away from the structure. Be sure to attach the gutters right and lower at one end where the downpipe will be, use a short piece of downpipe or a roll up extension that will move the water away from the foundation.

Number 2] Weather Stripping… Doors and windows and known to let moisture in, especially doors that don’t close property and weather stripping that are worn out. Begin by inspecting any windows and use a good quality caulking and seal the window frames, sills to keep moisture out.

Invest in a good weather stripping and replace the old worn out one on the door, also make any adjustments to ensure the door is opening and closing correctly, that way any rainwater hitting the door will not be allowed to come in making your storage building damp inside.

Number 3] Insulation… This is a great option for keeping moisture and condensation out of your shed. It also helps keep it warmer in the winter. If you choose to insulate your shed make sure you apply a 6mm vapor barrier over it. You’re going to need to install some type of interior finish over it to prevent damage to the vapor barrier.

Number 4] Ventilation… Having good air movement is vital to avoid moisture and condensation inside the shed. If you shed is unfinished inside then a couple of gable vents, one on each end will allow for air movement from the soffit out the end vents. You can also install a couple of vents in the roof while installing the roofing.

There are some good options of solar powered vents that are powered by the sun and will circulate the air without needing electricity. You can see Amazons full line here.

Number 5] Paint or Stain Exposed Wood… Another easy way to keep moisture out of your storage building is applying some stain. If your using wood siding I recommended you apply a couple of coats of exterior stain. If you want to have a more wood look use a semi-transparent latex stain. If you want the color to be rich use a solid color latex stain.

If you really want to paint it, you’ll need to apply a coat of exterior latex primmer sealer made for wood. And then apply 2 coats of an exterior latex paint in the color you want, if your using cedar siding don’t paint it, use the stain or another clear wood sealer made for cedar. Cedar needs to breath and you’ll have nothing but problems if you paint cedar.


It will be a bit of extra work waterproofing your storage building, but once it’s done you won’t have to worry about moisture, condensation and dampness damaging your possessions and your storage shed will give you years of service. Thanks for reading and if you found it helpful, give it a share.