Your shed is an investment. If you want it to last for years, or even decades, then a waterproof shed is a necessity.
To fully waterproof a shed, first, make sure you select a good location for your shed, use the right foundation, build a drainage system, and remove nearby vegetation. Next, weatherproof the floor and walls, install siding, protect the roof, and properly add gutters. Finally, apply caulk, insulate the shed, add ventilation, and paint all wood surfaces.
While waterproofing a shed sounds like a lot of work, it isn’t as challenging as it seems. By following the steps below, you can handle the entire project yourself.
Why Waterproofing is Essential
For sheds, water is the enemy. Not only can it harm the structure, leading to rot and mold, but allowing water to seep in puts your contents at risk.
Wood is particularly susceptible to water damage. Even water-resistant species, like cedar, aren’t naturally waterproof. You need to take action if you want to keep rainwater from saturating the material.
Even if you live in drier parts of the country, water is still a threat. Every state and city gets at least some rainfall, and even small amounts of moisture can harm your shed.
How to Check Your Shed for Leaks
Before you waterproof your shed, you need to check for leaks. This lets you know if any damage or weak points exist, allowing you to address issues before you begin the waterproofing process.
Checking for Leaks
The best time to check your shed for leaks is after it rains. Typically, rain will hit most of the exterior surfaces, so you’ll be able to locate a wider range of potential problems.
Additionally, if you check right after the rain, the water might not have fully evaporated. If you wait too long, you may miss out on critical information.
Damp areas and discoloration of the wood are the biggest signs that you have a leak. If any of your items are wet, that also indicates that you have a problem.
You need to trace the flow of water to find the source of the leak, particularly for puddles near walls or drips originating from the ceiling.
However, you also need to distinguish condensation from leaks. When moisture in the air contacts a cold surface, drips form, so you don’t need to have a leak to have condensation.
Checking for Damage
Aside from looking for leaks, it’s always wise to examine your shed for damage. This includes wood that is rotting or cracking or seepage through the floor.
Damaged areas will need repairs before you begin the waterproofing process. Otherwise, the wood may continue to rot, or water may keep getting in.
How to Waterproof Your Shed
Fully waterproofing your shed is a multistep process. Here’s what you need to do.
1. Choose an Appropriate Location
One of the biggest steps you can take to waterproof your shed is to select the proper location. Low-lying areas where water pools or the ground is constantly wet aren’t ideal for your shed and should be avoided.
Look for an area that gets a decent amount of sun. Sunlight helps moisture evaporate, decreasing the odds that your shed will remain wet for long after it rains.
A space that is properly graded also makes a difference. You don’t want your shed sitting over the top of a hollow or low point, essentially letting it sit where water will pool. Instead, find a level surface that is in a higher section of your yard.
The soil type also plays a role. If the soil remains damp, the chance of seepage into your shed materials increases dramatically. Ideally, select an area where the soil dries out quickly after it rains.
2. Raise the Shed Off the Ground
You can limit the impact of water on your shed by lifting it off the ground. This ensures that moisture from the soil and pooling rainwater doesn’t seep into the wood.
If you are installing a new shed, use a foundation to raise the outbuilding, ensuring it doesn’t directly contact the ground. If you already have a shed in your yard, you’ll need to retrofit it by adding a foundation underneath.
You also don’t want your shed to contact a paved surface directly. Water can collect on the pavement as well since it can’t absorb into the ground.
Not only does elevating your shed keep water from coming in below, but it also allows air to circulate underneath. This helps keep the space underneath your shed drier by preventing moisture from being trapped on the underside.
3. Choose the Right Foundation
If you want to raise your shed off the ground, you need to pick the right foundation. Ultimately, you have several options to choose from, depending on your situation.
Typically, a concrete pier or deck block foundation is the ideal choice. Not only can these be cost-effective approaches, but they aren’t overly challenging to build.
Plus, with the proper construction, they can easily last for years, if not decades.
Alternatively, you can use a concrete pad to support your shed. You want to make sure that the pad is the same size as the base of the shed.
Additionally, you’ll need to place a damp-proof membrane, or DPC, on top of the sand or gravel base before you add the concrete. This ensures that ground moisture doesn’t seep into the concrete, which can cause damage.
Concrete blocks are also an option, particularly if you want to avoid pouring a concrete base.
4. Build a Drainage System Around the Shed
Adding a gravel pad or French drain around the foundation is also wise. This gives rainwater somewhere to go, moving it away from the structure.
Effectively, you create a path for rainwater to follow, directing it away from your shed. Ideally, you want the exit to be on a downward slope. This keeps the water moving, ensuring it doesn’t pool around the structure or foundation.
5. Seal the Shed Base
The first step for sealing a shed base is to add sealant between the concrete and the frame of the shed. This limits moisture transfer and can also keep it from absorbing into the concrete itself.
You also want to seal around the base of your shed from the interior. Some shed bases have metal channels. If you seal these from the exterior, water may be trapped in these channels, promoting rust, rot and mold.
For example, if water runs down the walls, it can pool in the channels. Without proper drainage, the moisture can’t escape.
Over time, this can cause severe damage to the structure by creating an environment for the wood to rot or steel to rust.
By sealing your shed base from the inside, the water can’t as easily get into the channels. This allows joints at the corners and drainage holes to give the moisture a way to escape, essentially keeping it away from the structure.
6. Reduce Vegetation Growing Around Your Shed
Air circulation is essential when you want to promote water evaporation and prevent moisture accumulation. Vegetation can trap water against your shed, increasing the likelihood of damage.
Additionally, the root structures can damage your foundation, leading to cracks and even collapse.
Once you have the shed in place, cut back and remove any plants that contact the side. Vines like ivy can be especially damaging, so you’ll want to remove these plants entirely to prevent them from clinging to the structure. Dense bushes and shrubs can hold moisture against your shed as well, so removing these is a wise choice.
In many cases, the grass that makes up your lawn isn’t a problem. However, you need to mow it regularly to make sure it stays on the shorter side.
7. Weatherproof the Shed’s Structure
When you weatherproof a shed, you need to include the building’s floor and its walls. Since exposure to the elements is guaranteed, a 360-degree approach is a necessity.
Weatherproof the Shed Floor
When building your shed floor or selecting a prefab model, look for a frame made of treated wood. Treated wood is designed to handle the elements by sealing its surfaces and creating a stronger structure.
The floor should also be made of a treated material, like treated plywood. This lessens the likelihood that moisture will penetrate into the layers, preventing rot and mold growth.
If you need to cut any treated pieces, make sure to seal the ends with wood preservative. Most wood treatments only penetrate the surface and not the full interior of the material, so sealing the ends ensures the pieces remain weatherproof.
Weatherproof the Shed Walls
When you build the sides, you want to make sure that any OSB panels aren’t exposed to the elements. OSB isn’t designed to stave off the water.
In fact, it will usually absorb moisture quickly, affecting the glue that holds the particles together and creating conditions that promote mold growth and pieces to flake and fall off.
OSB can be great for certain interior or protected surfaces, like the inside floor of your shed or the ceiling. However, since the material isn’t water resistant, even condensation can harm OSB.
This means you need to make sure that your shed will be fully waterproof if you want to use OSB. Otherwise, it may become fall apart faster than you think.
To waterproof your walls, make sure to use tar paper or house wrap behind your siding. These products create a physical barrier that prevents water from seeping into the underlying materials. Additionally, they can reduce condensation and mold growth.
8. Install Siding
When it comes to choosing a siding for your shed, vinyl siding is a great option. The material repels water, is highly durable, maintenance free, and easy to install.
Wood siding is also an option, although you must seal it. Water-repellent sealers and paints ensure that the materials don’t absorb moisture by creating a barrier between the elements and the wood.
While the surface is durable, you will need to repaint or reseal regularly, mainly if you see cracks or other forms of damage.
Regardless of which material you choose, make sure it is installed based on the manufacturer’s instructions. Improper installation can lead to gaps between the pieces, allowing water to leak in behind the siding and cause water damage.
9. Protect the Roof
When it rains, the roof is one surface that is almost guaranteed to get wet. However, by choosing the right roof design, you can encourage the rainwater to run off the roof instead of pooling.
Gable or skillion roofs are an excellent choice as they can have a fairly strong pitch. Generally, you want the pitch to be at least 4/12; this allows the water and snow to flow down easily.
You also want to use roof felt before adding any shingles or other roofing materials. This adds another layer of protection, ensuring the plywood underneath doesn’t get wet.
Having a suitable overhang is also a must. Otherwise, as water flows off the roof, wind can blow it back onto the side of the shed. This means that more water will be running down the exterior walls, increasing the chances of damage.
If you spot any issues with your roof, you need to repair them immediately. Roof damage can allow water to flow inside your shed, into the walls, and even run down supports and soak into the floor.
Without a solid roof, you are almost certain to have problems with water in your shed, so don’t neglect your roof at any time.
10. Divert Water Away from the Shed Foundation
After your roof is in good shape, adding gutters is a must. Gutters divert rainwater away from the shed’s foundation, preventing pooling at the structure’s base.
You want the edge of the roof to encourage the water to flow into the gutter, so make sure you attach the gutters at the proper locations. The downspouts then move the water from the gutter to the ground, keeping the water off the exterior walls.
Ideally, you want the bottom end of the downspout to direct the water away from your shed and toward a safe location. This can include pointing them downhill or toward a drainage system that can divert the rainwater away.
11. Avoid Guttering Problems
Your gutters can only help you keep water out of your shed if they are used correctly. You need to regularly check them for debris, as clogs allow water to build up in the gutters and overflow back onto your roof or down your walls.
Installing leaf guards can make it easier to keep your gutters clean. If your shed is near a tree, then leaf guards are practically a must. Otherwise, you may be stuck cleaning your gutter far more frequently than you would prefer.
Extending your gutter downspouts can also be a smart decision, particularly if you get heavy rains. This moves the exit of the spout further away from your shed, decreasing the likelihood of pooling near your foundation.
12. Apply Weatherstripping Around Windows and Doors
Any doors and windows in your shed represent weak points. Without weatherproofing, water may penetrate through gaps, leading to damage.
First, you need to check your doors and windows for leaks and gaps. If you find any, apply caulk to seal the holes. Look for silicone-based caulk as the material is highly flexible and generally considered waterproof.
Second, you can add weatherstripping to your doors and windows. This ensures a strong physical barrier is present, preventing water from getting into your shed.
13. Apply Caulking
Your doors and windows aren’t the only areas that may require caulk to make your shed waterproof. For example, corner joints can allow rainwater in, so you want to fill those gaps as well.
Where each piece of siding meets the next can also be vulnerable even if the pieces fit together well. By adding caulk, you eliminate any gaps in your siding.
You also want to fill any gaps where the siding meets various other structural elements. This includes all areas where the siding meets the trim and where the roof meets the siding.
For example, around the edges of doors and trim need caulk, as well as the trim and edges of the windows. You also want to caulk the edges of air vents, cracks in the siding, and knots in the wood.
However, there are some points that you don’t want to caulk, including trim that rests on top of the siding, weep holes in windows, metal to wood joints, and siding nails.
When buying caulk, look for exterior paintable or stainable silicone versions. These are designed to handle the elements and allow you to paint the surface of the caulk, giving you the ability to blend it in with your exterior.
For straight lines, use painter’s tape as a guide and begin with a less is more mentality. Ultimately, it is always easier to add more caulk than to remove excess, so be conservative until you find the right flow rate.
If you add caulk before you paint, you can create a seamless appearance, making your shed both attractive and waterproof.
14. Insulate Your Shed
Insulation does more than just control the interior temperature of your shed; it also keeps moisture out. Begin with a breathable lining or membrane and then add your insulation.
Standard batt insulation and spray foam options can work great, but even bubble wrap can make a difference.
15. Properly Ventilate the Shed
Good air circulation is critical for moisture management. Make sure your soffits are properly ventilated and that you install ridge vents.
You can also add louvered ventilators on the sides or end panels. These promote airflow while lowering the chance that rainwater can enter your structure through the vents.
For the most impact, consider powered or solar vents. These are a more active approach, creating additional air circulation instead of relying on ambient conditions to do the job.
16. Use Waterproof Paint for Wood
All the wood on the shed needs to be protected from water. Coating trim and wood siding in waterproof paint or stain is an easy option and typically doesn’t take long to complete.
When choosing a paint, find an exterior version that is waterproof. Stick to flat, satin, or eggshell finishes, as glosses often stand out against the natural backdrop.
Usually, you’ll need to repaint every few years. To get the most life out of your paint, choose a quality brand. Otherwise, you may have to repaint sooner than you’d like.
While waterproofing a shed is a time-consuming project, it will significantly prolong the life of the structure. Your outbuilding will have suitable protection against the elements, preventing water damage that can cost hundreds if not thousands of dollars to repair.
Making your shed waterproof is a big undertaking, but it is well worth the effort. You use it to protect your belongings, so protect it too.
If you’d like to let me know what you think of this guide on how to waterproof a shed, please leave a comment below. If you enjoyed the article, feel free to share it so other people can enjoy the benefits of a waterproof shed.
Eugene has been a DIY enthusiast for most of his life and loves being creative while inspiring creativity in others. He is passionately interested in home improvement, renovation and woodworking.