A few basic steps can stop damp, mould, and damage from building up in sheds. Here are some ways to waterproof your shed and keep everything inside safe and dry year-round.
How to Waterproof a Shed
Raise your wooden shed off the ground
If your shed is sitting straight on the ground, it’ll soak up moisture and invite damp and pests. The best thing is to raise it slightly. You can use a wooden base, floor bearers, or build a concrete shed base if the building is big and heavy.
Make sure there’s airflow underneath, as this will keep the timber dry and protect it from potential rot. You’ll also want to avoid placing it directly on paving, as water can pool there.
Tip: Before lifting, empty your shed so it’s lighter and easier to move. Get a mate to help, and use a crowbar to lift each side.
Gutter maintenance for a waterproof shed
Blocked gutters cause water to spill over and soak the shed. Clear out leaves, mud, and anything else clogging them up. No gutters? Worth fitting some, as they help stop water damage and let you collect rainwater for the garden.
Check windows and doors
Look for gaps or cracks around the frames; timber shrinks over time and lets water in. Fill any gaps with a shed window sealant or expanding foam. For doors, use draught excluder tape. If you spot rot, dig it out, fill it with wood filler, then sand and repaint.
Inspect and repair the roof
The roof takes the most damage, so check it often. Look for tears or worn felt, especially along the edges and ridge. Patch small rips with roof sealant and felt. If the felt is too far gone, replace it with new felt roof tiles, EPDM rubber, or a waterproof shed membrane.
Treat your wooden shed
Before applying the preservative, ensure there’s enough space around for good airflow. This helps keep it dry. Use a water-based stain or paint—it dries quickly and reduces moisture. These preservatives are also low in toxins, making them safer.
Tip: Apply the shed treatment evenly to protect the wood from rot and damage. Repeat the treatment every two years to maintain a waterproof garden storage solution.
Insulate and ventilate
Shed ventilation and insulation go hand in hand when it comes to keeping damp out of your shed. Good airflow stops moisture from building up. In contrast, insulation keeps the temperature steady so condensation doesn’t form inside.
The easiest option is to install vents on opposite walls to allow air to circulate. Cover them with bug-proof mesh so you don’t invite pests in. If vents aren’t possible, open a window or leave the door ajar.
For insulation, expanded polystyrene (EPS) boards or foil-backed bubble wrap do the job. PIR insulation boards give better thermal resistance, though they cost more.
Why Weatherproof a Shed
Weatherproofing goes a step further than waterproofing. It protects your shed against everything the seasons throw at it, be it rain, frost, or wind. This guide can also be applied to wooden sheds – feel free to check it out for the steps.
As per RHS, timber kept in contact with moisture will decay, even if treated. That decay occurs more rapidly when cold, damp air is allowed in. Once the wood weakens, the whole structure is at risk.
Take care of weatherproofing, and your shed will stay safe without extra costs.
Damp-Proofing the Base
Even raised sheds can get damp from the ground. Put down a damp-proof membrane between the floor and the base. It’s a sheet of strong plastic that stops moisture from creeping up into the timber. The same method is used in house building and works for sheds.
If you’re putting in a new base, lay the membrane before the floor bearers. For an existing shed, it’s a bit trickier, but if you spot damp patches inside, it saves a lot of hassle later.
Learn more here: A Guide on How to Damp Proof a Shed
Drainage Around the Shed
Water pooling around the base is one of the main causes of leaks and damp floors. If the soil doesn’t drain well, you can install a basic drainage trench. Dig a shallow channel along the sides of the shed and fill it with gravel. This lets rainwater flow away instead of sitting against the timber.
On heavy clay soil, fitting a land drain pipe can help even more. It takes some work, but this ensures your shed stays dry all year.
Roof Repairs and Replacements
Felt roofs in particular don’t last forever—they crack, lift, or tear with strong winds. If you notice leaks even after patching, it’s better to replace the whole covering. Options include new felt, felt shingles, or a longer-lasting EPDM rubber sheet. EPDM lasts 20 years or more with very little care. It costs more at first, but it will save you hassle in the long run.
If your shed has old or broken roof tiles, replace them before they shift further or let in water. Always check the ridge and edges, as these are the first spots where damage shows.
This guide should help you out: How to Re-Felt a Shed Roof
Round-up
To waterproof a shed may take a bit of time, but it pays off. Once it’s done, along with the other approaches above, your shed will stay protected all seasons.
Hopefully, this guide gives you the nudge to set aside some time to care for your garden building!
Up next on your reading list: The Must-Have Tools in Your Shed for Repair and Maintenance
