shed metal corrugated roof

How to weatherproof a shed and extend its life

Most off-the-shelf sheds will provide a reasonable amount of weatherproofing properties and will provide protection from the elements. After all, this is the purpose of a shed. You want a secure structure to keep your expensive things safe and dry. Even if you are considering building your own shed, several techniques can be applied before and after construction to enhance the protection and prolong the life of your shed. Read on to find out the best way to weatherproof a shed.

shed with gutters and corrugated roof

Introduction

The importance of weatherproofing a shed

Weatherproofing your shed will help you protect your important items, tools, gardening equipment, bicycles, toys and whatever else you might keep in your garden. The biggest killer of wooden sheds is rot. Rising rot from the ground and water penetration from the roof and walls. When we buy a flat-pack shed, from anywhere, the manufacturing process is normally rushed and materials can be of poor quality.

Wooden panels can have knots, splits and small gaps that can allow the ingress of rainwater. This is pretty normal, even when buying a shed from a premium-quality supplier. Even a good coat of paint can leave gaps for water to get in. Over time, the inner walls and floor can rot and perish so we need to take time to address this during construction.

badly weathered shed
Badly weathered shed

Some of you may also use your sheds as a hobby space in which you keep all your bits and pieces. Whether it’s for woodworking, model building, photography or an art studio you will want to ensure everything is safe and dry. Therefore you might also wish to add some insulation and heating to keep warm in the winter. I’ll touch on this further on in this article.

What causes wood to rot?

Wood rot is caused by the growth of certain types of fungi, which break down the cellulose and lignin in wood. The fungi thrive in moist environments and typically require a moisture content of at least 20% to grow.

rotten wooden shed

There are several factors that can contribute to wood rot, including:

  1. Excessive moisture: Wood rot is most commonly caused by excess moisture in the environment. This can be due to poor drainage, high humidity, or water leaks.
  2. Poor ventilation: Insufficient airflow can trap moisture around the wood, promoting the growth of fungi.
  3. Lack of maintenance: Neglecting to maintain and repair the structure can also lead to wood rot, as damaged or weakened wood is more susceptible to rot.
  4. Organic debris: Organic debris such as leaves and branches can accumulate around the structure providing a perfect place for fungi to grow.
  5. Insects: Wood-boring insects such as termites and carpenter ants can weaken wood by tunnelling through it, making it more susceptible to rot.
  6. Exposure to weather: Exposure to sun, wind and rain can cause the wood to degrade and rot over time.

It’s important to address any issues of wood rot promptly in order to prevent further damage and to ensure the safety of the structure. Regularly inspecting and maintaining the wood elements of the structure, keeping organic debris away, ensuring proper ventilation, and addressing any leaks or other sources of moisture can go a long way in preventing wood rot.

Steps involved in weatherproofing a shed

Whether you already have a shed or are planning to build one there are a number of things you can do to protect and prolong its life. You can add extra layers, change doors and windows, improve the base, add heating, paint it and much more to give you a structure that will last for many years.

The main things we need to focus on are as follows:

  • The shed base. This needs to be strong, level and should prevent moisture from rising into the main structure.
  • The shed floor. Many flat-pack sheds will have a basic flooring that can be strengthened, waterproofed and insulated.
  • The shed walls. These can be treated with wood stain or paint and can again be insulated.
  • The windows and doors. Basic perspex windows can be upgraded and doors can be strengthen or replaced.
  • The shed roof. Basic shed roof felt can be upgraded and additional layers can be added to improve longevity.
  • Improve drainage on the ground and around the roof.
  • Remove, repair or cover any gaps within the structure.

Let’s take a look at these in more detail and I’ll show you some interesting techniques to implement whether your shed is already built or you are planning to build a new one.

Weatherproofing a new flat pack shed

When building a new shed, you’re in the perfect situation to weatherproof a shed because you’ll have easy access to each section of the structure. Certain parts of this process are far trickier when trying to weatherproof an existing shed, but not impossible. Within this section, I’ll show you how to weatherproof a new shed. I’ll then follow up with existing buildings.

Before you start – Think about the shed base

The base of your shed is vitally important as it provides the foundation. It needs to be strong, level and will need to prevent water from sitting stagnant near your shed floor. Solid, flat shed bases need to ensure water runs off so that the shed bearers are not sat in water for long periods of time.

A solid flat shed base made from a concrete slab or a patio-style base should have sufficient run-off when built. For further protection, you may wish to build your shed floor/bearers on a raised plastic base. These will raise your shed floor off the ground and away from stagnant water. The same plastic bases can be used for level ground without a solid base but you will need to be careful the shed isn’t located in a low-lying area of the garden. Heavy rainfall may still be able to reach your shed bearers.

In most cases, you will not be provided with a base when buying a flat-pack shed. A base will need to be constructed before you start. Most flat-pack sheds will be provided with a simple bearer strip wood system. These can be suitable to place onto a solid base but will not stand the test of time, especially if your base has insufficient drainage.

When constructing my shed bases I prefer to go with a raised plinth approach. This will provide a solid foundation for the shed and will prevent it from sitting anywhere near water. It can be easily hidden and will ensure your shed lasts for 3 or 4 times longer than it would normally. The same structural method can be built when building a shed base on uneven ground.

raised plinth shed base

You can also consider building your own raised wooden platform which can be integrated with some decking for a feature building. In the below image I have constructed a wooden frame on which my garden building is constructed. This method helps raise the wooden structure way off the ground and provides a strong, level platform.

wooden frame base
kent office price drop

Weatherproofing the shed floor

This is an easy one. If you are building a flat-pack shed you will most likely have an 18mm (or 11mm) chipboard base onto which you will secure some strip wood bearers. To prevent moisture from reaching the chipboard floor you can add a thin plastic sheet. Simply place the plastic sheet between the chipboard and the bearers before screwing them together.

shed construction

You can buy the damp proof membrane at B&Q here.

It’s a small cost for a lot of benefits so consider doing this when building your shed.

Protecting the shed walls from deteriorating

Wooden shed walls are generally made from thin 11mm spruce cladding with a basic 20x20mm timber frame. Most flat-pack sheds will be constructed from cheap materials which can have small holes from knots and splits in the wood. We can weatherproof the shed walls by filling these holes and making them watertight. I did this with my last shed with some silicone sealant. Simply squirt some into the holes (from the inside) and smooth them over with your finger.

Exterior wood filled can be used on the outside of the shed to further cover any holes and smooth over any cracks or uneven splintering in the wood. Ensuring your shed is watertight is essential for weatherproofing. Once you have completed this task and the sealant/filler has dried you can move on to protecting the wood.

Preserving the wooden walls of your shed

The best way to waterproof a shed’s walls is by painting or staining them. We applied a wood stain to ours, followed by a couple of layers of paint. A decent outdoor timber stain and paint should be used for this purpose. A good outdoor wood stain will penetrate the grain and soak into the wood. The paint will provide an impermeable layer around your garden building which will prevent mould and rot to start building up in the wood. Ensure you apply at least two coats to a new shed and repeat annually.

It’s important to regularly check the building for new holes and damage and repair them as soon as possible. We used to have a shed where the neighbour’s tree grew too close. During strong winds, the tree branch would rub against the roof felt which slowly wore through. Water was then able to penetrate the wood and over time it began to rot. It was difficult for us to see this as the visibility and access to this side of the shed were obstructed. Be sure to build your shed away from trees and branches and regularly check to ensure nothing is growing too close.

Ventilation

Ventilation can help air circulate around your shed and help prevent the build-up of moisture in the air. After all, moisture is one of our shed’s biggest weaknesses. Most sheds can benefit from having a small ventilation panel installed on the walls. These can be cheap and easy to install, even after construction. If you notice a build-up of moisture within your building then it’s worth installing a vent on the wall, normally high up on one side.

Insulating your shed

I have a separate article that goes into detail about this topic so it would be easier for you to read this if you are interested in turning your shed into a habitable space. Shed insulation comes in many different shapes and sizes and can be a complex task. Click the button below to open this article in a new tab.

garden room insulation

Weatherproofing your shed roof

The shed roof is the most important part of your shed to protect against the elements. A basic roof will consist of a large piece of sheet materials, most likely a chipboard or a tongue and groove spruce covered with a felt watertight barrier.

It’s important to ensure the felt is installed correctly on your roof. Here’s a great video to show you how it’s done.

Some sheds will be supplied with a thin, cheap felt which splits and cracks easily. It is worth upgrading this to a thicker, more durable felt like this one: Roof Pro Super Green Shed felt, (L)10m (W)1m

split shed felt
Split cheap shed felt

Adding additional layers can improve the water-resistance of a shed. Adding a layer of EPDM rubber roofing or sealing your felt with a roof felt adhesive is worth adding. An adhesive can help secure your shed felt to the wooden roof boards and prevent moisture from penetrating the roof. It seals small holes and gaps which can be ideal if you missed any during the build process.

EPDM rubber sheeting can be added in place of your felt roofing for a stronger, more durable finish. EPDM rubber sheets can be supplied in very large sizes so you can cover the whole roof with one piece. They are normally glued down on top of the roofing boards.

Another great way to further weatherproof your shed roof is to upgrade the roofing. There are a few different options available. Add these on top or replace your existing roof. Here are a few of my favourites:

shed metal corrugated roof
Shed with metal corrugated roof upgrade
Corrugated Bitumen roofing

This kind of roofing can be added on top of an existing roof or in its place. It adds a tougher, stronger and more durable roof to protect against heavy rain and strong winds.

Corrugated metal galvanised roofing sheets

These sheets are similar to the bitumen sheets but add an even stronger and more durable finish to your roof. They’re easy to install, affordable and will last a lifetime.

Synthetic slate tiles

These synthetic tiles are perfect if you want a strong roof that really looks the part. Turn your shed into a head turner and improve the durability and weatherproofing properties with these sleek-looking tiles.

Lightweight plastic roofing tiles

If you like the tiling look then these tiles are another great option. Easy to install, durable and a great weatherproofing upgrade for your shed, summer house or garden office.

Facia strips

Your shed will likely come with facia strips that surround the roof. These are normally the first thing to deteriorate and rot on a shed as they tend to allow water to sit on them. They’re not particularly a functional part of a shed and merely provide a way of hiding the unsightly finishing of the felt. They are an aesthetic finish.

Before installing your facia boards it’s a good idea to thoroughly paint or stain them, front and back. Apply two or three coats of your chosen wood preserver. This way you will give the facia boards every chance to survive for long periods of time in all kinds of weather conditions.

Some people also upgrade their facia boards with plastic or metal which are far more durable than wood.

Improving drainage around your shed

As mentioned above, your shed should be raised off the ground to prevent water damage to the base and floor. Creating suitable drainage around your shed is also key to preventing water damage from below. Ensure you have good drainage channels around your shed or build your shed on a slope, hill or raised section of your garden. I’ve written a detailed guide on this should you wish to build your shed on uneven ground. Follow the button below to read the post.

You should also strongly consider installing gutters so that water falling from the roof can be directed away from the walls and base. I’ve noticed on some of my older sheds that the walls which are more exposed to the weather tend to deteriorate quicker than others. By adding gutters to the eaves you can prevent additional water from dripping onto and soaking into the wooden walls. For the cost of about £120, you can install a complete gutter system and help divert the water away from your expensive shed.

shed gutters

Gutters also prevent water from dripping off the roof and splashing back onto your shed near the ground.

Here are a few others ways to help with drainage around your shed.

  • Grade the ground: Make sure that the ground around your shed slopes away from the foundation. This will allow water to flow away from the shed, reducing the risk of water damage.
  • Install a French drain: A French drain is an underground drainage system that can be used to redirect water away from the shed. It is made up of a trench filled with gravel and a perforated pipe.
  • Use mulch or gravel: Adding a layer of mulch or gravel around your shed can help to improve drainage by allowing water to flow more easily through the soil.
  • Keep the area around the shed clear: Make sure to keep the area around the shed free of debris, such as leaves and branches, to ensure that water can flow away from the shed easily.

This concludes the section about weatherproofing your shed when building from fresh. Now let’s take a look at some more ideas when we want to weatherproof an existing shed.

Weatherproofing an existing shed

If you’re working with an existing shed then you need to thoroughly check over the interior and exterior of the shed to check for signs of moisture and water damage. Signs of mould and rot will indicate there is a problem somewhere that needs to be addressed. Sometimes these issues will be obvious, such as a hole in the roof, whilst other times it might not be so obvious.

old weathered shed

Giving the shed a good clean inside and out should be your first step. That way you’re going to find any areas that need repair or adjustment. In some bad cases, you might need to replace some of the cladding or structural timber. This isn’t really a difficult job but you will need to try and find matching cladding.

If your floor is damaged you might be in a tricky situation where the whole structure needs to come down whilst you replace the floor. If this is the case then you can ensure the new base has some kind of waterproof barrier underneath. As you would in a new build.

Replacing or upgrading existing windows is another job worth considering, especially if your windows are broken or cracked. Installing weatherstripping around windows and doors is an easy task and will add extra protection from the elements.

Once you’ve cleaned and repaired any rotten wood you can then move on to weatherproofing. You can follow most of the above guides to weatherproof a shed. To recap I will list them again here:

  • Ensure your shed has a raised base and add a layer of waterproofing if possible.
  • Paint or stain the exterior walls. Try and apply at least two layers, but ideally 3 or 4.
  • Ensure your shed felt is installed correctly and upgrade the roofing if your budget allows.
  • Improve drainage with ground water channels and install guttering.

Conclusion

In conclusion, weatherproofing your shed is an important step to ensure the longevity and stability of the structure. By following the tips mentioned in this article such as installing proper roofing, adding weatherstripping, waterproofing the walls and floor, and maintaining the structure regularly, you can effectively protect your shed from the elements. Remember, a waterproof shed makes for a long-lasting building.

Additionally, ensuring proper ventilation, proper drainage, and keeping the area around the shed clear of debris can help to prevent wood rot. Remember that regular maintenance and inspection are crucial to maintaining the longevity of your shed and to catch any issues early on. By taking the necessary steps to weatherproof your shed, you can ensure that your structure will be a durable and reliable storage space for years to come.

Whether you’re building your own shed or constructing a flat-pack shed there are many ways to weatherproof it and increase its lifespan.

DIY shed plans

If you’d like to have a go at building your own shed then check out my shed plan guides. These step-by-step guides take you through every part of the build process with detailed drawings, cut lists and a full materials list. Simply print the materials list and give it to your local builder’s yard for everything you require.

More garden building guides

Check out my free garden-building guides for some inspiration and further guidance.

Thanks for reading. Please feel free to leave a comment below.

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