Summer house in the sun

Damp Proofing Your Summer House

5 August 2022

A summer house is a great thing to have in the back garden, and over the summer many people enjoy sitting out in their summer house, taking in the sun whilst enjoying the outdoors.

Once summer is over though the question remains of how to keep your summer house in top condition all through the wet and cold months, so that it remains damp and mould free for when you need it again.

So, with all that in mind, how can you stop damp in a summer house?

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For help with damp proofing, call 0800 288 8660 or

Why is Your Summer House Damp?

Dry rot fruiting body

There are two main reasons that a summer house might be damp, and both can be avoided if you act prudently and make sure to be thorough.

The first reason that your summer house might be damp is because of water ingress. Water ingress is the simple act of water making its way into the wood (or whatever material makes up the summer house), which causes damp.

This can happen via a fault in the summer house itself – a crack in the wood, a leak in the roof, or it could happen (similar to penetrating damp) through a process known as capillary action. Capillary action is when moisture within the ground is drawn up into your summer houses materials, in a similar process to what is known as rising damp.

The other reason that your summer house might develop damp or dry rot is because of condensation. Condensation occurs when warm air within a structure (or any environment) comes into contact with a cool surface. The warm air will contain moisture in a gaseous state, which (once in contact with a cold surface), will revert back to its liquid state.

That’s why you commonly find condensation on windows – the cold air outside your home is in direct contact with your windows, and once the warm air inside touches it, you develop condensation.

If this is allowed to happen over a long period of time, then you could see a steady and regularly growing case of damp, which might lead to black mould, dry rot in your timber, and more if not treated.

Request a survey

For help with damp proofing, call 0800 288 8660 or

Ways To Protect Your Summer House

A summer house is worth a lot more than the sum of its parts, and that means that it’s worth the cost of routine checks, maintenance, and upkeep to make sure it stays in a nice, pleasant, usable state.

Read on for some of the most vital steps you should take to keep your summer house free from damp and dry rot.


If you weren’t aware, condensation is one of the leading causes of damp in any structure. Warmer air comes into contact with cooler surfaces, and the moisture contained within the warm air condenses on those cool surfaces. If that happens enough, you end up with damp.

Now, you might think that a summer house isn’t going to be generating a lot of heat, or that there won’t be that much warm air inside a summer house since they aren’t heated.

However, a summer house (by its very design) is meant to trap heat and keep itself and its inhabitants warm long into the evening – a little like a greenhouse. That means that even if you aren’t sat inside a summer house, its going to be trapping warm air within – and if it’s left unventilated that warm air can very easily turn into condensation.

So, to avoid a build up of condensation and the onset of damp, black mould, and other issues in our summer house consider installing some ventilation options within the summer house’s structure. Something simple, like vents within the wood or a trickle vent in the windows of the summer house can go a long way in helping the warm air ventilate safely.

The simplest option when it comes to ventilating your summer house though is opening its doors, and allowing fresh air to flush out the warm, moist air. This is obviously a lot easier in the summer, especially when its not raining and you are able to comfortably sit in, or get out to your summer house.

In winter though, you are going to need built in ventilation options just to let any trapped heat escape. Think about the addition of vents, breathable materials, or even just airing out your summer house on warmer days.

Wood Treatment

One of the main reasons that your summer house might develop a damp problem is because the timber itself isn’t treated or protected from the elements. This means that even a slight rainfall, or a morning mist could be enough to penetrate your summer house’s timber and start the spread of damp.

Damp isn’t where this would stop either. You would likely see the beginning of dry rot in your timber too, which if left to grow unchecked can easily spread its distinctive orange fungus to other timber in your summer house, ruining all of the unaffected timber with the gradual and steady spread of dry rot.

To stop this from happening all you would have to do is make sure that the timber in your summer house is correctly treated. Make sure that you take the time to properly coat your summer house in a waterproof seal – and that you reapply as often as required.

It’s not a major project, and most people will have already sealed their summer house during the construction process at least once. Make sure that you keep your eye on the timber itself though, as any signs of water ingress means that you are either going to have to repair a hole in the summer house, or break out a paintbrush and reapply the seal.


Your summer house is a place to enjoy the sun, so why would it need to be fitted with insulation?

Well, first off think about how the temperature drops in an evening. Chances are, if you are enjoying your summer house in the day you are going to have your summer house doors open – and it will be warm enough that the temperature both inside the summer house and outside will be one and the same.

However, as the evenings draw in you might start to close the summer house doors whilst enjoying a light and cool evening with the doors closed. If that happens then the inside of the summer house is likely to become warmer than the outside – and now you are facing the problem of condensation.

Insulation however helps you maintain the temperature within your summer house, and combined with adequate ventilation you can minimise the risk of condensation occurring. A thin layer of insulation on your summer houses walls or ceiling can go a long way in reducing the risk of condensation building up and leading to damp on the inside of your summer house.


By repairs, we don’t mean major overhauls and replacing entire walls. Instead, check over your summer house periodically to make sure that it hasn’t developed any holes, leaks or other ways that water might make its way in.

Simple actions like patching potential leaks in your summer houses ceiling, making sure that windows close fully, and the timber is up to scratch go a long way in increasing the longevity of your summer house – especially when its safeguarding against the likes of damp and dry rot.

Make sure to look over your summer house after heavy rain, snow, or storms, just to make sure that no drastic or immediate repairs need to take place. Damp and dry rot are problems that can occur through the smallest cracks, so you don’t need to be missing the roof on your summer house for the timber to be compromised.

We might not be able to help with smaller outbuildings, but if you have a larger sized shed, summer house or other outdoor structure currently suffering from damp or dry rot our team might be able to help.

Give us a call and see if we could potentially help you with your outbuildings property care issues on 0800 288 8660, or fill in a contact form and our team will be in touch.