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By Amy Hanlon on 11 Sep 2023

How To Prevent Moisture In A Garage


You want to know how to keep moisture out of a garage. Maybe you already own one, and water ingress is ruining it. Or maybe you’re shopping for a garage and you’re already thinking ahead to potential problems. I admire your tenacity.

Has it been a difficult search so far?

Don’t worry – you’re in the right place now. As manufacturers of timber garages, we’re heavily invested in creating buildings that keep the water out, and we’re more than happy to share our knowledge with you to help you live your best garage life.

So let’s crack on!

Why is there water inside my garage?

Water ingress and condensation can both cause problems in a garage. 

If the contents of your garage are valuable and perishable (I’m looking at you, classic car owners) then this becomes a much bigger problem.

As well as potentially damaging the content of your garage, over time, moisture will weaken the building itself, starting a vicious circle where it becomes harder and harder to keep water out.

Remember that it’s incredibly difficult to keep any building absolutely bone dry inside. There will always be a certain level of humidity in the air. However, water becomes a problem in a building when there is an obvious build-up (like pools or a damp film) and no air circulating to dry out that build-up.

Look out for signs like rust, mould, a damp smell or puddles of water. These are all indications that moisture is causing problems in your garage.

Water ingress or condensation?

The first thing to determine is whether you have a water ingress problem or a condensation problem. Look at where moisture is gathering inside the building, and check the structure carefully to make sure there are no obvious leaks or ways for water to get in.

What is water ingress?

Water ingress very simply means that water is getting into your building. There are various different causes of water ingress. Structural problems like leaks or holes in the building will allow water in. Rising damp, poor drainage, improperly installed seals, and breathable materials are all ways that water from the outside can get in. 

Dealing with water ingress can be a royal pain in the backside, depending on the cause. Fixing it may be as simple as patching a hole, but could be as complicated as replacing the entire structure. Sometimes when water gets in the problem can’t be solved. 

Water damages buildings, whatever they’re made of. Moisture in a garage encourages mould and leaves your building and its contents vulnerable to rust, rot and damage. If a garage is going to last, it has to stay dry inside.

What is condensation?

Condensation is not the same as water ingress. Even if you live in a desert or at the top of a mountain, there is always some water vapour in the air around you. When this encounters a surface that is cooler than the air temperature, the water in the air will condense on this surface.

Condensation causes problems in a building where the air inside is warm but the outer walls are cold. If it’s bad enough, it causes the same issues as water ingress and should be avoided if you want the contents of your garage to stay dry and undamaged. 

A window showing condensation on the glass- timber garage moisture

Water ingress is about the water outside the building coming in, while condensation is about the water inside a building not being able to get out.

What causes moisture in a garage?

Water ingress and condensation can both cause problems in a garage. 

If the contents of your garage are valuable and perishable (I’m looking at you, classic car owners) then this becomes a much bigger problem. 

Is condensation common in garages?

The building material of your garage should definitely be taken into consideration. Garages are generally made of either concrete, brick or timber. Each material has different concerns if you want to keep water out.

Is condensation common in concrete garages?

If you have a concrete garage that’s in decent condition, with good solid roofing material, but you find pools of water on the floors at the base of the walls, the most likely culprit is condensation.

Because concrete conducts heat well, any warmth in your building will easily travel out through the walls. Unfortunately, any water in the air can’t penetrate the concrete, and forms condensation, which builds up on the walls and eventually pools on the floor.  

This can be particularly problematic in concrete garages that are heated.

Is condensation common in brick garages?

While brick is a better insulator than concrete, meaning that heat doesn’t escape as easily through the walls, brick garages are also prone to condensation. The best way to tackle condensation in brick or concrete garages is to insulate the building. This will eat into the space you have inside but will help stop condensation.

Is condensation common in timber garages?

An apex timber garage on a concrete base. The garage is painted dark grey and has a dark grey roller door and double-glazed windows.

Because timber is a better insulator than either brick or concrete, you would expect that condensation wouldn’t be a problem in a timber building.

But it’s a little more complicated than that. Timber garages usually have a single layer of cladding between the outside and the inside of the building. The thinner the walls, the less insulation is provided. To combat this, some manufacturers build garages with thicker timber walls.

There’s only one problem with this: timber buildings are far more susceptible to water ingress than brick or concrete buildings.

What causes water ingress in timber buildings?

Timber is a natural, porous, breathable material. It’s more than happy to soak up water and hold it in its fibres. This is great if there is moisture in a garage – the timber will easily transport it out through its breathable walls. It’s not as good as either concrete or brick for keeping outside water, well, outside!

If there’s a small amount of water in the air, timber will take this in without any problems or damage to the building. But if there’s a large amount of water (like from a honking great thunderstorm) problems easily arise.

When timber gets wet and then dries, it can change shape or warp. If your walls are made of just one layer of timber, warping can cause gaps and holes that let water into the building. This is why it’s so important to paint timber buildings

There’s a sweet spot for sheds and summerhouses – timber walls that are at least 16mm but ideally 19mm thick. After this, any additional thickness means that any warping or movement that does happen is more obvious, and causes more problems with water ingress. The extra insulation isn’t worth the potential problems with movement. 

In a changeable, mild climate like Scotland experiences, thicker timbers and log cabin-style buildings are too susceptible to movement, which leads to water ingress. 

How to prevent water ingress in a timber garage.

So, are timber garages off the list? Not at all. The solution to this problem doesn’t lie in thicker timber walls. It lies in LAYERS. Just ask Building Standards.

These rules and regulations exist to make sure that buildings in Scotland are safe and habitable. Section 3.10 of the domestic handbook states:

Every building must be designed and constructed in such a way that there will not be a threat to the building or the health of the occupants as a result of moisture from precipitation penetrating to the inner face of the building. 

The handbook goes on to list various wall designs that make this possible, like this one:

Wall type B (weatherboarding, tile or slate cladding) – framed wall of timber studs and dwangs with a breather membrane. Cladding material, on battens and counter battens as required, of timber weatherboarding, tile or slate. 

If a garage wall is constructed to these specifications, it will keep water out. If it isn’t, then it’s just a big shed, which is not the same as a garage. It won’t keep water out nearly as well.

Now, you probably don’t want to live in your garage. But if your garage has an outer layer of cladding, a cavity, and a breather membrane, you could. You’d probably want to add some extra insulation layers.

And that’s exactly what we did. This is the specification we use for our timber garages, to ensure that water ingress is not a problem. 

Can I put a wet car in my garage?

Another source of moisture in a garage can be your car. Putting wet items inside a building leads to more humidity in the air as the water on them evaporates. If the walls are colder than the humid air, condensation will happen.

If you’re the sort of person who carefully dries their precious car with a special microfibre towel as soon as you get home, you get a double gold star for car care AND moisture management. 

But if that all seems like too much work, make sure that your garage is well-ventilated when you park your wet car inside. Try leaving the main door open to ensure that the moisture from the car doesn’t evaporate into the air, where it can contribute to condensation.

If you know that your garage isn’t well-ventilated enough for this, and if you have space, park your car outside the garage until it’s had a chance to dry off.

Dehumidifiers and fans can also help, or consider looking at more long-term options for ventilation.

How do I get rid of moisture in a garage?

If you already have a garage, and you’re having problems with water ingress or condensation, here are our top tips:

  1. Survey the garage for any leaks or holes and fix these if possible.
  2. Insulate your garage to prevent condensation.
  3. Air the building regularly by opening all the doors and windows for a couple of hours.
  4. Don’t put wet items inside your garage.
  5. Make sure there’s adequate ventilation.
  6. Use a dehumidifier or moisture traps inside the garage.

Looking for a timber garage?

If you’d like to see a timber garage in the flesh (or the timber, I guess…) come on down to our Show Area here in Errol. Our Sales Team are happy to answer any questions you might have, and they’ll be very impressed that you know the difference between water ingress and condensation!

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