How to Stop Condensation on Corrugated Roofing

Roof Care & Maintenance
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How to Stop Condensation on Corrugated Roofing

If you’ve noticed that the underside of your corrugated roof is coated with moisture or ‘sweating’, then you are probably having issues with condensation. Condensation occurs either when the air is cooled down to its dew point or the air just becomes so saturated with water vapour that it cannot hold anymore. This isn’t an uncommon problem on corrugated roofing but can cause some expensive damage to the roof structure as well as any equipment and livestock inside.

In this article, we will discuss some of the main causes and potential problems of condensation on your corrugated roof as well as practical ways of solving said problems.

What Causes Condensation on Corrugated Roofing?

The reason that condensation occurs is pretty simple. As warm, moist air rises and hits a cold surface, this surface then begins to cool down. As this cooling occurs, the colder surface cannot hold the excess moisture, so condensation forms.

The surface of your corrugated metal roof is far colder than the air within the building, so is a prime environment for this excess moisture build-up. You may find that this occurs especially at night time when external temperatures drop even further. 

Sometimes it can be tricky to pinpoint the exact cause of your condensation issues. Depending on the type of building you have, you may notice that a multitude of different factors are creating this excess moisture build up. These may include:

  • Livestock in agricultural buildings
  • Firewood and timber storage
  • Vehicles & lawnmowers – from melting ice/snow or from simply washing the vehicle with inadequate drying
  • Washed/wet floors
  • Storage of hay & other farming goods
  • Use of unvented heaters
  • Cooking
  • Bathing
  • Open pools of water
  • Breathing
  • Improperly fitted appliances (washing machines etc)

What Problems Does Condensation on Corrugated Roofing Cause?

Consistent levels of condensation accumulating underneath your corrugated roof can lead to an abundance of structural issues including:

  • Corrosion – When regularly exposed to moisture, your corrugated metal sheets may rust, causing the structure of the metal roof to become weaker and weaker over time.
  • Infestations – As bugs thrive in humid conditions, high levels of condensation on your roofing structure can lead to insect infestations within the building.
  • Mould/Mildew – Not only are mould and mildew unpleasant to look at but they can also have a significantly negative effect on the structural integrity of your roof. They can cause very unpleasant smells and can even cause worrying health issues.
  • Insulative Problems – Condensation can cause insulative materials to degrade, lessening performance quality and functionality.
  • Damaged to Belongings – Electronics are particularly at risk of damage when exposed to condensation. If electronic products are exposed to high levels of humidity, the moisture may damage the internal components through rusting and corrosion.

So, What is the Fix?

Although condensation can be an inconvenient problem, thankfully it can be easily turned around with the correct measures in place.

Controlling Moisture

Condensation cannot exist without the presence of moisture. Generally, completely eliminating the presence all moist air isn’t feasible, however there are ways that you can limit it within the building interior. The first way is to ensure your building has adequate drainage.

Creating a raised base will lift the building off of the surface ground and permit air flow beneath the structure. This is an effective method of limiting the path of entry for moisture to get inside. Building structures with an integral base will also help to prevent both air and moisture moving into the building from below.

Trapping water within the building creates the perfect condition for humidity to occur and condensation to form. Even something as simple as washing the floor can provide enough internal moisture to trigger condensation, so always make sure to properly vent the space and even utilise fans to aid drying.

Anti-Condensation Sheets

If you haven't choosen your roofing sheets and suspect that condensation may be an issue, you may benefit from using specially designed anti-condensation roofing sheets. These feature an integrated membrane that captures moisture before it is able to come into contact with the cold roof sheet themselves. It then releases this moisture when the air temperature increases, at which point it evaporates and the membrane is able to dry out. 

Whilst anti-condensation or dripstop roofing sheets can cost up to 40% more, it is far more convenient than fitting a membrane to the underside of your sheets yourself. Plus, many of the most popular profiles are available with an integrated membrane. This includes corrugated and box profile sheets, which are often the most susceptible to moisture build-up.

Correct Insulation

If your roof doesn’t reach too cold of a temperature, then condensation will have less of an environment in which to form. It is tricky to control the temperature on the external face of your corrugated roof, however you can limit the cold on the internal underside. Installing a high-quality insulative material is the perfect way of preventing the internal face of your corrugated roof from getting too cold and reaching the dew point.

The most common types of loft insulation for metal corrugated roofs include spray foam, rigid foam and fibreglass batts. Closed-cell polyurethane spray foam is one of the most effective insulation types as the foam will ensure that there is no contact between the cold roof surface and warm, moist air.

Regardless of the insulation type you go for; you must ensure that it is correctly installed with close bonding to the metal surface. To read up further on the different insulation types as well as methods of installation, why not check out our handy article on ‘How to Insulate a Corrugated Roof’ for more information. 


Adequate Ventilation

Ventilation is key when tackling moisture issues. Ensuring your building structure receives an adequate level of airflow will make a huge difference in the amount of condensation you see forming on your corrugated metal roof.

A simple yet practical method for this is the installation of vents along the roof ridges and under the eaves to encourage air circulation. Ridge vents are amongst one of the most popular options for metal roofs. They are fitted along the entire length of the ridgeline and are commonly utilised for both commercial and agricultural buildings.

It is important to ensure that ventilation is not overdone, as too much will draw in moisture without allowing enough to be effectively removed. Carefully calculate the right level of ventilation per square foot of the building to prevent an imbalance.

Take a look at our extensive range of roofing ventilation products here at Roofing Megastore to give you further inspiration.

Roof Pitch & Corrugations

You will typically find that the lower the pitch of your roof and the deeper the corrugations, the more issues you may have with condensation. A very low pitch roof holds condensation as it is harder for the excess water to run off.

With deeper corrugations, the water will move down from the steeper area of the corrugation but then a drip will be formed if the pitch is too low. By incorporating a higher roof pitch, you can allow the air to escape up the ridge and diffuse any humidity.


In heated buildings, use heaters that are vented to the outside. Hot unvented heaters can contribute to excess moisture by holding water which then leads to condensation.


De-humidifiers work by taking in the moist air situated in the surrounding space, then expelling once again minus the high levels of moisture. They are designed to dry out the internal building area and prevent hot, moist air from rising.

It is advised that the use of a de-humidifier is combined with other fixes such as insulation, vapour barriers and airtight seals to get the most effective results.


Condensation prevention begins right at the start of the construction process. When choosing the positioning of your building structure, try and pick an elevated space that will help to provide lots of natural drainage for excess water. If you are unable to build on a surface that is higher than the surrounding ground, you can also use a sweeping tile, a trench or gravel to help divert water away from the structure.

When working in an enclosed building structure, ensure the space is adequately vented whilst pouring any concrete. Continue this ventilation until the concrete has fully cured. It is also advised that you use caulk around the base of the building as well as any other rails to create an airtight seal.

Wood Flooring

If you have wood flooring in your building, it is a good idea to consider insulating beneath this base. Wood flooring is very porous which means that excess moisture will come up through any cracks in the floor from outside and cause condensation. You can block this with an underfloor insulation such as spray foam.

Anti-Condensation Paint

Anti-condensation paint is a great way of adding an extra layer of protection against humidity and damp. This type of paint counts as an ‘elastomeric coating’ which means it is a naturally occurring compound with elastic properties, similar to an elastic membrane.

It can be up to ten times thicker than standard house paint so can even provide some insulative properties. You should note that anti-condensation paint will only help to fix minor condensation issues and should be paired with other methods and products to prevent any major moisture build-up.

To Conclude

Although condensation can be a bother for corrugated roof structures, it is not an issue that is uncontrollable. With the correct utilisation of the methods discussed above, you can minimise moisture build-up and create a more comfortable, less humid environment in the building below.

When you do spots signs of condensation, it is always best to act fast. Fix the problem before it has the chance to cause any structural issues for your corrugated roof.

If you have any further questions or would like some further advice on the products mentioned in this post, don’t hesitate to get in touch with our friendly customer service team who will be more than happy to help. Simply give them a call on 01295 565 565 or leave a message in our handy live chat.

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