How To Stop Capillary Action On Roof

How To Stop Capillary Action On Roof
  • Author: Amanda Arnold
  • Posted On: March 3, 2022
  • Updated On: August 21, 2023

A flat roof will leak if it is not fitted properly. To ensure that your low-pitch roof lasts the test of time, only work with the best. Capillary action occurs when water moves across a tight space against gravity due to the forces of cohesion and adhesion. It’s more likely to happen in hot, humid weather.

We need to look at science to figure out how it happens. In a nutshell, in a small space, water will flow against gravity on its own.

We’ll concentrate on the effects of capillary action in roofs and how to prevent it in this article. The capillary draw can happen when two metal roofing panels overlap.

When water moves up the slope between the seams of two pieces of metal, it is called a capillary draw. This problem can be solved with butyl tape or a sealant, but a faulty repair may result in more leakage. Let’s discuss capillary action on the roof in detail:

Capillary Action On Roof: An Overview

On a metal roof, seams and overlaps are unavoidable. When your roof is originally installed, it’s critical to seal these areas properly. Because of the forces of adhesion, cohesion, and surface tension, water may be pushed upward against gravity.

Capillary action is the term for this procedure. Even if the overlapping seam is above the underlying panel, it can cause a metal roof to leak at the joints. Sealing joints and overlaps with sealant or butyl tape prevents this.

It would be great to monitor these places regularly to ensure they’re still secure because roof panels can shift and migrate over time. Water will always migrate into a roof space by capillary action when allowed. In warmer, more humid situations, the process accelerates. When the weather gets colder, though, it declines.

Capillary activity in untreated steel roofs will grow as global temperatures rise and climates become humid. Moisture build-up on a steel roof will eventually lead to rust and leaks.

How Does Capillary Action On Roof Occur?

When we talk or see capillary action in detail, you can clearly see that this process is consists of three actions, including cohesion, adhesion and surface tension.

The adhesion action takes place when different particles attract each other. Secondly, cohesion occurs when molecules of the same pattern cling to each other. In the case of surface tension, dense objects can float easily on liquid.

For example, a piece of metal can easily float on liquid because of its dense structure. Similarly, surface tension occurs in metal roofing when water shrinks in small spaces such as pipes.

Use Foam Insulation To Stop Condensation Issue

Spray Foam Insulation Aids in the Prevention of Mold and Moisture Most modern homeowners insulate their homes to keep mildew, mice, moisture, and dust out, as well as to keep air from coming in and out.

Warm air condenses when it comes into touch with chilly surfaces and remains there. Secondly, drip-stop can also help prevent surface tension because of the high density of metal or any other object on metal roofing.

A drip-stop is a membrane designed to protect metal roofs from dripping or running condensation in high humidity and little ventilation buildings. Drip stop retains moisture until the temperature drops below the dew point, at which point it is released back into the air as regular humidity.

Way To Prevent Capillary Action On Steel Roofing

Even while it isn’t as widespread as it once was, it is still a concern when the right circumstances occur. When mixed wind and rain, the process takes on a new pumping dynamic. The area between the cladding overlaps allows moisture to seep in.

It settles, just like roof sheets, and starts the corrosion or rusting process. Water ingress can be prevented by applying an exterior seal to the spaces where the roof sheets overlap. Water will not be able to enter the spaces between the steel roof sheets due to this. External capillary action is no longer possible.


When dealing with a steel roof system, attentiveness is essential, just as it is with any other component of building care. Just because a new roof doesn’t imply, it isn’t prone to leaks. Investigate any dripping water within a building, particularly on the roof.

It’s simple to block water from entering by capillary action. Repairing a rusted roofing system is more difficult. Now, the choice is yours! You can deal with capillary action on roofing systems yourself or hire professionals.

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Author: Amanda Arnold

Amanda has been working with ConstructionHow since 2021. Her experience spans over 5 years in the creative niche such as home decor and trends, landscaping, renovations, and custom architectural values. As a home designer expert, she has a keen eye for the latest home improvement trends with accurate facts that readers find impossible to ignore. Being invested in home-building trends is how she has gained her lucrative expertise exploring more to bring a positive ambiance for all homeowners (and even tenants!). Currently, she lives in a beautiful beach home, a source of fascination for her.