Effect Of Freeze-Thaw On A Roof

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A roof with snow on it that is suffering from freeze-thaw weathering

We take a look at impact of freeze-thaw on a roof, the weathering that can occur, and the solutions against cold weather on a roof.

While snow isn’t a common occurrence in the whole of England, sub-zero temperatures very much are, so given the amount of rainfall commonly seen in winter months, the combination of rain and sub-zero temperatures can lead to a process known as freeze-thaw weathering.

What Is Freeze-Thaw Weathering?

Moisture is constantly present in our air, whether it rains or not, and that moisture will inevitably seep into the nooks and crannies of roof coverings.

As temperatures drop below zero this moisture will freeze and in doing so expands, before thawing and contracting as the temperature rises.

This cycle repeats over time, putting significant stress on the roof, leading to damage.

How Can Freeze-Thaw Weathering Damage A Roof?

This repeated cycle creates pressure that when pushing on things such a roofing tiles or roofing felt where there is no give, causes cracks to form and expand..

On top of this, some roofing materials will naturally contract in freezing temperatures, exacerbating the problem further.

The freeze-thaw cycle can cause a variety of issues for your roof, some of the more common are:

Exacerbating spacing between roof coverings: Roofing materials should be evenly spaced. The repeated expansions and contractions push the roof coverings apart creating more or larger gaps for water to penetrate.

Dislodging Flashings: Metal flashings on a roof create a watertight seal. The freeze-thaw cycle can warp these flashings, breaking this seal, creating entry points for moisture to enter the building.

Penetrations to Roof coverings: A small defect on a roof can be drastically exaggerated by the freeze-thaw process. What may have been an inconspicuous crack, can soon significantly increase in size and lead to failure of the waterproofing.

Additional strain to detailing: The most vulnerable points of a roof will always be the details, these naturally carry more strain as the roof expands and contracts. Any small defects, caused by natural ageing can be further exaggerated

Ice Dams: Another type of damage associated with freeze-thaw are ice dams, which you can read more about here.

Long-Term Effects Of The Freeze-Thaw Cycle

There are several ways in which the freeze-thaw cycle can damage your building in the long term.

The damage on a roof can be subtle at first, but significant as the problem persist.

Repeated cycles can lead to larger areas that have failed, and therefore letting water into the building.

The freeze-thaw cycle accelerates the wear and tear of a roof. Which, if left unchecked, can lead to the roofing system failing prematurely.

By addressing these issues early or at the design stage, it is possible to avoid this damage almost entirely.

How To Protect Your Roof From The Freeze-Thaw Cycle

The best thing to protect your roof is to keep your building well ventilated, allowing airflow which will keep the roofs temperature even and prevent ice forming.

Scheduling regular roofing inspections and maintenance to ensure any small defects are addressed, and don’t allow the impacts of freeze-thaw to exaggerate these. Neglecting your roof regardless of the season is not a strategy that pays off.

For more information read our articles about ongoing maintenance.



In Conclusion…

Hopefully this gives you an idea of the impacts the Freeze-thaw cycle can have on roof covering, and an idea of what to look for: A few additional points of consideration to take away are:

  1. No particular type of roof system is more susceptible to freeze-thaw than another. Though older roofs are more vulnerable, it can also occur on newer roofs.
  2. Freeze-thaw damage may not be covered by your warranty, so make sure to refer to the specific terms and conditions.
  3. Freeze-thaw can have a dramatic impact on a pre-existing leak as when the moisture unfreezes it causes a large amount of water to push through the leak all at once.


Here at Maguire Brothers we’ve been dealing with freeze-thaw at both the design and installation stage across all nature of roofing and refurbishment projects.

So if you require any further information, do not hesitate to get in touch with one of the team here.

This article, as with all other articles we produce, is for guidance purposes only. It does not constitute formal advice and should not be relied upon as such. For bespoke, unbiased advice relating to your commercial roofing project please contact us and we would be pleased to assist.

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