Thermal Shock

Roofs are responsive by design. They react to temperature changes. Days are warmer than nights, so the roofs expand when it is warm and contract when it is cold. Generally the relative movement from the daily high to the daily low is minor, and takes a significant amount of time for the roof to lose elasticity or, in the case of metal roofs, for the seal to deteriorate.

Let’s take our company headquarters as an example. We are located in Kingsport, TN. In January the average daily high is 46 degrees and the low is 26 degrees. This is a difference of about 20 degrees a day on average and  gradual expansion and contraction. Over the course of several days, the temperature range still averages around 20 degrees between the high and low.  So, what happens when we have extreme temperature changes, like on January 6, 2014? The low was 2 degrees and the high was 51 degrees.  From January 7, 2014 to January 9, 2014 the temperature went from a recorded -1 (My car said -8) to a high of 52. This is an enormous change for a roof in two days.  These extreme temperatures cause a roof to expand and contract at a much higher rate than normal, accelerating the reduction in elasticity and deterioration of seals.

The following content was originally shared with subscribers to our electronic newsletter, however, given the recent rapid temperature changes in the Southeast, this is relevant now.

My Metal Roof Moves?

Yes, metal roofs move. This is part of the design and natural properties of the metal panels. Metal naturally expands and contracts in response to temperature changes. When the temperature is warm, the roof expands. When it is cold outside, the metal contracts. This is often referred to as thermal expansion. Roofing contractors take this into consideration when installing metal roofing, but it is not problem free.

Over time, the relative movement from thermal expansion can cause the panel seams and flashing to separate and the fasteners to back out. A normal response is to repair these areas with a sealant or coating. Yes, this works for a while. The metal will continue the thermal expansion, and soon the problems will begin again, this time taking the coating and/or sealant with it.  Is this a sign of poor installation? Sometimes, but more often than not, this indicates a metal roofing system may not be the solution for your roofing problems.

With the relative movement from the thermal expansion comes a higher risk of leaks. Even slight openings in the panels, fasteners, flashings, or sealants can provide opportunities for moisture to enter the roofing system. On flat roofs, water can travel. This means the leak inside may be 20 feet away from the point the water entered the roof through a small opening.

Allow LaFerney Commercial Roofing to provide a free evaluation of your roof. Our consultants can identify potential problems with all types of roofing systems. LaFerney Commercial Roofing offers a retro-fit option. This system installs directly over your existing metal roof for durable protection. To learn more about this option, click here, or call 800-633-3119.

Separation of rusted metal panels as a result of thermal expansion.

Separation of rusted metal panels as a result of thermal expansion.

 

The fastener has worked itself loose due to thermal expansion.

The fastener has worked itself loose due to thermal expansion.

Thermal expansion has caused the seal between the metal panel and the skylight to fail.

Thermal expansion has caused the seal between the metal panel and the skylight to fail.

 

The coating is cracking at a seam due to relative movement.

The coating is cracking at a seam due to relative movement.

 

This large gap at a seam is a result of thermal expansion.

This large gap at a seam is a result of thermal expansion.

 

A fastener is working loose through a sealant.

A fastener is working loose through a sealant.

Another view of a fastener working loose through a sealant.

Another view of a fastener working loose through a sealant.

 

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