The Gutter Expansion Problem

Unequal gutter expansion effects many seamless aluminum gutter installations every Spring and Summer. The problem we are discussing becomes evident as a bowing out of the face of the gutter...sometimes to the extent that the face of the gutter tears vertically at the front face.

As you may be aware that aluminum expands and contracts but not as bad as vinyl products. Please keep in mind during installation of gutters during temperatures below 30 degrees that the aluminum is contracted fully and that there could be a problem with buckling during the 100 degree summers. It has been the experience of the aluminum industry that these gutter expansion problems usually occur during the 2nd year after installation.

Below are some tips offered by the gutter industry.

A 50’ piece of gutter installed at 35 degrees F, if allowed to, will expand nearly ¾” over a year’s time. Anecdotal evidence suggests that this is not a problem which is either color or length dependent. The study has seen a 40' piece of sandstone tear in three places, while an 85’ piece of Sherwood looks fine.

The study suggests the following to help prevent gutter expansion: Gutter machine's must be adjusted, and constantly checked to be sure they remain in adjustment.


The two places that gutter machines have the most pressure on them while forming coil are at the top and bottom front edge of the gutter. It stands to reason that when machines go out of adjustment, these two places are normally the first and worst areas.

Gutter expansion problems are more evident over sidewalks and driveway, as they reflect more sunlight. The gutter was installed when it was “cold”, below 35° F, but the problem was not noticed until months later, when it began to warm up. The top front edge of the gutter is curving away from the building. This requires the installer to pull the gutter to the building with the hidden hanger, putting stress on the face of the gutter. The bottom of the gutter at the bottom front edge is running “downhill”, Almost always, the gutter is installed with hidden hangers.  

Be extra aware of installations over concrete or asphalt. You may want to run the guttering out and place it upside down on concrete or asphalt in the hot sun during cold weather installation to make the gutter expand a little before it is installed. You may want to use spikes and ferrules over these areas.

Don’t work when it’s cold? Just kidding! But understand the material’s limitations and propensities.

Put a zip screw through the top of the gutter which will go into the hidden hanger at the hook, which should prevent the front from moving. This will help prevent the front from growing while the back stays tight to the building.

What is an expansion joint?

Expansion joints are sheet metal features that bridge two sections of gutter while allowing them to move independently. To limit the effects of thermal gutter expansion due to temperature change, 50 ft. is the practical maximum length before an expansion joint is required on seamless aluminum gutters.


It is essential to provide expansion joints in all gutter installations to allow for movement due to temperature changes. In planning gutter expansion joint locations, it should be recognized that an expansion joint acts as a dam in the gutter, therefore, the number and placement of downspouts will be influenced.

Simply stated, the gutter is terminated with an end cap as if the gutter has ended. Then, a space of an inch or two separates that section of gutter from the next, which begins with another end cap. The space between the pair of end caps is covered with an expansion cap to prevent water entry and to allow the separate sections of gutter to move back and forth with temperature changes. A cover plate is then placed over the expansion joint to improve the appearance of the gutter.

Installation of the cover plate should not restrict the movement of gutter sections. Because an expansion joint consists of two terminations in the gutter system, it creates a dam in the system, preventing the flow of water across the joint. Therefore, it should be located at a high point in the gutter, as water will then flow away from the expansion joint rather than try to flow through it. When a high point is not available, a drain outlet must be included or added to the gutter system on the uphill side of the expansion joint.

THIS INFORMATION IS ADAPTED FROM THE ARCHITECTURAL SHEET METAL MANUAL, FIFTH EDITION, FROM THE SHEET METAL AND AIR CONDITIONING CONTRACTORS NATIONAL ASSOCIATION, INC. (SMACNA)

TEMP. F

10’ PIECE

50’ PIECE

120

3/32”

5/16”

100

3/32”

7/16”

75

1/8”

9/16”

35

5/32”

11/16”

AS CAN BE SEEN FROM THE ABOVE CHART, A 50 Foot PIECE OF ALUMINUM GUTTER INSTALLED AT 35° F, NOT AT ALL UNUSUAL IN THE WINTER MONTHS, WILL EXPAND NEARLY ¾” BY THE END OF THE NEXT SUMMER. AS CAN ALSO BE SEEN, THE LONGER THE PIECE, THE MORE THE EXPANSION. IS IT ANY WONDER THEN, THAT LONG PIECE OF GUTTER WILL BUCKLE ALONG THE FRONT FACE OF THE GUTTER? HOW CAN WE HELP REDUCE THE PROBLEMS CAUSED BY GUTTER EXPANSION? PROPER INSTALLATION AND DESIGNING OF SYSTEMS WHICH ACCOMMODATE THIS EXPANSION ARE EASILY DONE PER THE PROPER METHODS EXPLAINED ABOVE. 

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