Alternative Roof Types: Corrugated Metal Roofs – Part II

This past Monday we looked at a few different corrugated metal roof and talked about some of the principles behind using this type of material in modern buildings.

The outline of these 2 combined articles follows below and today we will focus on items number 4 – 6.

Alternative Roof Types: Corrugated Metal Roofs

    1. Comparison Between Corrugated Metal Roofs and Standing Seam Roofs
    2. Fire Resistance 
    3. Material Options
    4. Required Maintenance
    5. Suitability for Low Slopes  Corrugated metal roofs can be installed on roofs with low slopes, offering versatility in design.
    6. Limitations 
gable style roof
In our last article, we looked at the roof shown in the picture above from different angles. This is a gable style roof with one ridge and two eaves, even though there are no built gables because this is an open building much like a Dutch barn.

Required Maintenance

Like all building materials, even types of low maintenance roofing systems like corrugated galvanized steel roofing panels, still require maintenance from time to time. A interesting parallel is TPO roof systems. TPO roof systems are generally a bright white color which has high reflectivity and unlike modified bitumen low slope or flat roof systems the TPO roof systems require very little maintenance. Nonetheless, even though some vendors market them as “maintenance-free” roof systems, they still do require maintenance.

Even without having to do laborious recotings, TPO system, for example, like many other single-ply roofing systems, require redundant applications of sealants at joints between the edges of the roof and adjacent building systems. Chimneys and counterflashing or termination bars are a quintessential example. While the roof itself needs little upkeep in maintenance, areas like this have to be re-applied at least every couple years.

Galvanized corrugated sheet metal roof systems are similar in this way. They require very little upkeep and maintenance, but gutters need to be kept clean and a seasonal check up should be applied. Also the edges if not well treated at the time of cutting or installation will need to be recoated. In the picture below you can see an area at the edge of the panels where oxidation of the ferrous metal has turned the area of galvanization on the underside of the panel a red color.

redundant overlap penalized roof materials
At the panel edge, you can see the redundant overlap of the panelized roof materials.

The alternating upper and lower edge of the corrugation, at the upper edge, provides a location where the overlap is relatively effective in stopping most typical precipitation events from leaking through the seam. This almost works well by gravity alone, but geographic areas and geographic specific climate zones have a lot to do with the performance of these type of systems because they will not work well in areas where temperatures go below freezing, especially over sensitive areas such as interior spaces.

Suitability for Low Slopes

Above, we mentioned that these systems may not be well suited for areas that have temperatures below freezing, but with relatively high or at least moderate slope roofs, these systems can generally work better than in a horizontal or low slope position, even with precipitation in an environment that goes below freezing.

cordiate root system
The wider angle of view in the picture above shows the greater expanse of a cordiate root system.

The next picture below shows an example of a fastener, installed through the high ridge of the corrugation system into a purlin below.  It’s very important that any fasteners like this both have a integral neoprene gasket as shown in the photo below and also that fasteners are installed in the upper ridge of corrugation, not the lower area.

roof fastner

Limitations

Above, we mentioned that these type of roof systems are not really applicable or the best candidate for installation in cold climates, even climates like ours where we have hot summers, but we have winter temperatures that go below freezing.  Ice damming can occur and backup into seem areas, when the roof system is entirely covered with a heavy yet melting snow, for example.

limitations of corrugated roof systems

Upkeep, Care and Maintenance of Washington DC Historic Roofs

It’s worth noting that while many of the historic methods of roofing do not work well in our climate zone, the principles of this type of building design and engineering highlight the fundamental principles of our roof flat and mansard roof design here in Washington DC. Consulting with a roofing professional, like Dupont Roofing, familiar with the specific climate conditions and the building science of roofing in Washington DC is advisable to ensure the roof assembly is appropriately designed and constructed to manage the flow of water, ice damming, capillary action and condensation effectively.

The upkeep, maintenance, and general care of flat and mansard roof systems should be driven by an understanding and passion for historical methodologies, waterproofing principles, engineering and building science. Washington DC, a city built with both vintage charm and contemporary modernities, residential and commercial buildings of substantial value. 

The roofs of these buildings are their defensive shield from the harsh elements of nature. To our clients, as well as all readers of this article and our blog, we emphasize the importance of quality construction and active building maintenance.  Our website includes informative resources you can use to understand and learn about best practices on preservation of your building.  If you are in need of further guidance on the roof and its associated systems for your Washington DC property, we are here to assist, where we can. Simply contact us or complete the webform below and drop us a line and we’ll respond if we can help.

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