In last week’s article on our blog, we took a look at several different standing seam metal roofs here in Washington DC and talked about the methods of installation, and details related to upkeep and maintenance and particular examples of severe to moderate oxidation. Today, we’re going to look at some other examples of standing seam flat roofs and talk about some of the topics related to energy considerations on metal roofs, recoatings and alternatives for upkeep and or replacement.
In last week’s blog article on our website we also took a look at some of the different types of metals that are commonly used in standing seam metal roofs and we discussed some of the details of copper standing seam metal roofs.
Although, here in Washington, DC, so many of the standing seam metal roofs that remain from historic times, are on the tops of the buildings where they can’t be seen from the public view, they can still look good. In fact, in modern times, one of the few remaining good reasons to use standing seam metal roofs for a new installation is to place it in a location where it’s visually prominent. The standing seam metal roof doesn’t blend with all styles of architecture, but in some places it provides a nice visual accent.
The picture below shows a standing seam copper roof in an area of a stone built ashlar masonry church. The remainder of the building roof is slate stone tiles which looks much better, yet the copper standing seam room shown here provides a nice looking accent.
Standing seam roofs do not work as well though, for a variety of reasons. One of the big problems with historic standing seam roofs is that they were generally built or manufactured with a ferrous alloy metal. The ferrous metal alloy roof is one that contains iron. One of the shortcomings of iron, although it is very strong, is that iron will oxidize and rust if not fastidiously maintained and kept under a good coat of paint.
In the picture above, you can see that where the low slope roof nears the rear termination, it happens to be coincident with an area that is shaded by a tree. The shaded area dries out very slowly and also coincidentally happens to be an area where leaves will build up. Since this area is particularly shallow and leaves will pile up and build in those areas, it stays hydrated much longer than it would if it were in a area that was exposed to more hours of daily cycles of sunlight.
On this roof, because of the layout, rainwater happens to flow, at each precipitation cycle, more directly in between the standing seams and as water saturates the leaves at the standing seams, there’s rust or oxidation that occurs on each side of each standing seam. Just as in areas of ponding, as water builds up and has slower dry times, the paint will deteriorate and delaminate at a higher rate than at other areas. Here the paint has delaminated and exposed the layers of old terne roof paint and areas of bare metal. These areas are now rustier than they would be otherwise.
At another similar roof assembly, the metal surface of the roof has been well maintained and aside from small spots of delamination and rust, it remains in condition, even after decades of service life.
There are several different types of roof paints, and for the decades which predated the current era of material development, one of the few good options for roof paint available was aluminum paint. Aluminum paint is generally solvent based and bonds well to most roof substrates but has lower reflectivity and lower elasticity then other types of coatings such as silicone and or even elastomeric coatings.
Penetrations through metal roofs rely on low viscosity fluid sealants or direct soldering but in most cases direct soldering is not the best option, depending on the substrate or the material of the pipe or penetration through the roof. Not all materials are acceptable substrates for soldering and soldering also creates a binding point which restricts required tolerances for movement in some areas or configurations of metal roofing.
In a picture below, you can see an example of a plumbing vent pipe that passes through the low slope standing seam metal roof.
We recommend every building owner in DC who values the longevity of their roof (and their investments) and building use a contractor who values the simple and important principles of proper roof construction like Dupont Roofing DC. Learn more about our company and the proper techniques of working with roofing on historic buildings in Washington DC here on our blog at DupontRoofingDC.com, and you can call us at (202) 840-8698 and email us at dupontroofingdc@gmail.com.
