Advanced Insights on Surface Cracking at BUR Flat Roofs – Part II
This past week, we started looking at a built-up roof covered with a significant amount of asphaltic mastic. Here, when we say it was covered with a significant amount, we put some emphasis on the word significant, but we should explain, they applied this asphaltic mastic as if it was similar to a hot-mop type application. A hot mop application it’s applied liberally, but it’s different than asphaltic mastic because it has a much higher viscosity and has a tendency to only coat relatively thinly. Here though, by comparison, they applied so much asphaltic mastic that it built up into sheets that pooled in relatively low areas.
The problem with an asphaltic mastic, of that type, is that without being covered with a ballast or high performance reflective coating, it’s extremely susceptible to deterioration driven by exposure to ultraviolet rays. Ultraviolet rays are present in all types of typical daily sunlight, even with a moderate degree of cloud cover.
Where mastic is applied thinly, they way that hot-mop materials would generally be applied, it may peel up and erode away, with exposure to UV in sunlight. Where is applied in a buildup in a thick type of application, the mastic may have significant cracks at the surface, but in most cases will start to delaminate underneath the surface in areas where it can’t even be seen with the visual observation. That type of deterioration is arguably more problematic because when a area is deteriorated in a substrate or in an underlying area of roofing where it can’t be visually discerned or inspected, leakage of water could be occurring in places where it’s unknown
It’s almost as if it’s better to have a problem of deterioration, specifically when there’s ssociated water entry, in an area where it can be visually identified than it is to have it in an area that’s hidden. Even in some cases where the amount of water entry is more significant in the open areas.
The area across the surface of the roof simply looks rough, even from a distance. When you get closer it looks even worse. When you get close, you can see cracks and openings in the surface that you can tell are obviously potential sources of water entry. When you look back across the field of the roof from a distance, it looks like a patchwork of different colors, blacks and grays, indicating that the aluminum paint, applied sometime ago, not only didn’t adhere properly or consistently throughout the surface of the roof, but has deteriorated in unpredictable ways in inconsistent spots and locations.
In both the part of the roof shown above and in the picture below, we’re looking at the rear of the roof, where the roof gradually slopes downwards to the point that it reaches a rear drain. This rear drain, like most here in Washington DC is built with a rear termination, intended to flash into a gutter system which then drains down the rear the side of the building with a downspout.
Here and in many of the cases were shortcuts have been taken in some type of attempt to save costs through reduction of quality, they have omitted the flashing and the drip edge which should tie into that flashing to have a consistent barrier from water entry that transitions from the roof membrane to the rear gutter.
When you look closely at several different areas of the roof, you can see the specific cracks and even areas of delamination. Some of these areas of delamination are within fields of application where the bitumen mastic was applied in very thick layers. When these thick chunks break apart, they expose parts of the substrate that were intended to be covered. They were likely covered because they were suspected of leaking, sometime ago at previous iterations of repair.
The picture below shows red arrows, similar to the picture above, but in addition to the cracks that are typical from mastic fracturing from exposure to UV and cycles of temperature fluctuations, there’s an additional crack at this location below. Here, some roofer or contractor in the past, unknown to us, install a residential pipe vent boot.
It doesn’t belong here because that type of pipe vent boot is not compatible with this type of modified bitumen membrane. It’s cracked because the flange is not properly overlaid with some sort of textile backing or continuous membrane. Instead only mastic has been smeared on top and that mastic has broken up or it started to crack, coincidence with the edge of the flange.
We provide this information here on our blog, and our website, to help our customers and future clients, and 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.
Our company specializes in flat roofing here in Washington DC and we’re happy to help building owners of almost all types. 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. We are happy to help and at least talk through options.
