Shield Your Roof from Harmful UV Exposure
The closer view follows below. We should mention though just for clarification and disambiguation, there’s another type of modified bitumen system which is called ‘granulated’. The granulated modified bitumen is manufactured with thousands of small granules of ceramic materials that are set onto the surface of the membrane. Those granules essentially create a UV resistant layer of materials on top of the modified bitumen membrane, similar to paint, but the granules, by comparison are not intended to be painted. This is basically an example of a different type of modified bitumen system which doesn’t need the constant ongoing repeated cycles of repainting. The maintenance requirements therein are much simpler.
As you look closer at the modified bitumen smooth roof shown in these pictures, here today, you can see signs of deterioration. There are also signs that there is delamination, fish mouthing, and or undulation in the surface of the modified bitumen membrane. These types of defects generally can be traced back to errors or defects in the installation of the membrane. Substrate preparation is extremely important in the initial installation of almost any type of roof system. Low cost or low quality roof contractors are notorious for skipping many of the steps required for proper preparation.
Modified bitumen membrane materials, if installed new, are generally manufactured and sold on rolls that are long enough to accomplish or fulfill the required length of at least a few courses of a typical span rooftop. In this case though they installed many seams right in the middle of the latitudinal run across the rooftop. Often, low-cost contractors will use scrap materials to install new roofs.
Those materials are not necessarily salvaged, but they may be scraps or leftover remnants from other roof installations. We believe in recycling and the principles of reuse and limiting waste, where practical and where it doesn’t hurt or detract from the quality or longevity of a new installation. However, reusing remnant materials doesn’t meet the specifications of all construction projects and may have problems that lead to issues with quality such as this type of installation where seams are run in-line.
We’re not sure why this original roofer used smaller pieces and then joined them together in the middle of the roof, but if you look closely you can see a seam that runs concurrently from one course of membrane to the next. There’s a few problems with this type of seam. First, seams should always be staggered, it isn’t necessarily critical, but it’s best practice to offset seams from one course of roofing in the latitudinal direction to the next.
It’s helpful to create an offset like that because if there is leakage between interstitial layers of membrane for any reason, at least at the overlap, a leak will not transpose or filter from one area of membrane to the one below. The same principle applies in residential roofing. There’s always butt joints which essentially work like a seam between two different shingles. You always put that seam over top of the middle of an uninterrupted or complete portion of shingle below. That way, if water makes its way between those two pieces of shingles, it stays on top of the uninterrupted surface below.
Here though, the contractor put seams directly in line from one course of roll membrane to the next. They shouldn’t have done that.
We assume that the undulation or waviness in the surface of the roof membrane is caused by improper welding of the modified bitumen membrane or related to a deteriorated substrate material.
When you look very closely, you can see significant alligatoring in the surface of the membrane. That term of alligator means that the roof membrane is beginning to deteriorate and come apart at the upper surface where it is exposed to UV rays in everyday sunlight. Over time, without a coating on top of the modified bitumen membrane, the UV rays will degrade and deteriorate the roofing materials. Depending on a variety of factors such as shade from trees versus the amount of direct sunlight, UV exposure, without painting, can shorten the durability of a roof down to only half of its intended lifespan.
The next two pictures look even closer at this membrane, and you can see the level of deterioration very clearly.
Low slope roofs require lots of labor for installation and therefore are simply expensive. We would always recommend that these modified bitumen roof membrane systems be painted within at least 3 to 6 months after initial installation to help protect the membrane from the advanced and accelerated deterioration caused by exposure to sunlight without a coating. Otherwise, you’re basically throwing away a significant part of the investment that you’ve made into installation of the roof system.
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.
