Enhancing Stability on Low-Slope Roofs with Aggregate Ballasts
This past week, we began looking at similar images of a low slope roof with an aggregate ballast placed on top of the roof to provide a weight where the roof membrane was not fully adhered. Ballasting systems like this aggregate stone can help prevent the rooftop from uplift or even tear off during heavy winds. There’s other benefits to aggregate balance as well though.
Aggregate ballast systems like this can also protect the substrate roof membrane from accelerated deterioration related to exposure to ultraviolet rays in sunlight. Ultraviolet rays like this are ever present in typical sunlight, and danage materials. Often, ultraviolet rays will deteriorate organic and carbon-based type materials, very rapidly. Most typical modern single-ply membranes have a degree of resistance to deterioration from ultraviolet exposure, but even the synthetic or polymer type materials will also be damaged and eventually destroyed by exposure to ultraviolet rays.
Although we don’t recommend aggregate stone to be installed on top of most modern single-ply polymer type systems, we still recognize that materials like this will significantly deter or slow deterioration because it limits the amount of exposure of ultraviolet down to the level of the rooftop membrane of light a rock or natural stone type surface, the stone absorbs that energy, but in most cases is largely unharmed by the exposure to the ultraviolet rays. The other types of materials common in building construction, by comparison, are generally very sensitive.
Wood, rubbers, plastics, and many other types of common substrate building materials are very heavily negatively affected by exposure ultraviolet rays. Here, the stone aggregate ballast protects the loose laid roofing, to a large extent.
Aggregates on rooftops also provide a degree of fire protection to most buildings, in some typical installation scenarios. The majority of provisions in building construction to prevent the spread of fire occur at classified partitions and classified building assemblies which have fire ratings to contain fires within themselves. In some cases, those particular ratings are also intended to provide fire from entering from the outside, but not as many provisions are built directly into the building code to prevent fire from entering from the outside shell to the inside of a building.
In this particular case though, the aggregate ballast does provide a resistance against fire from the outside. Like brick masonry construction, most types of stone used in building construction will not burn or combust in a way that will spread a fire.
This past week, we described the layout and showed the location of one of the internal roof drains. Here in the next picture below though, you can see the dome strainer or the screen that has been installed at one of those drains, more closely. The dome strainer essentially helps water flow into the drain system without allowing the majority of the larger debris to enter into the plumbing and piping system.
Although aggregates in stone generally have a relatively low resistance rating from an insulative perspective, they still can add a degree of thermal separation. Without proper preparation, an enormous amount of energy can be absorbed through the roof in the summertime and enormous amount of energy used can be lost through the roof in the winter time.
The heat energy absorbed during the summer months, particularly here in Washington DC, have a very negative impact on the heating and cooling energy load. Unlike energy that’s used for positive purposes, the heat energy absorbed through a roof in the summer is not captured and used in a positive way by the building. Instead, the cooling system of a commercial building must almost instantaneously fight against the solar gain or thermal load to cool the space in a reactionary sort of way. Cooling large commercial buildings can be extremely expensive and of course these expenses are also set in parallel to a carbon footprint which affects the future of our environment.
Additional thermal resistance, either in the form of insulation, or in this case in the form of the ballast on top of the roof surface can significantly help deter and or reduce the amount of energy burden from the Sun as solar gain is absorbed by the building’s roof. This is really useful because it has a serious economic impact and a drastic environmental impact. It also improves the quality of use of the interior of the building. Cooler buildings, especially in the hot summers here in Washington DC, are much more comfortable for the occupants or users of the building
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.
