Flat Roof Parapets And Coping – Part I

Next time you replace your low slope or flat roof membrane or have significant work done to repair or maintain or upkeep your flat roof, make sure to insist the contractor installs parapets copings per modern roof roof requirements, even on historic buildings.   Materials used in copings are generally made from aluminum sheet metal. Aluminum happens to work well because it is almost completely impermeable and resistant to deterioration or associated insidious oxidation from exposure to moisture in the elements.

The picture below shows an example of an aluminum coping on a rooftop parapet. The parapet extends approximately 9″ above the rooftops between two adjacent rowhomes.

flat roof parapets

We will talk about this topic over several different parts in a series, and in this first opening article we will focus on rooftop mechanical equipment items set on top of rooftop parapet coping.   In this type of assembly or configuration setting the bearing point of HVAC equipment on the parapet is extremely common.  It is often seen in urban or historic row home installations.  This type of configuration is not necessarily good or proper but it’s common because it’s one of the easiest methods of installing a large HVAC or air conditioning unit on a rooftop without penetrating the rooftop membrane for structural connections.

The picture below shows an example of a flat TPO roof bearing on an aluminum coil stock coping.  Just because it’s common does not mean it meets the code requirements though.

flat tpo roof bearing

At this specific location, there are several problems with the way that the HVAC installer installed the I-beams, the I-beams in this case are large steel structural elements that the air conditioning or HVAC contractor has used to set their equipment. In many cases, it’s not appropriate to set HVAC units directly on the rooftop deck, depending on the size of the unit and the capacity of the rooftop deck. The term ‘rooftop deck’ should also be clarified because sometimes people use the term to mean a deck like an elevated patio type structure.  Those structures are also referred to as ‘decks’, but the flat or low slope substrate system which the roof sits upon is also a deck, in the same way that a floor deck in a building is the framed structure which the floor sits upon.

How To Maintain A Flat Roof

Smart proactive replacement, construction, upkeep and maintenance of low slope roof systems requires an enthusiastic interest and understanding of waterproofing principles and building science.   Here in Washington DC, historic and modern residential and commercial buildings are extremely expensive and the roof and related systems provide the shield that preserves the building. 

We encourage all of our clients, and all readers of this article and to our blog in general, to prioritize the value of quality construction and building maintenance, and develop a relationship with our company.  You can learn a lot more on our blog.  Feel free to check it out.  If you have questions about the roof and related systems of your building in Washington DC, contact us or fill out the webform below and drop us a line.  We will be in touch if we can help.

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