How To Tell Fake Parapets From Real

Parapets at adjoined buildings are very common, especially in rohomes throughout the historic areas of Washington DC. This week and the following week we’re going to take a look at applied or fake parapets in a multi part series.

The outline of this series of articles follows:

1. Purpose of a parapet
2. Building code requirements
3. Implications of property lines (and rights)
4. Fire separation 
5. Joining disparate roof materials 
6. Better / best practices: dimensions, continuity, combustibility, durability, structural capacity

Purpose of a parapet

Parapets serve a very important purpose to separate row home rooftops from another, where they are built side-by-side.  The three main functional purposes follow:

1. Leaks can unfurl and spread from one roof to another.
2. Fires can move between roofs without a parapet or fire rated demising wall or party-wall
3. Different roof types require a vertical surface provided by a parapet to terminate without having to be inseparably linked together.

The picture below shows an example of a real parapet, a very common type of masonry separation that rises above low slope or flat roof membranes or flat roof planar surfaces. A typical parapet comes above the plane or roof surface 12 or more inches.  Generally a parapet of this type is built from double wythe brick masonry, at typical DC brick rowhomes.  Typically once the rooftop membranes are applied to each side of the parapet, the parapet has an overall thickness of roughly 9″ to 11″, in width. An aluminum coping is most commonly used to properly cover the span of the parapet and return down vertically a few inches on each side of the top of the parapet. Copings are often omitted by cheap or low quality modern roof contractors but they copings technically required at all parapets, by the building code.

The building code is very interesting, as related to residential rowhome flat roofs and associated parapets.  The building code leaves low-slope roofs  in a bit of a gray area. The building code looks at all types of buildings and associated rules based on the zoning classification, and there’s a clear distinction, in the building code between residential and commercial type of construction assemblies. Flat roofs are mostly regulated and specifically marketed by manufacturers for installation on commercial or industrial buildings. There is no specific market, as driven by manufacturers, to focus on residential installations of flat roofs.  Instead, manufacturers consider this a commercial product.

So, this gray area is very interesting because we have commercial products being installed on residential buildings, with the building code designed to directly address 90%+ building assemblies of residential buildings in the western world, not just urban row homes with flat roofs.  However, it’s interesting because the building code has less than a dozen pages written to govern the standards for installation of each type of commercial roof material or system on a residential building.  It’s basic an unintended but critical hole or omission in the building code.   DCRA and AHJ inspectors do not execute enforcement of the rules of the building code on flat roofs.   DCRA has been heavily criticized in the past for not enforcing contractors, particularly flippers and quick, hard-money driven developers, to follow the building code.  These are all some of the many reasons it’s important to have a well trained and quality focused contractor install and maintain a flat roof.

A picture of a fake parapet follows below. Although we refer to it as a fake parapet, it’s essentially serving half of the characteristics or traits and benefits we expect from a parapet but it’s an applied parapet, it’s not actually cladding or covering a masonry parapet wall, so there’s no consistent fire separation and the applied parapet is not a continuation of the building structure.

Maintainance of Flat Roofing Systems

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. 

Unlike the majority of roofing contractors, as we can clearly see from the conditions abundant throughout the city, our company cares about quality and the longevity of your roof and building.    The biggest difference overall though, is knowledge and understanding. Often, we look at the near limitless amount of poor workmanship done by other roofers throughout the flat roofs of the city. It’s a complicated issue.   It’s easy to dismiss the issue and simply say they’re bad contractors, but that’s a lazy way of looking at the context. There’s more to it than that period often, the vast majority of work that we consider to be defective, lacking in longevity, poor quality or poor workmanship is actually work that was done using expensive materials and onerous amounts of labor.  The work wasn’t done poorly to save materials or time, it was done poorly because the roofer didn’t know better.  No one’s perfect, but our company is significantly different.   We have been trained and educated on the technical fundamentals of building science and understand the principles of best practices.  Decisions are case by case and a makeshift approach can be significantly pragmatic in certain circumstances, but it’s beneficial to every building owner and stakeholder to choose a roofing contractor who cares about building conscientiously using knowledge as a guide.

Quality work of this type can make a big impact and positive difference. Investments into good quality construction have a positive return on investment and avoid the need for continued mitigation of unexpected or unplanned problems throughout the life of 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, fill out the webform below and drop us a line.  We will be in touch if we can help.