How to properly construct roofs over interior spaces
Exterior decks above interior space are notoriously problematic for leakage. It’s a somewhat difficult configuration to build a roof on a balcony which requires the ability to withstand foot traffic and flash and seal around a guard rail, side rails (or aide walls) and an exterior wall which joins to the interior with a door going to the balcony. Developers who redevelop existing buildings or build new buildings out of the ground with multi-family type housing are also notoriously known for breakneck schedules and poor quality construction related to low prices and low skilled subcontractors. These elements are a perfect recipe for problems and one of the most problematic areas in newly redeveloped or newly built condos or apartment buildings is leakage into interior space from balconies above. Balconies above interior space (per SF are very expensive areas to buy, sell, and build), are essentially small roofs made for people to walk on. This is an area of construction that deserves or justifies the highest levels of quality control.
The picture below shows a rare, historic type of balcony system, above an interior space. This is a flat seam copper roof system. Copper roof systems are incredibly expensive and fraught with inherent shortcomings and problems related to thermal movement resistance and poor resistance to wear related to foot traffic. Nonetheless, in historic construction, this type of copper system was one of the few options for balconies above interior space in historic construction. Balconies of this type were rare then and many have been converted over the past many more recent decades.
The balcony shown in the picture below is above a third story rear bedroom. The balcony sits in the pretty treetops of Northwest Washington, DC and creates a beautiful view and atmosphere rare in the congestion typical in the crowded DC neighborhoods. The attraction and benefit to balconies in the urban areas of Washington, DC are obvious. Outdoor space is very limited and elevated outdoor space is particularly desired. However, as mentioned, balconies above interior space are particularly complicated and the complicated construction is highly likely to be mishandled by developers and general contractors.
Flat roofs are not impossibly difficult to build, but they do require much higher levels of training and technical competence than most pitch roofs, like gable framed pitch roofs, for example. Flat roofs are more complicated for several reasons, such as:
1. Membrane attachment
Shingle roofs are simply attached with pneumatic gun-nails, flat roofs though, by comparison, need to be fully adhered or attached through plate fasteners on specific fasteners which is more complicated than simply nailing.
2. Roof penetrations
Single roof penetrations can be treated with a simple single piece flashing part which can be purchased, prefabricated.
3. Roof terminations
Roof terminations are the ends of the roof membranes, at the edges, where the roof membranes start and finish. Residential shingle roofs have relatively simple terminations such as drip edges under the edge of the shingles. By comparison, flat roofs require copings, scuppers, and metal ridge caps.
The areas of complexity above are just a short abbreviated list of the comparison between low slope roofs aka flat roofs, and residential shingle roofs.
Maintaining Flat Roof 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.
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.