Looking Behind A Historic Water Table – Part II

In a recent article on the same topic, we showed examples of a historic brick building where the projecting water table had deteriorated and collapsed.  Today we are looking at neighboring buildings built in the same style with water tables still intact, nonetheless less though with flat roof problems caused by cheap contractors cutting corners on quality. 

front facade water table
A neighboring house with the front facade water table still intact provides a comparative point of reference.

Of note is the nonlinearity in the relationship between water damage and its impact over time. Once water infiltrates a structure, it initiates a cascade of deterioration that can accelerate with surprising swiftness. This phenomenon is reminiscent of a domino effect, wherein initial damage serves as a catalyst for subsequent harm. Cracks and erosion, once established, propagate at an escalating rate as moisture infiltration continues unabated, paralleling a geometric progression.

These architectural details are prevalent in neighborhoods like Capitol Hill, Dupont Circle and Georgetown. While architecturally significant, these details were built with materials available over 100 years ago and these materials lack the water resistance of modern synthetic and polymers today.  Although the original water tables offer a measure of protection, the inherent limitations of antiquated materials render them susceptible to the challenges presented by contemporary climate variations. Intensified weather events, characterized by elevated precipitation and flooding, exacerbate the vulnerability of these structures. While the utilization of water tables and analogous architectural features remains pivotal, their efficacy hinges on consistent maintenance to ensure their continued integrity.

By comparison, polymers, especially those used in the most common and advanced single-ply roof membranes such as TPO, EMPD, and Modified bitumen membranes have high resistance to water infiltration or water caused deterioration.   Polymers have advanced water resistance due to their molecular structure, which often includes hydrophobic regions that repel water molecules. The tightly bonded polymer chains create a barrier that prevents water infiltration, contributing to their effective water-resistant properties.  The inherent shortcoming though is that these materials often lack one or more of a few important characteristics found as native qualities in some historic materials.  For example, brick masonry, and even concrete mayurakly us highly resistant to the deleterious effects of exposure to ultraviolet light rays, yet polymers are highly susceptible to degradation or deterioration from exposure to UV.

deteriorated asphaltic overlay
The deteriorated asphaltic overlay at this short-cut of a roof repair shows the shortcomings of inexperienced non-professionals having access to cheap products at big box stores.  It’d be better for property owners if cheap contractors just didn’t exist.  However the photo shows a quintessential example of asphaltic sealants degrading at a highly accelerated rate because of their inherent weakness to UV exposure.

Notably, the contemporary context of climate change introduces an added layer of complexity. The heightened frequency and intensity of adverse weather patterns pose amplified threats to these historic facades. The efficacy of water tables, while pivotal, is contingent on ongoing preservation. To manage the preservation of these architectural and significantly aged elements, sustained and continuing upkeep and maintenance of protective features are imperative in mitigating water-induced damage and safeguarding the built environment of our DC historic buildings.

modified bitumen roof membrane
If you look at the top of the sidewall down the alley, a modified bitumen roof membrane has been laid over the top of the parapet.  At the time of original construction wood elements were embedded into the brickwork to attach the roof materials.  Craftsmanship of this type is almost lost today with cheap shortcuts by the majority of contractors.

Smart proactive replacement, construction, upkeep and maintenance of low slope roof and mansard roof systems requires an enthusiastic interest and understanding of historical methodologies, 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, it’s quick and easy.  We will be in touch if we can help.

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