Nature’s reclaim! Woah-worthy examples of trees growing through a roof
Neglect and abandonment can take a heavy toll on urban buildings, particularly in cities like Washington D.C. where historic brick rowhomes are prevalent. Over time, these once-sturdy structures can deteriorate to the point where floor systems collapse, destabilizing the entire building and even affecting the exterior brick walls.
A secondary, but interesting, aspect of this deterioration process is the phenomenon of fire cuts in pocketed joists. A fire cut is an angled cut into the edge of wooden beams, allowing them to collapse with minimal impact on supporting brick walls during a fire. However, in neglected buildings where rainwater seeps in unchecked, the same principle applies. Without fire cuts, the collapse of floor systems due to rot and decay can exert enough force to destabilize the brick walls, leading to catastrophic collapses.
As rainwater infiltrates the building over many years of neglect, wooden floor systems and roof structures begin to deteriorate. This gradual decay creates openings that allow even more water to enter, accelerating the deterioration process. Eventually, the building becomes an open shell, with collapsed floors and sunlight streaming in. In such conditions, trees can take root and grow from the ground through the building, exacerbating structural damage.
Historic and modern construction techniques often rely on wooden elements such as joists, studs, plaster walls, and wood floors. While these materials were once sturdy, they are highly susceptible to rot and deterioration when exposed to unmitigated rainwater. As water ingress begins, it may seem insignificant at first, but over time, the damage compounds exponentially, leading to structural instability.
To protect against water ingress, low slope or flat roofs are commonly employed in building construction. These roofs are designed to efficiently shed water and prevent it from pooling on the roof surface. However, without regular maintenance, such as clearing debris and repairing damaged roofing materials, even the most well-built roof can fail to provide adequate protection.
Simple ongoing roof maintenance, performed on an annual or seasonal basis, can effectively prevent extreme building damage and deterioration. By addressing minor issues before they escalate, property owners can prolong the lifespan of their buildings and avoid costly repairs. In urban environments where neglect is prevalent, proactive maintenance measures are essential to preserving the architectural heritage of the cityscape.
The most common types of historic and modern low-slope/flat roof systems found on historic row homes in Washington, D.C. follow:
Built-Up Roofing (BUR): A traditional roofing system consisting of multiple layers of asphalt-saturated felt or fiberglass felts, bonded together with bitumen. Gravel or mineral granules may be embedded in the top layer for added durability. This type of roof system is one of the most calm and historic types of roofing for flat-roof buildings.
Modified Bitumen Roofing: Similar to BUR, but with added modifiers such as “rubber” or plastic to enhance flexibility and durability. Modified bitumen sheets are typically torch-applied or sometimes adhered with cold adhesives. Cold-process modified bitumen roof systems generally have much lower performance characteristics and overall modified bitumen membranes lack the high performance energy coefficients found with TPO membranes.
EPDM (Ethylene Propylene Diene Monomer) Roofing: A synthetic rubber roofing membrane commonly used on low-slope roofs. EPDM membranes are durable, weather-resistant, and available in large seamless sheets, but most often black in color and can lead to extremely high thermal gain and negative energy consequences, in Washington DC.
PVC (Polyvinyl Chloride) Roofing: A thermoplastic roofing membrane known for its strength, durability, and resistance to chemicals and UV radiation. PVC membranes are heat-welded at seams to create a seal at laps and other overlaid joints.
TPO (Thermoplastic Polyolefin) Roofing: Another thermoplastic roofing membrane similar to PVC but often much stronger, and typically white in color. TPO membranes offer excellent heat reflectivity and are environmentally friendly, extremely durable roof systems. TPO membranes are one of the best options today.
Metal Roofing: Metal roofing systems, including standing seam and flat-seam roofs, are commonly used on both historic and modern buildings. Metal roofs are durable, lightweight, and offer long-term protection against the elements, BUT modern metal roofs, in many cases do not have the same material structure as historic metal roofs and are often less durable without lead alloys.
Green Roofing: Increasingly popular in urban environments, green roofs consist of a waterproof membrane, drainage layer, growing medium, and vegetation. Green roofs provide extra insulation, reduce stormwater runoff, and improve air quality in the atmosphere.
Roof Coatings: In some cases, existing roof surfaces may be coated with reflective coatings or sealants to extend their lifespan and improve energy efficiency. These coatings are typically applied over existing roofing materials, but the are NOT roof systems themselves and they do not add life to a debilitated roof membrane, they just make good roofs last longer by decreasing the amount of damaged absorbed by exposure to ultraviolet light.
Each of these roof systems has its advantages and considerations, and the choice depends on factors such as budget, climate, building design, and desired aesthetics. Proper installation and regular maintenance are essential for ensuring the longevity and performance of any low-slope/flat roof system on historic row homes in Washington, D.C.
The deterioration of neglected urban buildings is a complex process driven by unchecked water ingress and structural decay. From destruction and rot in wooden beams to the collapse of floor systems and exterior walls, the consequences of neglect can be catastrophic. By understanding the factors contributing to deterioration and implementing proactive maintenance strategies, property owners can safeguard their buildings against the ravages of time and weather.
For effective low slope and mansard roof care in Washington, DC, chose a contractor like Dupont Roofing who has a passion for historical methodologies, waterproofing, and building science. Roofs safeguard both historic and modern buildings, which are significant investments. We urge clients and readers to prioritize quality construction, building upkeep, and consider building a connection with us. Explore our blog for more insights. If you have questions about your Washington, DC building’s roof, reach out through our webform – we’re here to help.
