Today we’re looking at a roof that is completely overgrown with vines and tree branches. Below this giant heap of vegetation and plant growth, there’s a typically configured flat roof. like most roofs we see in Washington DC on a regular basis. Typical roof layouts for the thousands of historic row homes throughout Washington DC are relatively consistent in the general layout. There are variations in the length and width and layout of parapets, and layout of the rear ell at the rear part of the buildings, but generally, most things are relatively consistent with slight variation or different categories of general configurations.
Here in the picture below, looking from about the middle of the roof, towards the rear, you can see the entirety of the rear area of the roof next to the rear ell is completely covered with this overgrown vegetation. The roof is in terrible shape and needs drastic upkeep and repair. Flat roofs simply need to be maintained and have relatively simple upkeep performed on a routine basis. The amount of upkeep varies from one type or category of roof classification to the next. Modbit roofs need more upkeep than TPO roofs, for example, but all of them need a degree of upkeep and maintenance. Some of them just at least need to be checked on a regular basis to make sure that gutters haven’t filled with leaves and to see squirrels haven’t pried a drip edge apart from a fascia or rake board and birds haven’t found a way into a spark arrestor. These simple things are easy but they need to be done on a routine basis because once problems begin, they get worse, exponentially. Those things are typical, but today we’re looking at a roof that is way beyond the condition of normal upkeep and maintenance, it needs extensive repair and restoration.
The next picture below shows the same area of the same roof but from a different angle. You can see that there are piles of bricks scattered around on the rooftop, near the parapet. It’s likely at some time in the past, somebody had done work on the chimney repair but, to either make repairs, or to rebuild something that had been dilapidated or partially defunct after significant time had passed without upkeep and care. We often find bricks and old abandoned building materials strewn about on flat roofs. These type of materials don’t necessarily ruin or destroy the roof surface, but it’s better to have contractors who simply get that they shouldn’t leave materials on a rooftop, and technically, from a building code and building material manufacture perspective, leaving materials abandoned on a roof can cause damage through slight micro movements that happen all the time which can lead to wearing out spots of the low slope roof.
Various parts of a low-slope roof, including rear terminations, copings at demising wall parapets, seams or gaps at typical laps in roofing membranes, and access hatch or scuttle hole lid covers. These parts of the roof are particularly susceptible to plant invasion due to their structural characteristics and potential vulnerabilities in the roofing materials. Other parts of low-slope roofs that are prone to plant growth include roof drains, perimeter flashings, and around HVAC units or other rooftop equipment.
Plants cause damage to roofing systems primarily through their growth mechanisms. Initially, small branches and vines can find and wiggle their way into tiny openings or weaknesses in the roofing material. The locations of the most common entry points are normally around the terminations or edges of the roof but internal or Field located successive overlaps can also be a point of plant entry. Unlike precipitation and water, which generally follow the flow of water / gravity, even in typical cases plants are less controlled by gravity. They ca grow and reach out upwards like tentacles. As these plants grow, their cellular structure transitions from soft, green tissue to more woody or cellulose-based tissue. This woody growth exerts increasing pressure on the surrounding building materials. Over time, the expanding plant matter can push apart these materials, creating larger gaps and exacerbating existing vulnerabilities.
The damage caused by plants is often compounded by their ability to direct and concentrate water flow. As plants grow into the roof structure, they can disrupt the intended water drainage pathways, leading to water infiltration. Water can then be funneled into the building through the newly created gaps, causing interior damage and contributing to the deterioration of the roof structure. This can result in rot, mold growth, and compromised insulation, further accelerating the rate of damage.
In this way, plants can damage roofing and building materials exponentially. As initial damage occurs, the affected area becomes more susceptible to further plant invasion and water infiltration. This leads to a cycle of deterioration, where each stage of damage makes the roof increasingly vulnerable to the next. Over time, small infiltrations by plants can lead to significant structural damage, necessitating costly repairs or even complete roof replacement.
Routine upkeep and maintenance are essential in preventing this type of damage. Regular trimming of nearby trees and vines helps to minimize the risk of plants reaching the roof. Professional roofing check-ups should be conducted routinely to identify and address any plant growth where such growth is not visible from the ground. These inspections can help to see that any potential points of entry which plants could otherwise exploit are promptly sealed and that the roof remains in good condition. By proactively managing plant growth and maintaining the roof, the risk of plant-related damage can be significantly reduced.
In this coming week, we’ll take another look at this same building’s roof. It happens to be a historic and old built up roof. It’s one of the few types of historic roofing that worked effectively on low slope roofs. Today this type of roofing is rarely ever used because, arguably, much better options are found throughout the industry in single-ply membranes.
We recommend every building owner in DC who values the longevity of their roof (and their investments) and building use a contractor who values the simple and important principles of proper roof construction like Dupont Roofing DC. Learn more about our company and the proper techniques of working with roofing on historic buildings in Washington DC here on our blog at DupontRoofingDC.com, and you can call us at (202) 840-8698 and email us at dupontroofingdc@gmail.com.
