11/18/2022
Notes from the field.
So, this is not how to start your rooftop garden.
Ethylene propylene diene terpolymer (EPDM, also referred to as rubber roof membrane) roof coverings are widely used on both residential and commercial structures with low-slope roofs. There are plenty of benefits and advantages to this roof covering, but one disadvantage is its vulnerability to puncture damage. This is especially true towards the end of its service life, when shrinkage pulls the membrane tight as a drum instead of adhering firmly to the roof deck.
What we're seeing in these photos is a tear and displaced flap in the membrane, with the flap opening oriented towards the upslope of the roof. The significance of this detail is that rainwater running off the roof will catch this open flap and contact the roof deck beneath the roof covering (though to be fair, this water damage was inevitable regardless of the flap orientation).
The plant life growing through this tear was a nice touch, but the underlying condition is concerning. I deduced that there was significant moisture-induced rot of at least the roof deck sheathing in order for plants to find suitable conditions for growth, and walking this part of the roof was hazardous because of how poorly supporting, spongy, and deteriorated the underlying roof deck was. I would have put my foot straight through the roof if I applied my entire weight on certain areas.
My recommendation to the client was to bring in a roofer immediately to do a more invasive assessment of this section of the roof, and to be prepared for bad news that could include at a minimum replacing the roof covering and sheathing. I wouldn't be surprised if rafters or other structural components had also been compromised by water damage. It is so important to periodically inspect the roof in order to detect and correct roof covering defects, so as to spare the heartache of damage to this extent.
As an added bonus, the last photo shows a large rock holding down a corner of an improvised repair to the EPDM membrane. First of all, there are excellent adhesives available specifically for this exact application. Second, the front porch and sidewalk are below this roof. I don't think I need to explain why you shouldn't place large, heavy, unstable objects on roof slopes overlooking walkways...