Foam coatings for flat roofs are generally added as part of repairs or renovation of an existing roof, and the durability of the foam allows it to last for years with minimal maintenance. However, small holes and cracks will eventually appear in the foam's surface after enough time passes due to falling branches, hail, birds, and other common roof hazards. Using these tips to patch small damaged spots on your foam-coated roof will give you the best possible results to prevent leaks.
Don't Forget Rising Moisture
Many foam roof coatings form visible blisters that look like rising bubbles on the surface of water. It's essential to discover the specific cause of this kind of damage to prevent it from reoccurring in the future, but many homeowners and professionals alike overlook the potential for moisture to seep into the foam from below. This could be due to a leaky pipe in the ceiling or attic, or a moisture-generating room like a bathroom that was designed with insufficient vapor barrier between the interior space and the roof above it. Check for signs of moisture under the foam and roof, not just from above it, when trying to troubleshoot the cause of blistering.
Cover Exposed Foam Immediately
It's true that a leak that begins at the surface of a foam roof coating can only damage the underlying structure if it makes it under the substrate between the foam and the roof deck. However, this isn't an excuse for leaving parts of your roof foam in poor condition, especially when the foam itself is exposed due to a missing coating. These otherwise durable roof foams deteriorate quickly when exposed to the UV rays in sunlight, so make sure any exposed foam is covered at least with a tarp or other temporary cover until you can complete the patching process.
Remove Damaged Material
Many attempts at patching a foam roof coating fail because too much of the worn and damaged material is left behind when new coatings are applied. Any brittle, cracked, flaking, or other worn coating and foam should be scraped and cut away until only intact and quality materials are visible. These intact materials should also be roughened to encourage a strong bond between the old materials and the new material added during patching. Taking extra care to prepare each patch site—much like a dentist prepares a tooth with a cavity for a filling—pays off by creating a durable and long-lasting repair.
Avoid Unnecessary Patching
Not every rising blister or sunken spot on a roof's foam layer requires immediate attention. In fact, patching a section of roof that looks damaged but is still intact can actually cause leaks that would have otherwise never existed. Have each part of the roof inspected by a professional before assuming it's really damaged and in need of repair. Many repair companies are happy to do any patching you would like whether it's necessary or not, so pay a second party to verify if the repairs are worth spending money on first.
Prepare for Curing
Many small and limited areas of damage to a foam roof coating are caused by mistakes made during the installation process rather than damage that occurred due to bad weather or maintenance mistakes. The spray foams and stretchy outer coatings used in repairing older roofs produce a lot of moisture when curing and hardening, and applying different materials too quickly results in a pool of water gathering on the roof long before the first rain storm. Set aside plenty of time for curing the various layers of material used in the patch as well so you don't accidentally compromise the durability of the patch by trapping moisture inside it.