A drip edge is required at the eave and rake edge of a shingled roof. This is mandated by the International Residential Code 2015 NJ Edition Section R905.2.8.5. Prior to this code a drip edge was not mentioned (well it did get mentioned in the 2012 IRC but New Jersey never adopted that code). The drip edge could have been enforced under the general statement of Section R903 Weather Protection where it states the “assembly shall serve to protect the building or structure”. But I assume the code writers felt this was just not enough.
What is a drip edge? It is defined as a metal flashing located at the roof edge that helps keep the water from infiltrating your roof edge. It can also protect the roof edge from insect damage. The importance of the drip edge is threefold it improves the efficiency of shedding the water away from building components, it assists and protects the structure in the movement caused by expansion between the roof deck and the fascia board and it gives your home a more finished appearance.
A drip edge is a non-corrosive typically 36 gauge angled piece of metal that gets tucked under your shingles at the roof edge. The code requires the drip edge to be mechanically fastened (not adhered) directly to the roof deck at the eaves and then the underlayment goes above it, however at the rake (the sloped side of a gable) of a roof the drip edge gets installed above the underlayment. The code specifies the required overlaps and minimum measurements for this critical piece of flashing.
In the past contractors believed by just extending out your shingles beyond the fascia would be sufficient in shedding the water away, but this is a construction myth and is a poor practice of creating a method that will fail in protecting your home.
Do you still need a drip edge if you have gutters? The answer is yes! The gutter will tuck behind the drip edge giving you maximum protection to your roof deck structure.
A cousin of the drip edge is the drip cap. This item gets installed above your windows and exterior doors and serves in the same capacity of diverting water away from the underlying structure. The drip cap is more elusive in the code. For this piece of flashing the code does not specifically call it out as the drip edge but lays down a general requirement of Section R703.4 Flashing. The burden falls on the window manufacturers’ instructions and the design professional. Many manufacturers have integral flashing built into their windows affording you the protection required.
The code requires flashing in many locations of your home to insure weather tightness of your structure and protecting your wallet. Ask your architect and contractor to make sure your construction project is being properly flashed and let your local building official no any of your concerns.