Expert: Mark Sundberg - 7/29/2009

Question
Is a drip edge absolutely necessary?  If it was not installed and the roof is completed without the gutters installed, can a drip edge  be installed?

Answer
Hi Dennis,

Depends on what you mean by absolutely necessary. Will the building collapse without it? Not likely. However, the roof edge will last a lot longer. The edge of plywood, which is probably what your roof is sheathed with is the most vulnerable part of plywood, and though it's exterior grade and fairly impervious to the weather, it will suffer over the years. The drip edge prevents that by hanging down and out from the plywood edge and letting the water drip off it instead. With wood, it's likely that water will cling and encourage the growth of fungus and moss. With the drip edge, being galvanize, such growth is strongly inhibited. It's also a lot easier to replace that drip edge than it is the plywood, a lot easier.

In most cases, it should be possible to add a drip edge after the roofing is installed, though that's definitely not the recommended practice. Carefully lift the shingle edges and apply a bit of roofing cement to the edge of the decking, maybe 2" wide, and slide the drip edge in. Then you can nail it down between the gaps in the shingles. It's not the best way to go, definitely not, but if that's what you have to work with, it's better than taking up the roofing.