How should a drip edge be installed at the eave?

The appropriate method for installing a drip edge at the eave is to place it under the underlayment. This technique ensures that any water that flows down the roof and encounters the drip edge is directed away from the underlying structure, which helps prevent moisture intrusion. By positioning the drip edge underneath the underlayment, you create a water-tight barrier that enhances drainage and protects the roof's components from potential damage caused by water infiltration.

When the underlayment is installed over the drip edge, any water that seeps under the underlayment can potentially reach vulnerable areas such as the roof deck or insulation. This positioning would negate the protective purpose of the drip edge, allowing water to sit and possibly lead to leaks or rot. Therefore, installing the drip edge under the underlayment is a crucial step in roofing to maintain the integrity of the roof system.