How to Attach Wood Drip Caps

Updated February 21, 2017

Wooden drip caps are installed on top of the exterior head casing on windows to direct water away from the window. They are held in place by exterior window and door caulk and the exterior siding. Although it is common to use aluminium or vinyl drip caps for newer homes, wooden drip caps should be installed on older homes to match the historic period of the home. If you have wood casing on your exterior windows, a wooden drip cap can provide added detail to the window and protect it from water damage at the same time.

Measure the length of the head casing on the window with a tape measure. The head casing is the top trim board on the window.

Lay the drip cap on a work surface. Measure and mark the drip cap to the measurement in step one. Place the drip cap flat on a mitre saw with the top side facing up and the back edge against the fence. Slide it over so that the edge of the pencil mark is at the edge of the saw blade. Lower the blade and move the saw through the wood in a steady motion to complete the cut.

Brush a coat of exterior primer on all sides of the cut drip cap. Allow the primer to dry for at least four hours.

Pry up the siding board just above the head casing using a flat bar. With utility shears, cut a strip of self-adhering waterproofing membrane to the length of the head casing. Apply the strip to the exterior of the home above the head casing.

Cut off the tip of the caulk tube with the built-in cutter on the caulk gun and insert it tip first into the gun. Apply a generous bead of caulk along the top back edge of the head casing.

Place the drip cap on top of the head casing and press it back against the waterproofing membrane so it rests against the membrane and head casing. Caulk along the back and side edges of the drip cap.

Replace the siding board above the head casing. Hammer the nails back into place.

Brush on two coats of exterior paint. Allow at least four hours between coats.


Select cedar or redwood if possible for the wood drip caps. Both cedar and redwood are durable and naturally rot-resistant.


Wear eye protection when installing wood drip caps.

Things You'll Need

  • Tape measure
  • Wood drip cap, 96-inches long
  • Pencil
  • Mitre saw
  • Exterior primer
  • Paintbrushes
  • Flat bar
  • Self-adhering waterproofing membrane
  • Utility shears
  • Window and door caulk
  • Hammer
  • Exterior paint
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About the Author

Jonah Morrissey has been writing for print and online publications since 2000. He began his career as a staff reporter/photographer for a weekly newspaper in upstate New York. Morrissey specializes in topics related to home-and-garden projects, green living and small business. He graduated from Saint Michael's College, earning a B.A. in political science with a minor in journalism and mass communications.