Capillary break

Exterior · Windows and Doors · printed page 327 (PDF page 328)

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Book index entries

Doors and Windows – Capillary Break Doorsill Capillary Break Sill – Capillary Break and Door Capillary Break

Text in the illustration

window
sill
brick veneer
wall framing
sheathing paper
sheathing
water flow
no groove in sill underside allows water penetration and brick damage below window sill
poor
properly grooved sill
capillary break
best
caulking added at underside of sill to break surface tension and redirect water flow
better

Generated explanation

A window and wall cross-section shows a projecting sill above brick veneer, with wall framing, sheathing, and sheathing paper behind the masonry. Three enlarged details compare how water flows over the sill edge and along its underside. The poor detail has no underside groove, allowing water to travel back toward the brickwork and cause water penetration and brick damage. The better detail adds caulking beneath the sill to break surface tension and redirect water downward. The best detail uses a groove in the sill underside as a capillary break, causing runoff to drop clear of the brick below.