A drip groove (also called a drip edge, drip nose or throat) is a narrow channel or projecting ridge on the underside of a sill, coping or string course that forces rainwater to detach and drip downward instead of running back along the facade.
How it works
Water flowing over a horizontal or sloping surface tends to creep along the underside by capillary action. A drip groove interrupts this water film:
- Water flows across the sill or coping to the underside
- At the drip groove the water is forced to detach
- The water drips downward, away from the facade
Without a drip groove, water would track back to the wall face and cause staining, dampness and deterioration.
Application
Drip grooves are found on:
- Weathering sills — the underside of a concrete or stone sill always has a drip groove
- Window sills — projecting sills have a drip groove to keep the facade dry
- String courses — horizontal mouldings in the facade with a drip groove on the underside
- Window frames — timber and aluminium profiles have a routed groove serving as a drip
- Concrete overhangs — cantilevered sections are given a rebate to act as a drip groove
Related terms
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