The main purpose of a roof is to keep the interior of a building warm and dry. But, it also keeps the moisture flowing down the roof away from the walls and foundations. To do so it must manage capillary action, which might otherwise cause water to flow inward, and even enter the attic space. Roof overhangs and drip edges may be elegant ways to achieve this.

Roof Overhangs First, Then Drip Edges

Roof edges are the lowest part of a roof that extend beyond the outside of a building. A soffit may or may not enclose the space beneath, and the extent of the overhang depends on the architectural style. The main functions of this essential structure are as follows:

• Protect the building from strong winds and heavy rain.
• Provide extra shade to windows, reducing heat and glare.
• Keep the interior of the house comfortable in summer.

The depth of a roof overhang depends on the local climate. A designer may be able to reduce the cost, by shortening this in a dry environment. However, roof overhangs may extend by as much as two feet in a wet climate. But the crunch point remains the lower edge of the roof overhang. What happens to the water then?

Drip Edges Steer the Water off the Roof

Eaves troughs catch rain water, and lead it to down pipes that channel it away. However, capillary action may counter this to an extent, by following the underside of the roof itself. Drip edges are supposed to prevent this happening, by managing the phenomenon.

The primary drip edge is the lower surface of the bottom row of asphalt tiles, or other roof covering. A steel roof may readily achieve this, however the lower edges of asphalt tiles may encourage the moisture to worm its way beneath them. One simple way to manage this is to fit a separate drip edge. But what exactly is that?

A drip edge is a piece of flashing that attaches to the lowest part of the roof sheathing, in effect extending this slightly. The asphalt tiles or other roof surface lay over it, all but concealing it as it delivers the water accurately to the eaves troughs.

Support Available from Valiant Exteriors in Calgary

Homes built a while ago came standard with drip edging. However, many modern constructors overlook this simple solution. Back-fitting drip edging may be your solution to moisture dripping from your eaves troughs, and potentially damaging your roof overhang and soffits.

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More Information

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Roof Edge Protection Illustrated (Energy.Gov BY US Government Work)