Drip Edge: What & Why?

April 9, 2021

Drip edge is one of those roof components that often goes unnoticed by homeowners which is probably leading you to ask, “What is drip edge, and what is its purpose?”


Drip edge is a thin sheet of metal (aluminum, galvanized steel, or copper) that is fastened to the eaves of your roof. 
If a homeowner chose a drip edge purely for functionality, it could be difficult to spot. If you look along the edges of your roof, underneath the 2-inch shingle overhang, you will notice a strip of metal. 
drip edge being pointed to by contractor


Roofing might seem simple but it has a lot of science involved. And the topic of today is: ADHESION
Adhesion is one of the two unique properties of water (along with cohesion... don't worry about that one for this). This property is simply defined as the attraction to other substances.
difference between adhesion and cohesion

I know it looks childish, but this is possibly the best illustration I have ever found to describe the adhesion and cohesion properties of water. Adhesion causes water to stick to other surfaces, while cohesion causes other water molecules to stay attracted to one another.

Now let's tie this together to explain what drip edge does for your home. As water runs off your shingles, not all of it drips off that 2-inch overhang.

Since water has strong adhesion forces, some water will want to stick to the underside of the shingle and run back UP the shingle towards your home. 

You might think it's hard to believe water running upwards, but roll up a paper towel and stick the tip of it into a cup of water. That water runs right up that paper towel (by the way, this is how plants work: sending water from the ground up to the top).

I know, I know, I'll stop with the science.

So now water is running back towards your home on the UNDERSIDE of your shingle. EESH! 

drip edge keeps water from running back up your shingles

Without drip edge, the water can penetrate between your shingle and your roof decking causing your roof deck to rot. It will also then begin making it’s way into your fascia causing it to rot as well.

Drip edge catches that water traveling on the underside of your shingles and diverts it downward, off your roof, and onto the ground.


I mentioned "purely functional" before because a lot of trendy homeowners might choose a certain type or color of drip edge to compliment the color pallet of their home and or roof. 


The most common choice due to its antioxidizing properties (resists rust) and color options.​
aluminium drip edge
galvanized steel drip edge

Galvanized Steel

A cheaper alternative to aluminium. It gets the job done, but is more prone to rusting over time.​


For the extra premium look! Copper can be such a beautiful accent to your home. It is costly, but it is beautiful.​
copper drip edge
gutter apron

Gutter apron

Gutter aprons are a unique style that diverts water directly into your gutter system instead of potentially leaking behind your gutters (causing rust and rot).​