What a Drip Edge Does, and What Happens Without One

A drip edge is a bent strip of metal that runs along the bottom edge of the roof and up the gable ends. Most homeowners have never heard the term, and most quotes barely mention it. It is also one of the cheapest parts of a roof to get right and one of the more expensive to get wrong, because the damage it prevents happens to wood you cannot see.

What it is actually doing

Water running down a roof does not want to fall straight off the edge. Surface tension pulls it back under the roofing and onto whatever is behind it, which is the fascia board and the edge of the decking. A drip edge gives the water a hard metal lip to break from, so it drops into the gutter instead of wicking back.

It does two other jobs. It holds the edge of the underlayment down so wind cannot lift it, and it covers the cut end of the deck, which is end-grain wood and soaks up water faster than any other part of the roof.

How it is supposed to be layered

This is where I see it done wrong most often. At the eave, the drip edge goes on the deck first and the underlayment laps over it, so any water that gets under the roofing runs out on top of the metal. At the rake, the gable end, it goes over the underlayment, because there the job is keeping wind-driven rain from getting under the edge.

Put it the wrong way at the eave and you have built a funnel. Water that reaches the underlayment runs down, hits the back of the drip edge, and goes into the fascia. The roof will look fine from the ground for years while the wood behind it rots.

What goes wrong without it

• Fascia rot. The most common result. A homeowner notices it when the gutter starts sagging because the wood it is screwed to has gone soft.
• Deck edge rot. The first foot of plywood at the eave is where ice-dam water sits in a Midwest winter. Without a drip edge covering that edge, it drinks.
• Staining and dripping behind the gutter. Water that should be in the gutter runs down the fascia instead. On a white house you see it. On a dark one you find it later.
• Wind lift. A bare underlayment edge is a handle for the wind.

None of those show up the first year. They show up at year eight or ten, which is why an old post on this site promised a drip edge would "add five years" to a roof. I am not going to put a number on it. I will say that on tear-offs, the houses with rotten eave decking are very often the houses where the drip edge was missing or buried under the felt.

How it works on a metal roof

On a metal roof, the drip edge is usually part of the eave trim, and the panel is hemmed over it or locked onto it. That hem matters. A standing seam panel that hooks over the eave trim is held at its most exposed edge by metal, not by a fastener, and that is a big part of why those roofs hold in wind. The gable trim does the same job at the rake. Color-matched trim is standard, so this is not a place where anything is visible unless you go looking.

Where it is not the problem

I want to be honest about the limit. A drip edge will not fix a roof that is leaking at a valley, a chimney, or a sidewall. It is an edge detail. If your fascia is rotting from the top down, look at the drip edge. If water is showing up on a ceiling in the middle of the house, look elsewhere.

And if your roof has one, laid the right way, there is nothing to do. It is not a maintenance item. It is metal under metal.

What to look for in a quote

A roof quote should say that drip edge is included at eaves and rakes and what it is made of. If a quote for a metal roof does not mention eave or gable trim at all, the roof has not been detailed, only priced. That is worth asking about before you sign.

Now you have the context to know what that small strip of metal is worth.