Garage Roof Drip Edge: Why Water Runs Down the Walls

Water on a roof does not always fall off cleanly. It clings to the underside of the edge by surface tension and runs back toward the wall. A drip edge breaks that pull. It is a trim with a small lip, tucked under the covering and projecting past the fascia, the board that closes the bottom of the rafters. Water leaves the lip and drops clear.

Where does it sit on a garage?

On a flat garage roof the metal edge trim is fixed to the deck, the covering is dressed over its top, and the lip hangs over the gutter. On a sheeted garage the sheet itself overhangs the gutter by a set amount. In both cases the water must land in the gutter, not on the wall behind it or the ground beside it.

Without a drip detail, or with a trim that is bent, short or fixed at the wrong angle, water finds the quickest way back under the covering and soaks the deck. The first symptom is staining on the wall below. The second, a few seasons later, is rot in the edge board.

Our page on a leaking garage roof explains how to tell an edge problem from a roof problem.

A few minutes outside the garage during a downpour will show you the pattern. Water coming over the edge in a sheet and missing the gutter points to a trim that is too short. Water running along the underside of the fascia, then down the wall, points to a missing or flattened lip.

Could the gutter be the cause?

Often. A gutter set too high, so its back edge sits above the roof edge, catches nothing, and the water shoots over the top. A gutter that is too low and too far out misses it from the other side. A gutter full of leaves and silt overflows at the front or, worse, behind. Sagging brackets leave pools that spill over.

Another cause is the covering itself. On felt roofs, the felt is sometimes dressed over the edge board with no trim, and over time it curls up and lets water run behind. On sheet roofs, the sheet can be cut short during fitting. Garages with no gutter at all rely on the drip alone, and the ground below takes the splash.

Each of these fixes is different, so the survey finds which one is yours before a price is given.

It makes sense to renew edge parts together. A new trim on an old rotten fascia has nothing sound to fix to. A new gutter hung from a loose board will droop again. So we check the fascia for rot, replace sections that are soft and then fit the drip trim, the covering and the gutter as one set of details.

What goes wrong with a quick patch?

Sealant squeezed along an edge looks like a repair, but it only masks the gap. As the sealant shrinks and cracks, water returns. Metal flashings nailed through the face rather than fixed under the covering leave holes of their own. A proper job keeps the edge falling toward the gutter and lets water move off the roof without help from mastic.

Gutter size and fall matter. Brett Martin advises 1mm of fall for every 600mm of gutter, and our garage roof guttering page covers outlets, brackets and downpipes. A new run of gutter is a modest job compared with renewing a roof, and the survey sets the price for yours.

Pick a dry day and look from the ground. Check whether the roof edge overhangs the gutter, whether the gutter is straight, and whether dark, damp patches or green growth mark the wall below it. In rain, look for water that misses the gutter. Photos from the ground save a roofer time when you describe the fault.

What should a roofer tell you about the edge?

They should say what the edge is made of, where the water goes and what will change. Ask whether the trim is going to be replaced or reused, and whether the fascia is sound. Ask who will arrange access, since a garage beside a boundary can make ladders awkward. For a roof with plenty of rot, ask to see the damaged boards.

Our garage roof deck replacement page covers what lies under the covering at the edge, and the garage and asbestos roofs page sets out the wider service. Every edge we fit is checked against the slope, so water leaves into the gutter and away from your wall. You see a close photo of your own edge before agreeing the work.