Examination no. 03 / the hood family
Reverse Curve and Surface Tension Guards
The only guard family that does not use a screen at all. It works by persuading water to turn a corner, and it stops working at exactly the moment you most need it to.
How it is supposed to work
A reverse curve guard is a solid hood. It covers the whole mouth of the gutter and curls back on itself at the front, leaving a narrow slot along the nose. There is no mesh and nothing to blind.
The mechanism is adhesion. Water running off the shingle meets the curve of the nose and, because water clings to a surface it is already wet, a thin sheet of it follows that curve round and back into the slot instead of leaving the edge in a straight line. Leaves, twigs and seed have no such attraction to the metal, so they carry on in the direction they were already travelling and fall off the front.
When the conditions suit it, that is a genuinely elegant piece of engineering, and it does something no screen can do: it never blinds, because there is nothing fine to block.
What you will be told
There is no screen, so there is nothing to clog. It cannot fail.What happens on the roof
The first half is true. The second does not follow from it. A reverse curve guard does not fail by clogging, it fails by capacity, and capacity is a harder failure to see.
The amount of water the nose can turn is finite. Exceed it and the excess does not queue politely, it leaves the nose in a straight line and lands in front of the house. The gutter behind the hood is clean, dry and completely uninvolved.
So it is not clog free versus clog prone. It is one failure mode traded for another, and the one you are trading into arrives during the heaviest rain of the year.
Why a St. Louis roof is a hard test
Three conditions decide whether the nose can cope, and this region supplies all three at once in spring.
A homeowner who tests a reverse curve product in ordinary rain will be delighted with it. The problem announces itself once, in April or May, with water sheeting off the front of the house onto the flowerbed while the gutter behind it stays dry.
The things nobody mentions in the driveway
- It is visible. A reverse curve hood sits proud of the fascia and reads as a band of metal along the roof edge. On some houses that is invisible. On a house with a deliberate roof line it is the first thing you see. Look at one from the pavement, in daylight, before agreeing to it.
- The slot is not maintenance free either. Grit and shingle dust build up inside the nose over years, and the slot narrows. Getting into it means removing the hood, which is not a ladder and a brush job.
- Debris still lands somewhere. Everything that slides off the front ends up in the bed below the eave. That is not a fault, it is the design, but people are surprised by it.
- It genuinely never blinds. On a roof shedding heavy grit, where a fine mesh would be loaded within a season, this is a real and specific advantage. See the roof age page for when that matters most.
Who it is right for
A moderate pitch, a run that is not collecting an enormous plane, an older roof that is shedding grit, and an owner who has looked at the product on somebody else's house first. Under those conditions a reverse curve guard is a sound purchase and will outlast a mesh.
On a steep roof, under a valley, or on any run that already overflows in heavy rain because the outlet cannot empty it fast enough, a hood makes the existing problem harder to diagnose rather than better. Fix the throughput first: what has to be right underneath.
Surface tension guards
If water is going over the front, say when
Reverse curve guards usually behave perfectly in ordinary rain and fail in the heaviest ten minutes of the year. That timing is the diagnosis, so it is worth telling us.
Keys Roofing will look at the roof pitch above the run before recommending anything with a nose on it.
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