Types of gutter: which one your roof has, and what goes wrong with each
A gutter is named for where it sits on the roof, and then for its shape. The eaves gutter runs along the edge. The valley gutter runs up the corner where two slopes meet. The box gutter sits in the trough between two roofs. The inside gutter hides behind a parapet. Each one collects a different share of the rain, blocks in its own way, and floods a different part of the house when it does.
All of them end at a downspout, and everything from the bottom of the downspout to the canal is drainage, which is part of our outdoor plumbing service. The gutter itself is roof work. This page tells you which kind you are looking at and who to send for.
Where each type sits
Stand across the street and look at the roofline. If you can see the gutter, it is an eaves gutter. If the roof has an inside corner, there is a valley gutter under the sheets there whether you can see it or not. If two roofs meet in a trough, or a lower roof runs into a wall, there is a box gutter in that trough. If the roof edge is a flat wall with no gutter showing, the gutter is behind it.
Drag the drawing sideways to see all of it.
Eaves gutter, the ordinary alulod: box type and Spanish type
The gutter along the roof edge is the one most houses have and the one Filipino calls the alulod. In a hardware shop it is sold by its profile: box type, which is a plain rectangular channel, or Spanish type, which is the same channel with a curved, stepped front for the look of it. Both are bent from pre-painted G.I. sheet, and stainless versions exist for the same shapes. The 18 inch in a listing is the width of the flat sheet before it is bent, not the width of the channel.
Drag the drawing sideways to see all of it.
What goes wrong with it
Leaves and dirt at the outlet, so the channel fills and spills over its front edge along the whole length. A sag between two hangers, so water stands in the middle and the sheet rusts from the inside out at the low point. A joint that opened when the sealant aged, which shows as one steady drip at one spot. And a gutter that was never given enough fall toward its outlet, which overflows in a typhoon no matter how clean it is.
What to do about it
Clear the outlet before the rains and again after the first big storm. A wire strainer over the outlet keeps most of it out. Anything beyond that, resealing a joint, re-hanging a sagging length, adding a second downspout to a long run, is a roofer or tinsmith job. If the water comes out of the downspout fine and then floods the yard, that end is ours; our guide to the alulod and downspout covers what should happen at the bottom.
PVC gutter
A PVC gutter is the same job done in plastic: a half-round or square channel sold in lengths, with its own elbows, end caps, outlets and brackets that clip the pieces together. It never rusts, it is light enough for one person to hang, and it suits a small roof, a carport, a laundry extension or a rainwater collecting setup.
Where it falls short
Plastic softens in years of sun and sags between brackets that are too far apart, so the water stops running toward the outlet. It does not take a ladder leaning on it. The joints are clipped and gasketed rather than sealed, and a gasket that has dried out leaks at every joint at once. On a long main roof in a typhoon area, most builders here still bend the gutter from G.I. sheet and use PVC for the downspout, where it does its best work.
Valley gutter
Wherever a roof turns a corner inward, two slopes meet in a line that runs from the eave up to the ridge. That line is the valley, and the rain from both slopes runs down it. A valley gutter is the V-shaped sheet laid along that line under the roofing sheets, wide enough that the sheets stop short of its bottom and the water runs in the metal rather than between the sheets. You cannot see it from the ground. You find out it exists when it fails.
What goes wrong with it
It carries more water than any other gutter on the roof, in a channel that leaves and twigs settle into because they have nowhere else to go. When it blocks, the water backs up under the roofing sheets on both sides and comes through the ceiling well away from any wall, which looks like a hole in the roof. If the sheets were cut too close to the bottom of the V, or the V was made too narrow for the two slopes feeding it, the same thing happens in heavy rain without any blockage at all.
What to do about it
Clear it from above before the rains, with care, because the sheets on either side are not meant to be walked on at the edge. A leak at a valley is a roofer's job and usually means lifting sheets. If the stain inside is away from every wall and worse in long rain, read our guide to water leaking from the ceiling before you send for anyone.
Box gutter in a trough
The box type gutter on the shelf and the box gutter on a plan share a name and not much else. On a plan, a box gutter is the wide, flat-bottomed channel set in a trough: where two roofs slope toward each other, where a lower roof runs into the wall of a higher one, or along the edge of a flat roof. The water in it cannot spill over an edge the way an eaves gutter spills, because both sides are roof or wall. It has to leave through its outlets or it rises.
What goes wrong with it
Rising water. A box gutter with a blocked outlet fills until it reaches the edge of the roofing sheets on either side and then runs under them. It is also the gutter most likely to have been made too shallow or with too few outlets for the two roofs feeding it, because it was sized by eye. Rust at the seams, where it was soldered or riveted in short lengths, is the other failure.
What to do about it
Give it an overflow: a second outlet or a notch at the end, so a blocked outlet spills somewhere harmless rather than into the ceiling. Keep the outlets strained and clear. Resizing or resealing one is roof work.
Inside gutter, behind a parapet
Many newer houses here are built with a parapet, a low wall that continues the outside wall up past the roof so the roof edge looks flat and modern. The rain still has to be caught, so the gutter sits behind that wall, between the end of the roofing sheets and the parapet. That is the inside gutter. Its outer side is the wall itself. From the street there is no gutter to see, which is the point of it.
What goes wrong with it
It is the gutter that floods the house. An eaves gutter that blocks spills onto the ground. An inside gutter that blocks has nowhere to spill but under the roofing sheets and down the inside of the wall, which is why "inside gutter repair" is the job roofers here advertise most. It is also hard to reach, so it is cleared least, and the flashing where the gutter meets the parapet is the joint that fails.
What to do about it
Treat the outlets as the whole system. More of them than you think you need, each with a strainer, and an overflow pipe through the parapet set a little above the normal water level, so a blocked outlet shows as water spouting from the wall rather than a stain on the ceiling. Clear it every time the eaves gutters are cleared. Anything structural is a roofer's job.
The two that are not roof gutters
A wire gutter is an electrical fitting: a metal trough that carries wiring between panels, sold by electrical suppliers as a wireway or a breaker gutter. A road gutter is the concrete channel at the edge of a street, beside the kerb. Neither has anything to do with your roof, and if you searched for either, you want an electrician or the municipal engineer rather than this page.
Where the water goes next
Whatever the type, every gutter ends in a downspout, and the downspout has to empty somewhere. Into a catch basin and on to the canal is right. Onto the ground against the wall is slow damage. Into the septic tank or the house drain is wrong: the Revised National Plumbing Code of the Philippines does not allow rain into a line meant for sewage, and every storm then fills the tank. That half is plumbing, and it is the half we do. Our guides to the alulod and downspout and the backwater valve cover what happens when it is done wrong, and the plumbing code page says where the rule comes from.
Questions about gutter types
- What are the types of gutter on a house?
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By where they sit: the eaves gutter along the roof edge, the valley gutter where two slopes meet, the box gutter in the trough between two roofs, and the inside gutter behind a parapet. By shape and material: box type, Spanish type, half-round, in G.I. sheet, stainless or PVC.
- What is a valley gutter?
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The V-shaped sheet laid in the inside corner where two roof slopes meet, under the roofing sheets. All the rain from both slopes runs down it. It is also the name of a concrete channel across a road, which is why some search results are about pavements.
- What is a box gutter?
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Two things. In a hardware shop, a box type gutter is the ordinary rectangular G.I. gutter hung on the fascia. On a roof plan, a box gutter is a wide rectangular channel set in the trough between two roofs or between a roof and a wall, where water cannot simply spill over an edge.
- What is an inside gutter?
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A gutter hidden behind a parapet wall, so the roof edge looks flat from the street. The water has nowhere to overflow except inward, into the house, which is why an inside gutter needs its outlets kept clear more than any other kind.
- Is a PVC gutter good for a house in the Philippines?
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For a small roof, a carport or an extension it does the job and does not rust. It softens in the sun over the years, it needs brackets close together so it does not sag between them, and it will not take a ladder leaning on it. A long main roof in a typhoon area is usually done in G.I. sheet.
- What is a wire gutter?
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An electrical fitting, not a roof part: a metal trough that carries wiring between panels, also called a wireway or a breaker gutter. If you searched for it, you want an electrician and an electrical supplier, not this page.
- Who installs a gutter, a plumber or a roofer?
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The gutter and the flashing on the roof are a roofer or tinsmith job. The downspout at ground level, the catch basin and the pipe out to the canal are drainage, which is a plumbing job and part of our outdoor plumbing service.
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The gutter is roof work. The downspout is ours.
Catch basins, downspout pipes and the drain out to the canal are part of our outdoor plumbing service. Send us the problem and say where the water ends up.
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