Half Round, Square Line, Deep Flow or Ogee: Which Guttering Do I Need?

What a Profile Is, and Why It Is Two Decisions at Once

Cut a gutter across and look at the end: that outline is the profile. It is usually discussed as a matter of taste, and taste is half of it, but the same outline also fixes the cross-sectional area of water the run can hold and the speed it moves at. Those two things are decided together whether you mean to decide them or not.

The second consequence is less obvious and causes more trouble. A profile is a system, not a shape. Its brackets, unions, stop ends, angles, running outlets and downpipe connectors are designed around that one section, and they seal by clipping over a formed edge at a particular distance from a particular curve. Change the profile and every fitting on the run changes with it.

So the question is never only "which looks right on my house". It is which shape suits the elevation, whether it carries what the roof above it sheds, and what is already there that any new work has to meet.

The Four Sections You Will Meet on Cheshire Houses

Half round is the plain semicircle, the default across older brick housing and the section most people picture when they think of a gutter. It is quiet against a wall, it suits a house with any period detail at all, and the common domestic size is nominally 112mm across the top, with a smaller size used on porches, garages and outbuildings. Of the four it holds the least for a given visual depth.

Square line has a flat front face and a squared back and came in with the estates of the 1970s and 1980s, where it still looks entirely at home. For a similar apparent depth it holds more than half round because the corners are filled rather than curved, and the flat face catches light in a way that reads as crisp on a modern elevation and slabby on a Victorian one.

Deep flow is a half round made deeper, and it exists for one reason: to put meaningfully more capacity into a run without changing the look much or asking for a bigger downpipe than the house can take. It is the usual answer where a roof is large, steep, or draining to a single outlet, and where a plain half round overshoots in heavy rain.

Ogee carries a moulded front face — the S-curve that copies the profile of Victorian cast iron — with a flat back that sits tight against the fascia. It is the section to use on an older frontage where half round looks thin, and it is the one usually available in a cast-iron effect finish. It also holds a good deal, because behind the decorative face it is essentially a deep box.

Capacity: Working Out Whether Yours Is Big Enough

What a run has to cope with is set by the roof area draining into it, the pitch of that roof, and how many outlets share the load. Area is the easy one. Pitch is the one people miss: a steep roof delivers water to the eaves faster than a shallow one of the same area, so it arrives in a shorter, heavier surge. Outlets matter most of all, because a run with an outlet at each end handles roughly twice what the same run handles draining to one corner.

The tell-tale of an undersized run is specific. It copes with ordinary rain and overshoots the front edge in a downpour, it overshoots along a length rather than at one point, and the gutter is clear when you look afterwards. That is capacity. A run that dribbles from one joint in all weathers is a seal; one that holds standing water and overflows at a single low spot is a fall or a bracket problem; one full of moss and grit is a blockage. Only the first of those is solved by a bigger section.

Extensions are the common cause. A rear extension that ties into the existing roof often puts extra square metres onto a run that was already at its limit, and nothing changes at the gutter because nobody thought about it. Conservatory roofs and porch roofs feeding into a main run do the same on a smaller scale.

Where capacity is short there are three fixes and only one of them involves a bigger gutter: move up a profile, add a second outlet and downpipe, or split the run so it drains both ways from a high point in the middle. Which is right depends on where a downpipe can sensibly go and what is at the bottom of it.

Why Two Makers’ 112mm Half Round Will Not Clip Together

This is the one that costs people money, and it is worth being precise about. A nominal size is a description of roughly how wide the section is across the top. It is not a standard that makes one maker’s section fit another’s, and there is no agreement between manufacturers that their sections should interchange. Two gutters can both be sold as 112mm half round and differ in the exact width, in the depth, in the thickness of the wall, and above all in the shape of the rolled bead along each edge.

The bead is what everything clips to. A union, a stop end, an angle and a running outlet all grip that bead and press a rubber seal against the inside face, so a few tenths of a millimetre of difference in its shape is the difference between a joint that seals and one that sits slightly open. Brackets have the same problem from the other side: they are cut to hold a specific curve at a specific spacing.

The result is that mixing systems produces a joint that looks fine on the day and weeps within a year or two, usually after somebody has filled it with sealant to stop it. Sealant is the visible sign of a hybrid joint and it is the first place to look on a gutter that has been "repaired" twice.

Downpipes repeat the problem. Round pipe and square pipe are different diameters and different systems, and the running outlet ties the gutter you choose to the pipe you can connect to it. Add to that the sections fitted on estates in the 1970s that no longer have a current equivalent at all, and the practical rule is simple: match the system if it is still made, and otherwise replace an elevation complete to a natural break — a corner, a party wall, a stop end — rather than splicing new to old halfway along.

Identifying What You Already Have, From the Ground

Stand at one end of the house and look along the run at the stop end, or at the point where the gutter meets the downpipe. A semicircle is half round. A flat front with square corners is square line. A front face with a moulded curve in it, deeper than it is wide, is ogee. Deep flow reads as half round until you compare it with a neighbour's and notice it sits lower below the fascia.

A phone camera zoomed in on the end of a run, taken from the garden, is usually enough for anyone to identify the profile, and photographs of the stop end, the outlet and the downpipe together will settle nearly any case. That is the whole check. Please do not go up a ladder to measure anything: there is nothing at eaves height that a photograph will not tell us.

It is also worth remembering that the gutter and the boards are separate choices. Black or anthracite gutter above white fascias is the pairing most often fitted around here, and a dark run against a pale board tends to define the roof edge and hide the joints. Cast-iron effect ogee earns its place on an older frontage. What none of those colours change is capacity, which is decided entirely by the shape.