Half-Round Gutters on an Older St. Louis House, and Why the Downspout Decides It

Plenty of older St. Louis houses, especially brick bungalows and early twentieth century two-story homes in the city and inner suburbs, were built with half-round gutters. They suit the house, and they are not a like-for-like swap for the K-style profile that most shops quote by default. Before anyone orders material, the existing run needs a measured look: its width, its outlet size, how it hangs from the fascia, and whether the downspouts are round or rectangular. Those four facts decide whether you can keep the look without giving up water capacity.

Gutters and guards

A half-round gutter is a semicircular trough. Its cross section is different from a K-style profile of the same nominal width, and that changes how much water it carries before the flow backs up at the low spots. Manufacturers publish capacity tables for each profile and size, and those tables should be the source for any downspout count. Do not assume a 5 inch half-round holds what a 5 inch K-style holds. Ask the installer to show the table for the exact profile on the order.

The downspout is where half-round runs most often go wrong. Round downspouts are the usual companion for a half-round trough, because the outlet at the bottom of the gutter is round and the downspout has to seat into it. A rectangular downspout fitted to a round outlet leaks at the joint, and a round downspout forced into a rectangular outlet does the same. If the house has an existing round downspout, measure its diameter at the collar before the new gutter is ordered, not after the old one is off the wall.

Hanging a half-round gutter needs a different method than a K-style hanger. Most half-round runs use strap hangers or spike and ferrule hangers rather than the clip that snaps onto a K-style profile. On brick, the fasteners need to go into the wood fascia behind the mortar joint, not into the brick face, and a run on a brick wall with soft mortar may need a fresh fascia board before it takes new hangers. Check the fascia for rot before the old gutter comes off, because the old hangers are often the only thing that has been holding the board in place.

Gutter guards on half-round are possible, but the fit is narrower. Some guard products are sized for K-style and some are sold for half-round, and a guard sized for the wrong profile will sit with a gap at the back where the trough meets the fascia. Leaves and needles collect in that gap. If you are weighing a guard, read the sales sheet for the profile it names, and ask what the product does with a half-round trough specifically. No guard makes the trough maintenance free, and a half-round trough already holding fine silt needs a clean-out before the guard goes on.

Mixed profiles on one house are a common result of partial replacement. A front run in half-round and a side run in K-style will not drain the same way, and the joints where the two meet need their own detail. If the house has both, ask for the transition to be drawn on the written scope with the outlet locations marked.

What it costs

Half-round work usually prices differently from K-style because the material, the hangers, the outlets and the labor on the run are all different. Expect the quote to carry separate lines for the trough, the outlets, the hangers, the downspouts, the end caps and the removal of the old system. A single lump sum for the run hides the parts that matter, so ask for the line items.

Watch for the cost of the fascia. If the board behind the old gutter has soft spots, replacing it is a separate line, and it is worth asking whether the price includes paint or only the bare board. Repairing one board is a small job, but a run with rot along most of its length can change the whole project, and the difference should appear on the quote before you sign, not on the day the old hangers come off.

Access adds cost on older houses. A two-story run on a narrow side yard, a run with a porch roof in the way, or a run that has to be lifted over a brick ledge all take more time. The quote should say how the crew will reach the run and whether a ladder or lift is included. The same question applies to a repair: a single section replaced on a half-round run still needs the matching profile, and a mismatch is harder to fix later than it is to order right the first time.

Material choice moves the number too. Aluminum is the usual choice for a half-round trough on an older house because it is light and does not corrode the way steel does, but copper is used on some period houses and costs more. The quote should name the material and the thickness, so you can compare like with like across bids.

What to ask

These are the questions that show whether a half-round quote is written for your house or for a generic gutter run.

• Which profile and nominal size is on the quote, and what does the manufacturer's capacity table say about the downspout count you were given?
• Are the downspouts round or rectangular, and do the outlets match the downspouts at the collar?
• How is each hanger fastened, and into what? On brick, is the fastener going into the fascia behind the mortar?
• Has the fascia been checked for rot with the old gutter off, and is any board replacement priced separately?
• If a guard is quoted, is it sized for half-round, and does the quote show how the back edge seals to the fascia?
• Where does a mixed profile meet, if the house has both, and is that joint drawn on the scope?
• What material and thickness are named, and does the quote state the aluminum gauge?

Keep a copy of the scope and photos of the existing run before the crew starts. When the new gutter is up, photos of the outlet, the hanger heads and the fascia at each end show exactly what was installed. If the run looks wrong after the first hard rain, call the Seamless Gutters STL office at (314) 220-2333 and ask for the written scope, then compare it to what is on the wall.