Installation

K Style Gutters vs. Half-Round: Which Fits Your House

By San Antonio Gutter Pros · November 3, 2026 · 8 min read

Stand on Broadway in Alamo Heights and look at the rooflines. The 1920s Tudors and Spanish revivals carry half-round gutters, tubes cut lengthwise and hung on brackets. Drive twenty minutes north to Stone Oak and nearly every house has K style gutters, the flat-backed profile with the little ogee curve on the front that looks like crown molding. Neither is wrong. They're two different answers to two different houses, and picking the wrong one for yours costs either money or the way the house looks.

K style gutters and half-round: what each shape actually is

K-style is the profile on roughly nine of every ten houses built after 1960. The back is flat and screws straight to the fascia, the bottom is flat, and the front face has the decorative step. K style aluminum gutters are formed seamless on the truck from coil in 5- and 6-inch widths. Because the trough is squarish, it holds more water per inch of width than a half-round, and because the back is flat, it hangs on hidden hangers that clip inside, out of sight.

Half-round is a half-circle. It's the original gutter shape, it's what copper is usually formed in, and it's what the pre-war houses in Monte Vista, Olmos Park and the old part of Boerne were built with. It hangs on brackets, either roof-mounted straps or fascia brackets that show below the gutter, and those brackets are part of the look. The smooth interior doesn't have the inside corners where debris packs, so it self-cleans a little better under a live oak.

Capacity, since that's what a storm cares about

A 5-inch K-style holds about 1.2 gallons per running foot. A 5-inch half-round holds closer to 0.8. To match a 5-inch K-style you need a 6-inch half-round, and to match a 6-inch K-style you're into 7-inch half-round, which is a special-order item at a special-order price.

That matters here more than in a drizzle climate. San Antonio's rain shows up as an inch or two an hour a handful of times a year, and the gutter has to survive the worst fifteen minutes. On a 1928 house with a modest gable roof, 6-inch half-round handles it. On a steep 3,200-square-foot roof in Fair Oaks Ranch, half-round would need to be 7-inch with 4-inch round downspouts, and at that point K-style in 6-inch with 3x4 downspouts is the better engineering and a third of the price.

Side by side

Fitting the house

The test is simple: does the house have a fascia board? Post-war houses have a flat vertical board at the roof edge, and K-style screws to it. A lot of pre-war houses here have exposed rafter tails or a crown molding at the eave instead, and there's nothing flat to screw a K-style to. Half-round on roof straps or on fascia brackets that stand the gutter off the molding is the correct install, and forcing K-style on with shims looks like exactly what it is.

On a Spanish revival with a clay tile roof and stucco walls, half-round copper or half-round aluminum in a bronze finish is the only thing that doesn't fight the house. On a 1970s ranch in Leon Valley or a 2008 two-story in Cibolo, K-style in the trim color disappears, which is the goal. Half-round on those houses reads as a costume.

There's a middle case. The 1940s and 50s cottages around Woodlawn Lake and in Jefferson often have a small fascia and a low-pitched roof, and either shape works. Most contractors suggest a 5-inch K style gutter there because the roofs are small, the price is lower, and the hangers are hidden.

Half round gutters in San Antonio are concentrated in a handful of older neighborhoods: Alamo Heights, Terrell Hills, Olmos Park and Monte Vista, plus scattered pre-war houses downtown and in old Boerne. If your street is one of those, a neighbor's house is the best sample you'll get of what the profile looks like on your style of home.

Downspouts follow the gutter

K-style takes rectangular downspouts, 2x3 or 3x4. Half-round takes round ones, 3-inch or 4-inch, and the outlets, elbows and brackets are all different parts. Mixing them, a round downspout on a K-style outlet with an adapter, is a common shortcut on repair jobs and the adapter is where it leaks. If you're replacing one run of half-round on an Alamo Heights house and keeping the rest, match it. The Alamo Heights page goes into the copper-and-half-round repair work those streets need.

Cost, honestly

Half round aluminum gutters in San Antonio run $14–$22 a foot installed, against $9–$14 for K-style, because the brackets cost more, they're set one at a time, and most crews install far more K-style than half-round. On a 160-foot house that's roughly $1,500 versus $2,600. Copper half-round is another world, $35–$55 a foot, and it's worth it exactly once: on a house where the original copper is already there and you're extending or repairing it. The full price tables are on the cost page.

What to ask half round gutter installers

Fewer crews here hang half-round regularly, so a few questions sort out who has done it before:

• Which brackets will they use, fascia brackets or roof straps, and at what spacing? Visible brackets are part of the look, so ask to see one.
• Are the downspouts round, with matching round outlets and elbows, or is it an adapter onto a rectangular pipe?
• For copper, are the seams soldered or only sealed? Soldered is the traditional detail.
• Have they hung half-round on a house with exposed rafter tails or a tile overhang, and how did they set the pitch?

A quote that can't answer those in writing is a K-style quote with a different picture on it.

Common mistakes when choosing a profile

• Choosing by photo instead of by roof. Half-round looks good in a catalog, but a 5-inch half-round under a large steep roof overflows in the first heavy storm.
• Forcing K-style onto eave molding. Shims and spacers behind a flat-backed gutter look patched from the street and leave gaps where water runs behind.
• Mixing round and rectangular parts. An adapter between a round downspout and a K-style outlet is the first place a new system leaks.
• Matching only the gutter. If you replace one run of half-round, match the brackets and downspouts too, or the repair stands out from the rest of the house.
• Ignoring the downspout count. Either profile needs enough downspouts for the roof area feeding it; a bigger gutter can't make up for one outlet on a long run.

A short recommendation by house

• Built after 1960, flat fascia: 5- or 6-inch K-style, sized to the roof.
• Pre-war with exposed rafter tails or eave molding: 6-inch half-round aluminum on fascia brackets, or copper if the house already has it.
• Tile roof, stucco, Spanish revival: half-round, hung on brackets that clear the tile overhang.
• Big steep roof, any age: K-style 6-inch, because half-round can't be sized for it without special order.

Material is a separate decision from shape; the gutter materials guide covers that. And whichever profile you pick, gutter installation here starts with a roof-area measurement, not a catalog page.

Common questions

Do half-round gutters hold less water?

Yes, at the same width. A 5-inch half-round holds roughly 0.8 gallons per foot against about 1.2 for a 5-inch K-style. To carry the same storm you generally go one size up in half-round, which is why 6-inch is the usual half-round size on a San Antonio house.

Are half-round gutters more expensive?

Usually. Typical installed ranges here are $14–$22 a foot for half-round aluminum against $9–$14 for K-style, because the brackets cost more and take longer to set. Copper half-round is a separate tier at $35–$55 a foot.

Which San Antonio homes suit half-round gutters?

Pre-war houses with exposed rafter tails or eave molding instead of a flat fascia board, Spanish revival homes with clay tile and stucco, and any house that already has original copper half-round. Most homes built after 1960 have a flat fascia and look right with K-style in the trim color.