Installation

Gutters for Sheds and Detached Garages in St. Louis

By St. Louis Gutter Service · November 8, 2026 · 8 min read

Plenty of alleys in south city share the same detail: a 1920s two-car brick garage, no gutters, and a strip of bare dirt trenched into the ground along the eave where decades of roof runoff have landed. The garage floor is damp at the back wall, the bottom course of brick is spalling, and the neighbor's fence post on that side is soft. Twenty-two feet of gutter would have prevented all of it.

Gutters for sheds and detached garages get skipped because the job feels too small to call anyone about. Here is what it typically costs, when it's worth doing, and how to get it done in one visit.

What gutters for sheds and garages cost

A detached garage needs 20–44 feet of gutter and one or two downspouts. At $9–$16 a foot that's $200–$700 of material and labor — less than the cost of getting a truck, a brake, a ladder and two people to your address. So almost every gutter company in the metro has a minimum, usually $350–$650. That isn't a markup on the garage; it's the floor for any visit.

Which means the sensible move is to bundle. If the house needs anything at all — a downspout upsized, a corner resealed, a run re-pitched, a cleaning — do the garage on the same visit and you pay for the gutter, not the trip.

Those are seamless aluminum numbers in .027 or .032 gauge. Sectional gutter from a big-box store is cheaper per foot and has a joint every ten feet, which on a 22-foot run means two leaks in five years.

Alley garage drainage: where the water goes

On a house you run the downspout out six feet and you're done. On an alley garage there often is no six feet, which is why alley garage drainage is the harder half of detached garage gutters. The options, in order of how well they work:

1. Discharge into the yard, away from both slabs. Best case. A hinged extension or a roll-out sleeve that you can lift for the mower.
2. Buried 4-inch line to a pop-up emitter in the yard. $12–$25 a foot to trench in St. Louis clay. Worth it when the garage sits tight to the alley and the only low ground is 20 feet away.
3. Splash block angled along the fence line. Cheap, imperfect, still far better than nothing.
4. A rain barrel off a garage. Garages are the right place for one — no basement to worry about, and the water is next to the tomatoes. See rain barrels and gutters.

Don't tie it into the sanitary sewer. Storm water in a sanitary lateral is generally not allowed in the MSD service area — check with MSD if you're unsure — and old alley garages sometimes have a mystery pipe that used to do exactly that. If yours has a stub in the floor of unknown destination, leave it alone and drain to daylight.

Slope and the neighbor

Alley lots in Dogtown, Tower Grove South and Bevo are narrow enough that a downspout on the wrong side dumps onto the property line. Two rules of thumb: never discharge toward a neighbor's foundation or garage slab, and never discharge across a shared alley apron where it will freeze in January. If the only low ground is toward the neighbor, run a buried line to a pop-up out front instead.

Details worth paying for on a small building

• Hidden hangers screwed into the rafter tails, not spikes. Detached garages usually have exposed rafter tails and no continuous fascia — a competent installer will fasten to the tails or add a nailer board.
• A 3x4 downspout even on a short run. The default small-roof downspout is a 2x3, but garage gutters clog faster than house gutters because they sit lower under the trees, and a 3x4 passes a wad of sycamore leaves that a 2x3 stops dead.
• A real end cap with sealant, not a crimp. On a 20-foot run the ends are where all the movement happens.
• Guards, sometimes. A garage under a silver maple gets seed-and-leaf load and nobody looks at it for years. Screen on a garage is a reasonable bet; on the house, be pickier — see gutter guards.

The fascia and rafter-tail check first

On anything built before 1950 with no gutter ever installed, the rafter tails have been rained on for a century. Some are fine — old-growth fir stays hard. Some are punky at the last two inches and won't hold a screw. A careful contractor checks that before quoting, because replacing six rafter tail ends is real carpentry and it changes the number. The same logic as fascia and soffit repair on a house.

When it isn't worth it

A shed with a metal roof, a gravel apron, and nothing within ten feet that water can hurt: skip the gutter, extend the gravel drip strip, spend the money on the house. Gutters are for protecting a foundation, a wall, or a doorway you walk through. If none of the three are in play, there's nothing to protect.

Getting a number

Take a photo of each side of the building and measure the eaves with a tape. That's usually enough for a contractor to give a rough range on the phone, confirmed once someone has been up the ladder. If the house needs work too, ask for one written quote covering both — house and outbuilding, separately priced, one trip. What a full gutter installation involves is on that page, and the ranges for everything else are on the cost page.

A checklist before you call

Five minutes in the yard makes the phone call shorter and the quote more accurate:

• Measure each eave that needs a gutter, in feet.
• Note the roof. Shingle, metal or rolled roofing, and roughly how steep.
• Find the low ground. Stand in the rain or after it and see where water already runs.
• Look at the tails. Exposed rafter tails or a fascia board? Any that look dark or soft?
• List the trees that hang over the building.
• Check the neighbor's side. How close is their fence, garage or foundation to your drip line?
• Add the house. Anything on the main house that needs attention, so both jobs can be quoted together.

Common mistakes on small buildings

• Draining toward the alley apron. It looks out of the way until it freezes into a sheet of ice in January.
• Skipping the end caps. A crimped end on a short run is where the first leak shows up.
• Undersized downspouts. A small roof still sheds a lot of water in a two-inch-an-hour storm, and garage gutters catch more leaves.
• Fastening to soft wood. Screws in punky rafter tails pull out with the first load of wet leaves.
• Forgetting it exists. A garage gutter nobody cleans is a gutter that overflows onto the same strip of dirt it was meant to protect. Add it to the house cleaning list.

Common questions

Does a shed need gutters?

Only if there is something nearby the runoff can hurt. A shed with a gravel apron and nothing within ten feet usually doesn't. If the drip line lands against a wall, a slab, a doorway or a neighbor's fence, a short gutter and one downspout are worth it.

How much do gutters for a detached garage cost?

A single-car garage with gutter on one side typically runs $350–$600 installed, and a two-car garage with both sides done $600–$1,100. Because most companies have a visit minimum, the cheapest way to get it done is on the same trip as any work on the house.

Where should a garage downspout drain on a city alley lot?

Into the yard and away from both slabs if you possibly can, with an extension you can lift for the mower. If the only low ground is toward a neighbor or across a shared alley apron, a buried line to a pop-up emitter out front is the better answer. Never tie it into a mystery pipe in the garage floor.

Can I put gutters on a shed myself?

On a small shed with a low eave, yes, if you are comfortable on a short ladder. Use a seamless or long single piece if you can, hidden hangers into solid wood, a sealed end cap and an extension at the bottom. On a two-car garage or anything with soft rafter tails, the visit minimum is often worth paying.