How much slope should a gutter have?

About 1/4 inch of fall per 10 feet of run, pitched toward the downspout. That is enough to drain fully without standing water and shallow enough that the gutter still looks level from the ground. On runs longer than roughly 40 feet, crown the high point in the middle and slope in both directions to a downspout at each end rather than trying to carry one long fall — a single 60-foot run at consistent pitch would drop an obviously visible inch and a half.

How far apart should gutter hangers be?

Twenty-four inches on center is the residential standard, tightened to about 16 inches in snow country where ice loading is what pulls gutters off a house. Drive hanger screws into the rafter tails behind the fascia wherever you can find them rather than relying on the fascia board alone. Hangers are inexpensive; re-hanging a sagging run in two years is not.

How many downspouts do I need?

Plan one downspout per 30 to 40 feet of gutter run, with the low end of each run draining to one. Use the low end of that range — closer to 30 feet — in high-rainfall regions or under a large or steep roof that concentrates a lot of water into the gutter quickly. Inside corners and long runs both want their own downspout. Under-draining a run causes overflow at the worst moment, during the heaviest rain.

Which way do gutter and downspout joints overlap?

Always so water runs over the seam, never into it. On the gutter, the upstream section goes inside the downstream one so flow passes across the lap. On the downspout, each upper section fits inside the one below so water stays in the pipe rather than leaking out at every joint. Getting this backwards is one of the most common DIY gutter mistakes and produces a run that drips at every seam.

How far should a downspout discharge from the house?

At least 4 to 6 feet from the foundation, further on clay soils or where the grade falls back toward the house. A gutter system that is perfectly installed but dumps at the footing has simply concentrated the entire roof's water into one spot against your foundation, which is worse than no gutter at all. Use splash blocks, downspout extensions, or tie into a buried drain line that daylights well away from the building.

How to Install Gutters — Step-by-Step Guide

An eight-step guide covering downspout planning, fascia repair, the slope layout and chalk line, hanger spacing, cutting outlets, joining sections so seams shed water, and testing the finished run with a hose.

Gutters look like the simplest thing on a house and quietly cause some of the most expensive damage when they're wrong. Almost every failure traces back to one of three things: not enough slope (standing water, then ice, then a torn-off run), seams lapped backwards (a run that drips at every joint), or a downspout discharging at the foundation (which concentrates the entire roof's water exactly where you least want it). Get the linear feet, downspout count, and hanger count first with the Gutter Calculator, then work through the steps below.

Tools & Materials

Tools: an extension ladder with a stabilizer (a standoff keeps the ladder off the gutter you are trying to hang), a chalk line and a long level, aviation snips, a cordless drill with a hex driver, a downspout outlet punch or hole saw, a pop rivet gun, and a caulk gun. A garden hose is the final and most important tool — it is the only honest test of the finished run.

Materials (count them with the calculator below):

Gutter in 10 ft sections, hidden hangers, drop outlets, downspouts, and elbows — all counted by the Gutter Calculator
End caps — two per separate run, which is the input people most often get wrong
Gutter sealant and pop rivets for every joint
Splash blocks or downspout extensions for the discharge

Step 1: Measure the Eave and Plan Downspouts

Measure every eave that needs gutter, and count separate runs — each run needs two end caps, so a house with four disconnected runs needs eight. Plan one downspout per 30–40 feet of run, at the low end and at inside corners, discharging where water can actually leave. Downspout placement determines which way everything slopes, so settle it before a single hanger goes up.

Step 2: Inspect and Repair the Fascia First

The entire system hangs off the fascia, so anything soft gets replaced before you mount hardware. Probe with an awl, concentrating where the old gutters leaked — that is exactly where rot hides. Hanging new gutter on failing fascia buys you a sagging run and a second, bigger repair in a couple of years.

Step 3: Mark the Slope and Snap a Chalk Line

Set the high end about 1 inch below the roof line so runoff can't overshoot, then calculate the drop at roughly 1/4 inch per 10 feet, mark the low end, and snap a chalk line. On runs over about 40 feet, crown the middle and slope both ways to a downspout at each end — a single 60-foot fall would drop an inch and a half and look visibly crooked from the driveway.

Step 4: Mount Hangers 24 Inches On Center

Fasten hidden hangers along the chalk line every 24 inches, driving screws into the rafter tails behind the fascia wherever you can hit them. Tighten to 16 inches in snow country — ice loading, not water, is what rips gutters off houses. The calculator's hanger spacing input handles this: dropping from 24 to 16 inches on a 160-foot system takes the hanger count from 80 to 120.

Step 5: Cut and Seal the Downspout Outlets

Mark and cut each outlet on the ground, before the section goes up — it is far easier and far more accurate than working overhead on a ladder. Punch or hole-saw the opening, fit the drop outlet, and seal around it from inside the gutter. Sealant belongs on the wet side, where water pressure pushes it into the joint rather than peeling it off.

Step 6: Hang the Gutter and Join the Sections

Set the gutter into the hangers along the chalk line, working from the high end down. The critical detail: lap the upstream section inside the downstream one so water runs over the seam instead of into it. Rivet and seal every joint and every end cap, from the inside. Seams are where gutters leak, and sealant is cheap relative to getting the ladder back out.

Step 7: Install Downspouts with Three Elbows Each

A typical downspout takes about three elbows: two to offset from the drop outlet back to the wall, and one kick-out at the bottom. Strap the downspout to the wall at least every 10 feet or once per story. Assemble it so each upper section fits inside the lower one — the same over-not-into logic as the gutter seams, and just as commonly reversed.

Step 8: Test with a Hose and Extend the Discharge

Run a hose into the high end of every run and watch. Water should reach the downspout with no standing puddles and no drips at the seams. Adjust hangers to fix any low spot now, while the ladder is still up. Then carry discharge 4–6 feet from the foundation with splash blocks, extensions, or a buried line that daylights well away. A flawless gutter dumping at the footing has just concentrated your whole roof into one spot against the foundation — genuinely worse than having no gutter there at all.

Common Mistakes

Too little slope (or none). Standing water breeds mosquitoes, freezes into destructive ice, and adds weight that pulls the run off the fascia.
Seams lapped backwards. Upstream goes inside downstream, on both gutter and downspout. Reversed laps drip at every joint forever.
Too few downspouts. One per 30–40 ft. Under-draining shows up only in the heaviest rain, which is exactly when overflow does damage.
Hanging on rotten fascia. Fix the wood first. The gutter is only as sound as what it is screwed to.
Discharging at the foundation. The single most damaging mistake, and the cheapest to fix — an extension costs a few dollars.

Cost: DIY vs. Contractor

DIY sectional gutter is genuinely accessible: material runs a few dollars per linear foot, and the work is measuring, snips, and a drill. The real costs are ladder time and ladder risk — this is work performed entirely at height, often over hard surfaces, and that is the honest reason many people hire it out.

Seamless aluminum is contractor territory by definition: it is roll-formed on site from a truck-mounted machine, so there is no DIY version. Our pricing dataset carries seamless aluminum K-style at roughly $11 per linear foot installed, from 2026 contractor guides quoting a $9–13/LF installed range (sectional runs $4–8/LF), with old-gutter removal adding roughly $0.50–1.50/LF. The tradeoff is real: seamless means no joints along the run, and joints are where gutters leak. See what drives gutter costs for the full breakdown.

Related Guides

Gutter Sizing & Materials — 5-inch vs 6-inch, K-style vs half-round, and the four material choices
How Much Gutter to Order — Sections, downspouts, elbows, hangers, and end caps
What Drives Gutter Costs — Seamless vs sectional, material, height, and removal

Related Calculators

Gutter Calculator — Linear feet, downspouts, elbows, hangers, and end caps
Roofing Calculator — The roof draining into these gutters
French Drain Calculator — Where downspout discharge goes if you bury it

Written by Daniel McCarney — AceCalc