How gutters and downspouts go on

What this job puts up

One 30 ft eave gets a seamless 5 in K-style aluminum gutter that drains to a single 2×3 in downspout at the right end. Every part is below, in the order the steps use it. Screws, rivets and hanger screws are not listed.

≈4–6 hr for a small crew

This guide shows the sequence, not a design. Gutter size, the number of downspouts and where they go depend on the roof area draining to them and local rainfall. Your installer sizes them.

Check the fascia

Everything hangs from the fascia, the board along the roof edge. It has to be sound and straight before a gutter goes on it.

• Sight down the fascia for sags or waves. The gutter will follow it.
• Probe for soft wood. Replace rotted sections before anything hangs on them.

≈30 min, more if boards need replacing · 30 ft eave · 2×6 fascia

Parts: 1 × Fascia board, 2×6 × 8 ft (only where rotted)

The hanger screws need solid wood behind them. This is also when to confirm the drip edge along the roof edge is in place and sound. The gutter tucks up behind it in step 5.

Snap the slope line

Gutters aren’t hung dead level. A chalk line on the fascia sets a slight, steady fall toward the downspout end, so water keeps moving instead of sitting.

• Mark the high end just under the drip edge, at the end away from the downspout.
• Mark the low end at the outlet, then snap the line between the marks.

≈15 min · 30 ft run · ¾ in fall at ¼ in per 10 ft

Parts: 1 × Chalk line (layout tool)

The right fall comes from the gutter manufacturer. About ¼ in per 10 ft is common, and some call for more. It’s too small to see at this scale, and that’s intended: from the street, a gutter should look level.

Form the gutter and cap the ends

Seamless gutter is roll-formed on site from a coil of aluminum, in one piece the full length of the eave. On the ground, end caps go on both ends.

• Cut the run to length as it comes off the machine.
• Crimp or rivet each end cap on, then seal the seam from the inside.

≈30 min · 1 piece · 30 ft · no seams along the run

Parts: 1 × Seamless gutter, 5 in K-style aluminum, 30 ft; 2 × End cap, 5 in K-style; 1 × Gutter sealant, tube

With no seams along the run, the joints left to leak are the end caps and the outlet. Seal them with a sealant made for gutters, following the tube.

Cut in the outlet

At the low end, a hole is cut in the gutter bottom and a drop outlet is set into it from inside. The downspout will slide over the outlet’s tube.

• Mark the outlet a few inches in from the end cap and cut the hole.
• Set the outlet, fasten its flange and seal it.

≈15 min · 1 outlet · 2×3 in · at the low end

Parts: 1 × Drop outlet, 2×3 in

One downspout is typical for a short run like this. Longer runs (often past about 35–40 ft) or larger roof areas get a downspout at each end, with the gutter pitched from the middle toward both. Your installer works it out from the roof area and local rainfall.

Hang it on hidden hangers

The gutter goes up in one piece. Its back slides up behind the drip edge, so water coming off the roof lands inside the gutter, and its top follows the chalk line.

• Tuck the gutter back up behind the drip edge along the whole run.
• Clip a hanger under the front lip every 24 in and drive its screw through the gutter back into the fascia.

≈45 min · 15 hangers · 24 in on center · first and last 12 in from the ends

Parts: 1 × Seamless gutter, 5 in K-style aluminum, 30 ft; 15 × Hidden hanger with screw

A 24 in spacing is common. Follow the gutter and hanger manufacturer, and space them closer where they call for it. Screws go into solid fascia, and into the rafter tails behind it where they line up.

Run the downspout

Two elbows carry the water from the outlet back under the eave to the wall. From there the downspout runs straight down, strapped to the wall.

• Slide the first elbow over the outlet, then join it to a second elbow at the wall with a short cut piece.
• Strap the downspout to the wall near the top, middle and bottom.

≈45 min · 2 elbows · ≈6 ft drop · 3 straps

Parts: 2 × Elbow, 2×3 in; 1 × Downspout, 2×3 in aluminum, 10 ft length; 3 × Downspout strap

Each upper piece fits inside the one below it, so water can’t run out at a joint. Fasten every joint with short screws or rivets. Strap spacing varies by product; follow the downspout maker.

Send the water away

At the bottom, an elbow turns the water away from the house, and an extension carries it out onto a splash block.

• Turn the bottom elbow away from the wall.
• Run the extension out and set a splash block where it lets go.

≈20 min · Discharge ≈5 ft from the wall, measured from the wall face

Parts: 1 × Elbow, 2×3 in; 1 × Extension, cut from downspout stock; 1 × Splash block

Many guides call for about 5 ft, and code requires at least that where soils are expansive, unless the water goes into an approved drain. Check your local code, and make sure the ground slopes away from the house.

Done

That’s one eave, start to finish. Run a hose into the high end: water should reach the outlet with no drips at the caps, outlet or joints.