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Gutter Talk: Seamless Vs. Sectional

Updated: Sep 20, 2023

What do professional gutter installers have that the average homeowner doesn’t?

Expensive gutter extruding machines, for starters.

All gutters can be categorized as seamless or sectional. Seamless gutters are installed by professionals using specialized machinery that shapes a roll of sheet metal into a continuous, straight length of gutter to fit the house. The only seams are found at corner miters and downspouts. Seamless gutters are considered more durable because the seams of sectional gutters can weaken years down the road. As outdoor temperatures fluctuate, the constant expansion and contraction of the gutters tends to crack the sealant at the sectional joints. If this happens, the seams have to be re-caulked from the inside with a special gutter sealant.

Seamless Gutters

A seamless gutter won’t have the same maintenance issues as one with seams. Furthermore, the seams of sectional gutters are visible, which some homeowners don’t like for aesthetic reasons.

For homes in areas prone to leaf accumulation, professional gutter installers offer another advantage: seamless covers to match your seamless gutters. While the gutters protect your home by handling the rain, the covers protect the gutters by guarding them from leaves, pine straw, twigs, and other such organic matter than can clog them and prevent proper drainage.

The professional installation method is to measure the roof-line, then feed sheet-metal into the shaping machines to form a rigid K-profile gutter, which is cut to the exact length needed. Next, the installers pre-attach the gutter hangers and end caps, and cut out any downspout openings as needed. The gutter cap is machine-formed in the same manner to the length needed.

I paid a visit to Tommy Mooney and Andrew Pardo of The Ultimate Gutter Guard Company in Birmingham, Alabama, as they installed a new gutter-and-cover system in my neighborhood. Professional installer Tommy Mooney uses a gutter machine to form a continuous straight run with no seams.

The gutter hangers are pre-attached at ground level.

For any gutter installation job, it helps to assemble the components on the ground and make as many modifications as possible before carrying it to roof level.

Tommy installs a rain screen that will be located below a roof valley.

The screen gets painted to match the gutter and cover.

Once assembled, the large gutter sections can be installed at one time.

The gutter cover is formed and extruded the same way.

The cover is cut to match and installed right on top of the gutter.

It was nice to see the professional attention to detail. For example, after the installers cut a valley opening in the gutter cover, they fit it with a rain screen spray-painted to match the gutter. By the way, that’s another advantage of professional gutter installation — more available color options than the typical white-painted sectional systems available from most “big box” stores.

In the end, the home gets a slick-looking, seamless, covered system that blends well into the roof line. The Gutter Guard allows the gutters to collect roof runoff while preventing leaf buildup. And believe me — for anyone living in a tree-towered neighborhood, gutter covers are a MUST to reduce maintenance.

Sectional Gutters

Seamless gutters are very nice, but you’ll also have to pay for professional installation, which is considerably more expensive than the DIY approach. For homeowners on a budget (or contractors without an extruding machine), you can pick up lengths of sectional gutter and downspouts at most “big box” stores and assemble them using folding aluminum “seamer”” pieces and gutter sealant to glue the sections.

Sectional covers for DIY’ers assemble with gutter sealant and “seamer” pieces that fold over the joints. This diagram appears courtesy of Amerimax, which has products available at Home Depot.

DIY Tips for Sectional Gutters

First step is to sketch out your gutter system on paper so you can quantify the various components required. Measure your roof line to determine the number of 10-ft. sections of gutter. Measure your wall height to calculate the number and length of downspouts you’ll need.

Next, account for the number of seamers (which are placed at joints between gutter sections), end caps, inside or outside corner miters, downspout elbows, and end drops which direct water from the gutter to the downspouts (plus flanges for the end drops). All these components will be sold at your gutter-supply store. Gutter sealant is required to seal all the joints. You’ll also need sheet-metal screws to connect the downspout sections, and downspout bands to fasten against the house.


It’s a good idea to attach a ladder stabilizer to the top of your ladder. It prevents the ladder from swaying while you stand on it. The stabilizer also provides a 10-in. standoff from the roof line, which makes it easy to work on the fascia and gutter without obstruction. The stabilizer rests on the roof, rather than on the shingles, gutter, or fascia to avoid any accidental damage from that ladder contact.


To limit your time working atop the ladder, the safest approach is to assemble as much of the gutter system on the ground as possible. But keep the sections small enough to carry up the ladder safely.

A sectional gutter requires an “end-drop” at each downspout location. You can carefully cut an end-drop in the bottom of the gutter or attach a sectional end-drop.

To join the end-drop to the gutter—or to join any gutter section to another—requires a “seamer.” The seamer is a piece of aluminum that matches the gutter in size and shape. First thoroughly apply gutter sealant to the side of the seamer piece that will contact the gutter from below. Butt the gutter sections together, then wrap the seamer around the joint from below. Bend the front of the seamer so it hooks over the front edges of the butted gutters. The back edge of the seamer extends above the rear of the seam, and you fold this metal flap over the edge of the gutter sections. Use pliers to crimp the front and rear lip of the seamer tightly onto the gutter. Cover the seam inside the gutter with a generous bead of sealant.

A gutter’s end cap will be shaped and sized to match the gutter. Install it by caulking the edges with gutter sealant and pushing the end of the gutter into the seams of the end cap.

It’s also a good idea to install the end-drop flanges into the gutter section while it’s still on the ground. The flanges provide a mounting place for the downspouts, which will be installed after the gutter is in place.

These days, gutters are fastened to the house using the hidden hangers with integrated screws. Clip the hangers in place every couple of feet along the length of the section. Make sure to locate a fastener near the end of each section to minimize stress at the joint locations.

Before installing a gutter section, give the sealant a few hours to dry and gain some rigidity at the joints.

Assemble as much gutter on the ground as possible. Paint the gutter prior to hanging it.

All joints must be sealed with a quality gutter sealant like the WeatherMaster brand from Titebond.

Crimp the connections together with pliers.

A buzz-cutter (AKA oscillating multi-tool) with a metal-cutting blade is handy device for cutting end-drops into a gutter when necessary.

Cut away the flaps from the end-drop hole, apply sealant to the rim of the flange outlet, and insert it into the hole flush with the bottom of the gutter. The downspout connects to the flange outlet.

Attach “hidden” gutter hangers every couple of feet.


Mark gutter layout on the house fascia with a chalk line. At one corner, mark the highest point of the gutter run 1-1/4 in. below the roof line (or drip edge flashing if installed). Unreel the chalk line and move the gutter to the opposite end of the fascia. At that corner, first level the string, and then drop the downspout end of the gutter about 1 inch per 20 feet and snap the chalk line. This achieves a slope that helps gravity pull water to the downspout locations.

Note that gutter sections longer than 35 feet should have a downspout at each end. In this case, make two separate chalk lines, pitching the gutter from the center to each downspout.

Drive the screws of the hidden hangers into the fascia, being careful not to drive them too tight, which can bend the hangers and distort the gutter’s shape. If you don’t have a solid wood fascia to hold the fasteners, you will need to locate the rafter tails. These 2x framing members should be located every 16 inches behind the fascia. Mark the tails along the chalk line and pre-drill the fastener holes to prevent splitting the wood with the gutter screws.

Avoid over-tightening the gutter hangers, which will crush the gutter.

The drip edge flashing at the roof line should overlap the edge of the gutter to direct water into the trough.


Once your gutters are installed, the downspouts are your final piece of the puzzle.

Use screws and sealant to fasten a flange outlet inside the hole of each end drop.

Duct-tape an elbow section onto each flange outlet. Use a straight edge to follow the path of the elbow to the wall where the second elbow will be located. Tape the second elbow in place on the wall. Measure the downspout section needed to install between the two elbows. Each downspout and elbow has one end crimped; the larger end

fits over the smaller end to form a slip joint. Account for the overlapping slip joint when measuring—usually about 1 inch of downspout overlapping the elbow at each end.

Assemble your downspout at ground level, driving two primed aluminum screws into pre-drilled holes at each joint. Avoid leaks by making sure the upper downspout sections tuck into the lower sections.

Nail or screw the downspouts snugly against the wall using two flexible downspout bands per each 10-foot section. Duct tape will hold the downspout stationary while fastening.

Attach a front or side elbow at the bottom of the downspout. Finally, use drain extensions or splash blocks to direct water away from the building foundation.

We recommend DIY’ers limit their gutter installation adventures to first-level roof lines. For multi-level homes, your safest move is to call a pro.

You can also retrofit your gutters (seamless or sectional) with a variety of different gutter-cover products to prevent leaves and debris from building up and causing clogs.

However, if you’re not comfortable working at heights and you have a multi-level house, then professional installation is probably the smart way to go.

When it comes to leaf and debris accumulation, this is the kind of crap we have to deal with on a regular basis in our neighborhood.

Clogged gutters aren’t much fun to clean.

To end the clogged-gutter madness, I installed retro-fit gutter covers at my home. These can be applied to sectional or seamless gutters.

The product shown here simply snaps onto a K-profile gutter with no need for tools.


Cutting Gutters to Size

When assembling the gutter and downspouts, you will likely have to cut some of the materials to length. One method is to clamp the gutter sections to a couple of saw horses and cut using a hacksaw. A pair of metal snips can also do the job, but it can be tough to keep the cuts clean and straight.

Another option is to use a 12-in. miter saw with a fine-toothed blade turned backwards. The speed of the blade combined with the backwards teeth make a straight, clean cut with very little effort. When cutting gutter material on the miter saw, turn the section upside down so the blade enters the underside of the gutter rather than the top edges. After cutting, be sure to return the blade to its original cutting direction so nobody uses the backward blade when not intended.

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1 Comment

May 20

Great read on the differences between seamless and sectional gutters! It’s super helpful to understand both the low-maintenance appeal of seamless options and the budget-friendly advantages of sectional gutters. Your practical tips for installation are invaluable, making this a perfect guide for homeowners deciding on the best gutter solution for their needs. Thanks for the thorough breakdown—very enlightening! For those looking for professional assistance, consider Roof Repairing in Sterling VA.

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