When you make the decision that the smoother flow and stronger design of seamless gutters makes them right for you, you might be surprised to find that the vast majority of products are made from metal. While vinyl seamless gutters do exist, they're far rarer than their counterparts made from copper, aluminum, or steel. Find out why vinyl is often eschewed for this particular type of gutter so you can decide if it's worth the extra effort to track down seamless gutters made from it instead of metal.
First, all seamless gutters are formed from rolls of fresh material and carefully bent with a tool known as an extruder, usually on site so each section is a custom fit to your home's dimensions. For metal, the extruder only has to make simple bends to create a gutter of the exact size you want. Vinyl is much trickier to bend and requires just the right amount of heat so the material doesn't crack or snap back to its former shape. This means that vinyl seamless gutter machinery is much more expensive than the equipment for seamless metal gutters. Even when you're ordering seamless lengths from a manufacturer rather than having them made on site, you're paying extra to cover the overhead costs of the special extruders.
Vinyl is a relatively strong material for being a form of plastic, but it still has its limits when it comes to holding up its own weight. Even the thickest vinyl material tends to sag and bend in the middle, resulting in the need for more supports than you would use with any type of metal seamless gutter. Sectional vinyl gutters are reinforced by their seams because the connection of two ends with a thicker piece of vinyl adds a lot of stiffness and support for the weight of the product. Seamless vinyl gutters tend to take more work to install due to this problem as well, since extra fasteners must be used to prevent sagging.
Seamless gutters are usually designed with a folded lip so that the fastener attaching the gutter to your home's fascia boards does not penetrate through the gutter opening where water is flowing. This is known as a hidden fastener. Keeping at least one layer of material between where the water flows and where the fasteners puncture the gutter prevents rot from setting into the fascia boards thanks to the opening around each fastener. Vinyl gutters aren't necessarily made this way, even when they're seamless, because this kind of design often puts too much pressure on the vinyl and leads to cracking. Seamless vinyl gutters tend to rely on the traditional fastening method that runs the nail or screw from the inside of the gutter to the fascia board, and even self-sealing fasteners will eventually cause damaging leaks this way.
Seamless gutters are best handled by the professionals because it's tricky enough for them to get the extra-long lengths of material in place without bending or damaging them. However, if you're set on the idea of doing your own gutter installation, you definitely want metal gutters. Vinyl absolutely requires support across the entire length of the gutter during installation. Even a little bending leads to permanent sagging or tiny cracks in the plastic that become leaks after just a few years. The stiffer profile of metal gutters makes it at least a little easier to handle DIY installation.
Finally, most seamless gutter installers prefer to only offer metal gutters because they want to stand behind their product. All of the metals commonly used for these gutters are more durable than vinyl, so you're going to get better warranty offers on both material and labor by sticking with them.