Ice, and the thing gutters get wrongly blamed for

A hard continuous freeze is in some ways easier on a building than what this region actually gets. Water that freezes once and stays frozen is inert. Water that freezes overnight, thaws in the afternoon sun on a south elevation, runs, and freezes again after dark, is doing work on your house every single cycle, and it does it dozens of times a winter.

Ice in the trough

Water sitting in a gutter freezes. If the run has correct fall and drains fully, there is very little water in it to freeze and this hardly matters. If the run has a low spot holding standing water, you now have a block of ice in the exact place where the metal was already stressed and the hangers were already carrying the most load. Ice expands as it forms and it does not care what is in the way.

This is why the sag conversation and the winter conversation are the same conversation. A gutter that drains cannot ice up badly. A gutter that ponds will. Pitch and sag is the page that matters here.

Icicles are information

An impressive row of icicles along a gutter looks like winter in a photograph and is actually a diagnostic reading. It means water is running off the roof and freezing at the edge, which means something warmer than freezing is melting snow up on the roof surface while the eave is cold. That is almost always heat getting into the attic, which means the story is insulation and ventilation, not gutter.

Ice dams, and where the blame actually sits

An ice dam forms when snow on a warm upper roof melts, the meltwater runs down to the cold overhang, and refreezes there. The refrozen ridge then traps the next lot of meltwater behind it. That trapped water sits on shingles, and shingles are designed to shed running water, not to be a waterproof membrane holding a pond. Given long enough it finds a way under a course and into the house.

Now the important part, because this is where the trade routinely misleads people: the gutter does not cause the ice dam. The dam forms at the roof edge, and it would form on a house with no gutters at all. What the gutter does is give the ice somewhere to sit and grow, and then take the weight of it.

Which means two things follow. Ripping the gutters off will not stop ice dams. And blaming the gutter installer for an ice dam is usually blaming the wrong trade, because the cause is up in the attic: heat escaping into the roof space, uneven insulation, bypasses around lights and pipes, and ventilation that is not carrying that heat away.

What actually breaks in a St. Louis winter

• Hangers and spikes. A trough full of ice is far heavier than a trough full of water, and it is a rigid mass that also gets shock loaded when snow slides off a steep plane above.
• Seams on sectional gutter. Sealant is at its least forgiving when cold, and the joint is being flexed by thermal movement at the same time.
• Downspouts. Water standing in the bottom elbow freezes solid, then the column above it has nowhere to go. Buckled downspouts after a cold snap are common and are the cheapest thing on this list to replace.
• The outlet of a buried line. Shallowest point, most exposed to air, and often obscured by autumn leaves nobody cleared. Detail here.
• Walkways. Discharge onto a path in December is an ice rink in January. This is a safety issue and it is fixed by moving the discharge, not by salting the same spot all winter.

What to do before the first freeze

The single highest value job in the gutter year is clearing the runs after the leaves have finished falling and before the first hard freeze, because everything you leave in there is going to be frozen into a solid mass for the winter. Second is checking that each downspout runs clear all the way to its discharge point, which means putting a hose in the top and going to look at the bottom. Third is making sure winter discharge is not landing on anything anyone walks on.

None of that requires buying anything. The full calendar is here.