Rain here tends to arrive in short, heavy bursts, and a gutter either keeps up or spills over the front edge. This page covers sizing, metals near salt water, guards, downspouts and the wood the gutter hangs on.
Many gutter problems are not about the gutter at all. They are about where the water ends up: against a crawl space wall, in a flower bed that never dries, behind a fascia board that has been soft for two summers, or over the top of a trough that was sized for a drizzle. A gutter system is a drainage system that happens to be hung on the roof edge, and it should be judged by where it puts the water.
Below: how much water a roof here actually sheds, why the short downpour matters more than the yearly total, what the code requires, which metals to think about near salt water, what guards can and cannot do, where downspouts should end, the wood behind the gutter, and what hurricane season asks of the hangers.
NOAA's 1991–2020 climate normals for Charleston International Airport put the average year at 52.51 inches of rain, with 19.78 inches of it falling in June, July and August alone. The same normals count, on average, about 15.7 days a year with an inch of rain or more and about 4 days with two inches or more.
The arithmetic is simple. An inch of rain on 1,000 square feet of roof is about 83 cubic feet of water, or roughly 620 gallons. A 2,000-square-foot roof in a two-inch afternoon storm sends close to 2,500 gallons to its gutters, and every one of those gallons has to come down a downspout somewhere. On a house with a hip roof, that load is spread around the whole perimeter. On a gable roof it lands on two long eaves. Where two slopes meet in a valley, a large share of both pours into one short stretch of gutter, which is where overflow starts.
A gutter does not care how much rain falls in a year. It cares how much falls in the worst few minutes. NOAA's Atlas 14 precipitation-frequency estimates for downtown Charleston put a one-hour rain that comes about once in ten years at 3.02 inches, and the most intense five minutes of such a storm at a rate of 9.50 inches an hour. Even the one-hour rain expected every two years is 2.11 inches.
That is why we size from the roof, not from habit:
We hang both 5-inch and 6-inch gutters, formed on site from aluminum coil to the length of each run, so there is no splice for a leak to start at.
Less than most people expect. The residential code South Carolina enforces requires a controlled way of carrying roof water away only where expansive or collapsible soils are known to exist; there, roof drainage has to discharge at least 5 feet from the foundation walls or into an approved drainage system (Section R801.3). Everywhere else, gutters are a choice the code leaves to you.
That does not make them optional in practice. Water that falls off an eave splashes back onto siding, wets the bottom of the wall and soaks the ground right where the foundation sits. On a raised house it runs under the floor. The code's 5-foot figure is a sensible target for where any downspout ends, soil or not.
Two local things can affect a gutter job. In a historic district, exterior changes visible from the street can need review; the City of Charleston's Board of Architectural Review covers street-visible exterior work in the Old and Historic District, so a change of gutter style there is worth a call to the preservation staff first. And many towns require the company doing the work to hold a local business license; each town page says who issues permits there.
Three metals cover nearly every house here:
Near the water, the details matter more than the trough. The residential code's default rule for metal roofs is a useful habit for gutters too: it pairs galvanized fasteners with steel, and copper, brass, bronze or 300-series stainless with copper, and accepts stainless with any metal (Section R905.10.4). Apply the same habit to a gutter: hangers, screws and straps chosen to suit the gutter metal, written down on the quote.
Guards come in a few families. Screens and perforated covers stop leaves but let small debris through. Fine micro-mesh stops more, including pine needles and roof grit, but its surface can film over with pollen and dirt and needs brushing. Solid covers that curve water around a nose rely on the water clinging to the edge, which works in a steady rain and less well in the hard bursts described above. Foam and brush inserts sit inside the trough and catch debris in place.
What none of them does is end maintenance. Every guard still needs a look after leaf drop and after a storm, and some need lifting to clear what slipped underneath. A guard also changes how a roof edge is serviced: some clip under the first row of shingles, so a roof replacement means taking them off and putting them back.
Our advice is to match the guard to what is overhead. Under pines, a fine mesh. Under broad leaves, a sturdy screen or cover. On a house with no trees nearby, maybe nothing but a twice-a-year cleaning. We offer leaf protection as an option on every gutter quote, priced as its own line, so you can see what it adds.
A downspout that ends at the corner of the house has moved the problem about two feet. Water dumped there soaks the soil next to the foundation, splashes the bottom of the siding and, on a raised house, runs under the floor where it keeps a crawl space damp in a climate that is already humid.
What a good layout does:
Re-routing downspouts is often the cheapest fix on a house with a wet crawl space or a stained wall, and we quote it on its own when that is all a house needs.
A gutter is only as solid as the fascia board it is screwed to. Termites are part of the climate here: the code design table the City of Charleston publishes puts the local risk of termite damage in its very heavy class, with weathering listed as moderate. Fascia that stays wet behind an overflowing gutter softens, and soft wood draws insects.
Before new gutters go up, the fascia should be checked by hand along its whole length, and soft sections cut out and replaced before any hanger goes in, because a hanger screwed into rot will pull out the first time the gutter fills with water or a storm pushes on it. The roof edge matters too. Metal edge flashing at the eave should lap into the gutter so water that runs under the shingle edge ends up in the trough and not on the wood. South Carolina's code requires drip edge on a shingle roof only where the shingle maker calls for it, but on the roofs we replace it goes on anyway.
The National Weather Service warns that signs, roofing material and other items left outside can become flying missiles in a hurricane. A long run of gutter pried loose by wind is one of those items, and it can take fascia and roof edge with it.
Before the season starts in June, it is worth checking that the hangers are tight, that the downspouts are strapped to the wall and that nothing is already pulling away. A gutter packed with leaves also weighs far more than an empty one, and in a tropical downpour it fills in minutes. After a storm, look for sagging runs, a gap between the gutter's back and the fascia, and downspouts knocked off their outlets. If you want a second pair of eyes, our free inspection covers every slope and the gutters, with photos you keep. The hurricane roof protection page has the rest of the pre-season list.
It depends on how much roof drains into each run, how steep it is and where the valleys empty. Downtown, NOAA puts a once-in-ten-years one-hour rain at about 3 inches, with the worst five minutes falling at a rate of 9.5 inches an hour. Big roofs, steep pitches and valley-heavy runs often justify 6-inch.
Only in one case. The residential code requires controlled roof drainage where expansive or collapsible soils are known, discharging at least 5 feet from the foundation. Elsewhere it is your choice, though water dropped at the foundation causes its own problems.
No. Guards cut down how often you clean and how bad it gets, but every type still needs checking after leaf drop and after storms. Fine mesh can film over with pollen and grit, and solid covers can be overshot in a hard downpour.
Aluminum is what we hang, and the details around it matter as much as the trough. The code's default rule for metal roofs matches the fasteners to the metal, and the same habit suits gutters: ask what the hangers, screws and straps are made of, and have it written on the quote.
Not always, but the roof edge has to be reachable. Guards clipped under the first course of shingles come off and go back. If the gutters are old or the fascia behind them is soft, the replacement is the cheapest time to redo them.
Usually because water has been getting behind the gutter: overflow from a clogged or undersized trough, or a roof edge without flashing that laps into it. The city's code design table puts termite risk in its very heavy class, and wet wood draws them.
Gutters across greater Charleston, from the sea islands and beach towns to Summerville, Goose Creek and Moncks Corner. Each city has its own page with the permit rule and code edition that apply there:
Sources: NOAA NCEI, 1991-2020 annual and seasonal climate normals, Charleston International Airport (USW00013880) · NOAA Atlas 14 precipitation-frequency estimates (intensity), downtown Charleston, 32.7765 N 79.9311 W · 2021 International Residential Code as adopted in South Carolina, Chapter 8: R801.3 roof drainage (UpCodes) · 2021 International Residential Code as adopted in South Carolina, Chapter 9: R905.2.8.5 drip edge, R905.10.4 fasteners (UpCodes) · City of Charleston design criteria table (termite damage, weathering) · City of Charleston, Board of Architectural Review · National Weather Service, Hurricane Safety. Codes, programs and prices change; confirm the current rule with your city before you rely on it.
Free inspection, a written scope, and photos you keep either way.
Book my free inspection →
