Gutters fail here in a few predictable ways: too small, pitched wrong, packed with leaves in fall, iced in winter. This page covers materials, sizing, the roof edge, every common guard, and where the water should end up.
A gutter has one job: catch what the roof sheds and put it somewhere other than beside your foundation. That is a lot of water here. NOAA's 1991 to 2020 normal at Lambert is 41.70 inches of precipitation a year, and by our arithmetic every 1,000 square feet of roof sheds about 26,000 gallons of it (3.475 feet of water over 1,000 square feet is 3,475 cubic feet, at 7.48 gallons each). Funnel that through four downspouts and one soggy corner becomes a wet basement wall.
We form aluminum gutters on site in 5- and 6-inch sizes, hang them on hidden hangers and re-route downspouts. The rest of this page is how to judge that work, whoever does it.
Gutters come two ways. Sectional gutters arrive in stock lengths and get joined on the house. One-piece gutters are rolled from a coil of aluminum by a forming machine at the house and cut to the length of each run, so the only joints left are at corners, end caps and outlets.
The joints are what matter. InterNACHI's roof-inspection manual, written for home inspectors, says steel gutters come in short lengths and so carry joints all along the run, and that rust and leaking joints are their two main problems. It credits aluminum formed on site with fewer joints, then warns that the aluminum pop rivets used at corners and outlets very often fail from impact or from the house moving. A one-piece run still needs its corners sealed and checked.
Vinyl, sold off the shelf at home centers, is what the same manual calls the do-it-yourself material of choice.
| Material | What to know | InterNACHI life estimate |
|---|---|---|
| Aluminum | Light, does not rust, can be formed on site; dents from ladders and limbs | 20 to 40+ years |
| Copper | Soldered joints, including downspouts; the long-life choice | 50+ years (downspouts 100) |
| Galvanized steel | Stands up to knocks; rusts without upkeep | 20 years |
| Vinyl | Sold in kits for do-it-yourself installs; can crack | 25+ years |
DOE's builder guide adds that copper and galvanized steel shrug off ladders and falling branches better than vinyl and aluminum, which crack or dent. On shape, it treats K-style against half-round as a question of looks, with no real gap in performance.
Looks can be regulated, though. In a St. Louis City historic district, the city's permit rules require approval for gutters and downspouts even though the building code does not, and the Cultural Resources Office wants a permit for every exterior change there short of repainting wood trim. District standards differ. Fox Park's, for one, treat ordinary gutter replacement as maintenance but require a gutter built into a cornice to be rebuilt within the original cornice profile, and recommend copper, painted galvanized steel or non-reflective aluminum over plastic on the street side.
Gutters are sized for the worst few minutes of a storm, not the annual total. NOAA's Atlas 14 puts the 5-minute downpour downtown St. Louis should expect about once a decade at 7.46 inches an hour, and the once-a-century burst at 10.9. SMACNA's sizing calculator, built on its sheet metal manual, starts from local rainfall data too.
The Department of Energy's rules of thumb for a house:
SMACNA treats 50 feet as the practical limit for gutter served by one downspout, because of thermal expansion. InterNACHI warns that too much pitch causes its own trouble, with water fast enough to spill over corners and end caps. A 6-inch gutter with 3-by-4 downspouts earns its place where a big roof plane or a valley empties into one run, or where the wall has no spot for another downspout; for mixed-humid climates like ours, DOE advises extra capacity.
Water reaches the gutter by way of the drip edge. The 2018 IRC puts drip edge on every eave and rake of a shingle roof, hanging at least a quarter inch below the sheathing, with the underlayment lapped over it at the eaves so anything running down the underlayment lands on metal and drops into the gutter (R905.2.8.5). Missouri has no statewide code, so each city adopts its own edition; Pacific reprints this section of the 2018 IRC word for word in its roof-code handout.
Hang the gutter too low, or let the shingles stick out too far past it, and hard rain jumps the gutter entirely, InterNACHI notes. Its manual also prefers brackets fastened through the fascia into the rafter tails over brackets held only by a thin fascia board. Where a roof edge runs into a wall, the code wants flashing that turns the water away from the wall (R903.2.1), the piece usually called a kick-out.
No guard ends maintenance; This Old House's review of the types says they all need occasional upkeep. What they change is how often you climb the ladder.
| Type | How it works | The catch |
|---|---|---|
| Screen or perforated cover | A grid over the gutter stops leaves | Bigger openings let pine needles and shingle grit through (This Old House) |
| Micro-mesh | Very fine mesh on a frame filters grit and needles | Needs precise fitting to the gutter and roof edge (This Old House) |
| Reverse-curve hood | Water follows a curved lip into a slot; leaves slide off | Struggles with heavy volume, shows from the street, and holds snow and ice on the curve (This Old House) |
| Foam insert | Porous foam fills the trough | Breaks down after a few seasons and holds debris and moisture on top (This Old House) |
| Brush insert | Bristles fill the trough and catch leaves | Needs regular cleaning; wet leaves mat into it (This Old House) |
In 16 months of outdoor tests published in 2010, Consumer Reports found very fine mesh did better than coarser screens, none of the foam or brush inserts kept debris out well, and even the top screen was only middling in a severe downpour. DOE adds that debris left in a gutter invites nesting animals. Before any guard goes on, ask how it attaches; the roof-edge section explains why.
A gutter that empties beside the foundation has only moved the problem. The 2018 IRC wants the ground to fall at least 6 inches within the first 10 feet from the house (R401.3), and where expansive or collapsible soils are known, roof water must be released 5 feet or more out, or into an approved system (R801.3). DOE's guide puts it in practice: run downspout water out five feet or more through solid, not perforated, pipe falling 5/8 inch or more per foot, or ten feet to an underground catchment, and never into the perforated foundation drain, which only soaks the wall it protects.
In the city and most of St. Louis County there is one more rule. The Metropolitan St. Louis Sewer District tells owners never to pipe a downspout, sump pump or driveway drain into the sanitary sewer line, and to let downspouts drain onto the ground. The city is served mostly by combined sewers that carry storm water and sewage together, and in heavy storms they can overfill and back up into basements. In the neighborhoods its Project Clear work covers, MSD says it pays the full cost of removing storm water connections from private sewer lines. On the Illinois side and outside MSD's area, ask the city where storm water may go before burying a downspout.
Most gutter trouble is repairable: re-hanging a sagging run to the right pitch, resealing a leaking corner, replacing missing hangers, reattaching a downspout. InterNACHI's checklist makes a good homeowner walk-around: enough downspouts, a fall toward each one, solid fastening, no loose spikes, no dripping joints and nothing growing in the trough.
Replacement makes sense when steel has rusted through, joints leak along the whole run, or the gutters are near the ages in the table above. If a new roof is coming, time them together: FORTIFIED notes that gutters left in place during a re-roof keep the underlayment from going under new drip edge unless the drip edge is laid over them and notched around the brackets. A roof replacement is the natural moment. In St. Louis City, gutter and downspout replacement on a house of up to four units usually needs no building permit, historic districts aside. Our free inspection photographs the gutters along with every slope.
They cut cleaning; they do not end it. In Consumer Reports' outdoor tests the finest mesh did best, foam and brush inserts did poorly, and even the top screen was only middling in a severe downpour. Choose a guard that fixes to the gutter and drip edge rather than one slid under your shingles.
That turns on how much roof drains to each run, how hard the rain falls, and how many downspouts the walls allow. Each square inch of downspout serves about 100 square feet of roof, so a 3-by-4 downspout handles about 1,200. Big roof planes, valleys and long runs push toward 6-inch.
Five feet or more from the foundation through solid pipe sloped away from the house, or ten feet to an underground catchment, by the Department of Energy's guidance. The ground should also fall 6 inches in the first 10 feet. Never tie a downspout into the perforated foundation drain.
Not into the sanitary sewer. The Metropolitan St. Louis Sewer District says downspouts, sump pumps and driveway drains must never be piped into it, because storm water in those lines helps cause overflows and basement backups. Let downspouts drain onto the ground, well away from the house.
Usually not in St. Louis City, which lists gutter and downspout replacement on houses of up to four units among jobs that normally need no building permit. Inside a city historic district, approval is required for gutters and downspouts anyway. Other cities set their own rules, so we check yours.
No. Ice dams start with attic heat melting snow that refreezes at the cold eave. The Department of Energy notes that a gutter full of snow can freeze into a dam that is already forming, which is one more reason to clear or screen gutters before winter.
Gutters across greater St. Louis, from the city and St. Louis County out to St. Charles, Jefferson and Franklin Counties and across the river into the Metro East. Each city has its own page with the permit rule and code edition that apply there:
Sources: U.S. DOE Building America Solution Center, Gutters and Downspouts · U.S. DOE Building America Solution Center, Construct Roofs and Attics for Ice Dam Prevention · InterNACHI, How to Perform Roof Inspections (gutter and downspout chapter) · InterNACHI, Standard Estimated Life Expectancy Chart for Homes · 2018 International Residential Code, Chapter 9 (R903.2.1, R905.2.8.3, R905.2.8.5) · 2018 International Residential Code, Chapter 4 (R401.3 drainage) · 2018 International Residential Code, Chapter 8 (R801.3 roof drainage) · NOAA Atlas 14 precipitation frequency, downtown St. Louis (rainfall intensity) · NOAA NCEI 1991-2020 normals, St. Louis Lambert (precipitation, freezing days) · SMACNA, Downspout and Gutter Sizing Calculator notes (Architectural Sheet Metal Manual) · IBHS FORTIFIED, Technical Bulletin FH 2023-09: Leaf Guards and Gutters · This Old House, types of gutter guards (updated July 2026) · Consumer Reports, gutter guard test results (Aug 2010) · Metropolitan St. Louis Sewer District, preventing building backups · Metropolitan St. Louis Sewer District, stormwater and wastewater (combined and separate sewers) · Metropolitan St. Louis Sewer District, stormwater disconnection · City of St. Louis, residential permit criteria (gutters, historic district exceptions) · City of St. Louis Cultural Resources Office, review FAQs · Fox Park Historic District Standards (City of St. Louis ordinance) · City of Pacific, Roof Code handout (2018 IRC R905.2.8.5). 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 →
