Vinyl Siding in St. Louis

Thickness, gauge and what makes a panel stiff

The code floor is 0.035 inch. That is the nominal thickness Table R703.3(1) of the residential code lists for vinyl siding, and section R703.11 requires the siding to be labeled as meeting ASTM D3679 by an approved quality control agency. Under the industry's program, that agency makes two unannounced plant inspections a year and tests panels pulled from the line.

Panels on the market run from about 0.035 to 0.055 inch. A thicker panel is less likely to droop and wave in summer heat, but the overlaps where panels meet show more, and the Journal of Light Construction's field guide notes that most installers prefer the middle of the range, around 0.042 to 0.044 inch.

Thickness is not the whole story. The same guide's point is that stiffness depends more on the shape of the panel, meaning the depth of the butt edge and the design of the lock, than on the thickness of the vinyl. The nail hem matters too: a double-thick hem is less likely to tear through in a windstorm. If someone quotes you a "gauge," ask for the thickness in thousandths of an inch on the manufacturer's spec sheet, and look at the hem.

Insulated vinyl: what the foam really adds

Insulated vinyl is a vinyl panel with rigid foam fixed to the back. The code requires it to be labeled as meeting ASTM D7793 (IRC R703.13), and that standard sets a minimum of R-2.0. The energy code wants the tested R-value printed on the package.

Put that number next to the wall itself. In this climate zone the 2015 energy code calls for R-20 in the stud cavity, or R-13 in the cavity plus R-5 of continuous insulation outside it. An R-2 foam backer is well short of that R-5 layer. Where the foam earns its keep is over the framing. The Department of Energy's Building America guide notes that studs, plates and the framing around doors and windows make up nearly a quarter of a typical wall and insulate at about R-1 per inch, and foam on the outside is the only layer of a re-side that covers them.

Two practical points. The same guide says insulated siding only counts as insulation when it is installed directly over the water-resistive barrier and sheathing, not over furring strips alone. And because the panel is thicker, trim and window and door openings may need to be built out to receive it.

How vinyl should hang on the wall

Unless the maker's instructions say otherwise, the code's default fastener is a nail with a 0.120-inch shank and a 0.313-inch head, reaching at least 1-1/4 inches into sheathing and framing combined, no more than 16 inches apart on horizontal siding and 12 inches on vertical (IRC R703.11.1). The vinyl industry's installation manual adds the details that keep a wall flat:

• Nail in the center of each slot, starting from the middle of the panel and working out to the ends.
• Leave a gap of 1/4 inch where panels run into corner posts and channels, and 3/8 inch when the work is done below 40°F.
• Lap panel ends about an inch, half the length of the factory notch, with the laps facing away from entrances and the usual line of sight.
• Lock each panel fully, but do not pull it up or push it down while nailing. It should slide side to side once fastened.
• Under windows and at the top of a wall, punch the cut edge every 6 inches so its raised lugs catch in utility trim, rather than face-nailing.

One exception from the field guide is worth knowing on two-story houses: at the band joist between floors, keep slight upward pressure on the lock, because the framing shrinks and can pull a panel down until it unlocks and flaps in the wind.

Heat: reflected sunlight and dark colors

The vinyl industry's own bulletin on concentrated sunlight explains the problem that warps siding on otherwise good jobs. Most cases trace to double-pane windows whose glass has bowed inward because the pressure between the panes differs from the air outside. The bowed glass acts like a concave mirror and focuses reflected sun onto a narrow strip of wall. Low-E glass makes it worse because it reflects more of the sun's infrared heat. The bulletin says light and dark colors can both be damaged, and that paint, other claddings and even house wrap under construction have been hurt the same way.

The fixes all block the beam: a tree or shrub in the path, an awning or sunshade over the offending window, or a screen on that window, which may cut the reflected energy enough on its own. If the window belongs to a neighbor, it is a conversation, not a repair. Read the siding warranty's exclusions before assuming the damage is covered.

Ordinary sun matters too. Vinyl has mostly been sold in lighter colors to keep surface temperatures down. Darker shades have improved, but a panel that gets hot enough can still droop.

Hail, cold snaps and wind

Hail. Vinyl cracks rather than dents, and how easily depends on the temperature when the stone hits. The only published head-to-head test, paid for by an engineered wood maker, broke vinyl with 1.25-inch hail at 57 mph. Cracked vinyl lets water at the barrier, so it is functional damage, not cosmetic. What a claim turns on here is usually matching; see hail damage to siding.

Cold. Panels shrink in winter and stiffen. That is why the manual asks for the wider 3/8-inch gap on cold installs, and why a winter job needs more care at the channels, not less.

Wind. Vinyl is hung loose on purpose, so wind performance comes down to the nail hem and the nailing. St. Louis County's code table lists a 115 mph design wind speed. At that speed the IRC's siding attachment table (R703.3.2) puts no height limit on standard fastening for a house in suburban or wooded terrain, and caps it at a 50-foot roof height in open country. The product's tested wind rating and the 16-inch nail spacing are what to check, not the brochure.

Color, fading and cleaning

Vinyl is not painted, so there is nothing to peel, but its color can fade and its surface can chalk. The industry certifies color retention separately from the panel itself: colors tested to ASTM D6864 (solid colors) or D7251 (multi-hued colors) must pass an outdoor weathering study for each color. Ask whether the color you like carries that label, especially for a darker shade.

Chalking is the white film that shows up as vinyl oxidizes. The field guide notes it is worse in humid climates and more visible on dark panels. St. Louis sits in climate zone 4A, mixed-humid, so expect it on older dark siding.

To clean it, use a long-handled brush with soft bristles and a detergent-and-water solution, working from the bottom up so the wash water does not streak. Stiff brushes and abrasive cleaners change the gloss and leave the wall blotchy.

Write down the manufacturer, product line, profile and color name when the job is done, and keep a few spare panels. Colors and profiles get discontinued, and after a hailstorm those details decide whether a repair can match.

Where vinyl is restricted around St. Louis

Vinyl is welcome in most of the metro, but not everywhere:

• Town and Country writes a flat prohibition on vinyl siding and vinyl soffits into the architectural criteria its review board applies.
• City of St. Louis historic districts set their own material standards. Shaw's do not allow siding of any kind, and Lafayette Square expects brick on structures visible from the street. See historic districts.
• Kirkwood goes the other way. Its architectural guidelines list high-quality vinyl among the preferred wall materials.

Permits vary just as much. Outside its historic districts, the City of St. Louis exempts new vinyl siding when no window or door opening changes. University City exempts vinyl or prefinished metal installed over existing walls with openings unchanged; fiber cement and wood are not on its list. The full table is on our permits page.

What vinyl siding costs here

The 2025 Cost vs. Value Report puts a vinyl siding replacement at $18,907 in the West North Central region, with a resale value of $15,365, or 81.3% recouped. The national average for the same project is $17,950, recouping 96.5%. The project is defined as 1,250 square feet of existing siding replaced with vinyl installed to the manufacturer's specifications, factory trim at all openings and corners, and a continuous water-resistive barrier underneath.

Your number moves with:

• standard or insulated panels, and the thickness and profile you choose;
• trim: most aluminum trim coil is a nominal 0.019 inch, and the heavier 0.022 to 0.024 inch coil costs roughly 20% more, according to the field guide;
• wall height, the number of openings and corners, and what has to come off first;
• rotten sheathing, priced at the square-foot rate in your written estimate;
• lead-safe work on a house built before 1978.

See siding replacement for how the whole job runs.

Common questions about vinyl siding in St. Louis

Where we work

Vinyl siding 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: