Sheet E-501 · Almanac

Heat, humidity, mildew & termites: Atlanta's four examiners

Atlanta is IECC climate zone 3A, hot-humid: long cooling seasons, roughly 50 inches of rain a year, shade that never fully dries, and termite pressure among the heaviest in the country. Siding here is graded by four examiners, all year.

Examiner 1 — Heat and sun

South and west walls bake. Vinyl distorts when restrained or overheated, paint chalks and fades fastest on these faces, and dark colours raise surface temperatures sharply on any material. Detailing allowances for movement, and honest colour expectations, belong in the contract conversation before work starts.

Examiner 2 — Humidity and mildew

North walls and tree-shaded elevations grow mildew and algae on every material — it feeds on surface grime more than on the siding itself. Annual gentle washing is maintenance, not cosmetics. Behind the wall, humidity demands a correctly lapped water-resistive barrier and flashed openings; Georgia's IRC-based code (the Georgia State Minimum Standard Codes adopt the IRC with state amendments) treats the WRB and flashing as the drainage system, because the cladding alone is never waterproof.

Examiner 3 — Termites, subterranean and Formosan

Georgia hosts both native subterranean termites and Formosan termites, an introduced species whose colonies are larger and more destructive. Termites do not eat fiber cement or vinyl — they travel through and behind them to reach framing. The defences are boring and effective: clearance between siding/soil/mulch, no wood-to-ground contact, intact termite shields and inspection gaps where detailed, and a maintained treatment/bait programme with annual inspection. Engineered wood's borate treatment resists termites in the board itself; the house around it still needs the system.

Examiner 4 — Wind-driven rain and storms

Atlanta's design wind speeds are moderate by coastal standards — on the order of 115 mph ultimate under current ASCE 7-based maps for typical risk categories; confirm the figure for your address and code edition — but its storms deliver rain sideways for hours. Nailing schedules, corner and top-course detailing, and kick-out flashing decide whether that rain stays out. See also storm & hail.