Install proper flashing, use a drainage plane (house wrap), and leave a 1/4-inch gap between siding and trim for airflow.

Use cement backer board (not drywall), apply waterproof membrane (like RedGard or Kerdi), install proper shower pan lining, and seal all joints/corners with waterproof silicone caulk.

Clean annually with mild soap and water, inspect for cracks/pests, and repaint every 5–10 years (if painted).