Do I need taped seams for a rain jacket to be waterproof?

Yes — stitching alone cannot be waterproof. Every needle hole pierces the membrane and creates a leak path, which is why professional rain shells are built with seam tape heat-bonded over every stitched seam, or use sew-free welding/bonding technology instead.

Three practical checks when specifying or inspecting a rain jacket: (1) confirm full seam taping, not only shoulder panels; (2) request a seam-slippage and peel-strength spec for the tape; (3) run a shower-test on the sealed sample before bulk production. Coating-only jackets with untaped seams may pass drizzle but will leak under sustained rain or pack pressure.