Storm Flap
A storm flap is a strip of fabric covering a zip, stopping water from tracking through the teeth and into the garment.
Standard zips are not waterproof. A storm flap is the cheapest and most common way to fix that, and its absence on an exposed external zip is a direct route for water regardless of the fabric rating.
The three approaches
- Storm flap: a fabric cover, sometimes secured with velcro or press studs. Cheap, effective, adds a little bulk.
- Water resistant zip: a coated or laminated zip that resists water without a flap. Cleaner, stiffer, more expensive, and not fully waterproof despite the name.
- Internal baffle: a fabric wall behind the zip that catches anything getting through. Common on higher-end shells.
Many good jackets use two of these together on the main front zip, and one on the pockets.
What to check
Look at every external zip, not just the front one. Chest and hand pockets are frequently left unprotected on otherwise well-made jackets, and a pocket is exactly where you put a phone. A flap that only covers the top half of the zip is a design compromise worth noticing.
Related terms
- Travel jackets with hidden pockets: where unprotected zips cause problems
- Taped seams: the other place water gets in
- Waterproof vs water resistant: what a fabric rating does not cover
- Glossary: all terms