Seam tape at a glance
- Fully taped
- Every seam
- Critically taped
- Shoulders and hood only
- Fails by
- Lifting at the edges with age
Why seams need taping at all
Sewing two pieces of waterproof fabric together punches a line of holes through both. The fabric can be rated to 20,000 mm and it makes no difference at the seam. Seam tape is the strip bonded over that line on the inside to close the holes, and it's applied with heat and pressure rather than glue.
Fully taped against critically taped
Brands describe coverage two ways. Fully taped means every seam; critically taped means only the ones judged most exposed, usually shoulders and hood. Critically taped is cheaper and lighter and it's a genuine compromise, so it's worth knowing which one you're buying before it rains sideways.
Why tape is what ages first
Tape is also the part that ages worst. Look inside an old shell and you'll often find the tape lifting at the edges, curling, or peeling away in strips. Once that starts the garment leaks at the seam and the repair is fiddly. Gear repair tapes and seam sealants can buy time, but a shell with tape failing in several places has reached the end.
What this means when you're choosing
- Fully taped rather than critically taped if you hike in real weather
- Tape edges inside a used jacket, which is where failure starts
- Narrow tape on lightweight shells, which saves weight and is more delicate
The common mistake
Assuming a waterproof rating covers the seams
Every stitch is a hole. A 20,000 mm fabric with an untaped seam leaks at that seam and the rating tells you nothing about it. On silicone-coated shelters tape will not bond at all, so those ship unsealed and you do it yourself.
Common questions
What's the difference between fully taped and critically taped?
Fully taped seals every seam. Critically taped seals only the most exposed ones, leaving the rest to leak slowly in sustained rain. For a jacket you'll rely on in bad weather, fully taped is worth the extra.
Can lifting seam tape be repaired?
Sometimes. A warm iron through a cloth can re-bond tape that's just starting to lift, and a liquid seam sealant works on small sections. Widespread peeling isn't practically fixable.