Why seams leak
A waterproof membrane is a continuous sheet, but a jacket is sewn from many pieces. Every stitch is a needle hole, and thousands of holes along the seams let water in even when the fabric itself is waterproof. Seam tape covers those holes.
How tape is applied
- The tape is a narrow strip with an adhesive layer on one side, matched to the inner surface of the laminate (membrane side for 2L and 2.5L, backer side for 3L)
- A hot-air seam sealing machine heats the adhesive and a pressure roller bonds the tape onto the stitched seam
- Temperature, speed and pressure are set for the specific fabric and tape; the operator guides the garment so the tape stays centred over the stitch line
- The tape cools and sets, forming a continuous waterproof barrier
Fully taped vs critically taped
| Fully taped | Critically taped | |
|---|---|---|
| Coverage | All seams on the shell | Only the most exposed seams (shoulders, yoke, hood and top of pockets) |
| Protection | Highest | Moderate; water can enter through untaped seams |
| Cost | Higher: more tape and machine time | Lower |
| Used for | Technical and premium shells | Entry-level and lighter-duty shells |
Tape width and pattern design
Common widths range from roughly 13 to 20 mm. Narrow tape handles tight curves but gives less margin; wide tape gives a more forgiving seal on straight seams. Pattern design matters: seams with sharp radii or bulky intersections lift tape and cause wrinkles. This is why we plan the tape map at pattern stage.
Common defects and checks
- Wrinkles or lifting edges: usually from tension, curvature or incorrect settings
- Gaps at intersections: tape ends not overlapped or cut correctly
- Adhesion failure: wrong tape for the laminate, contamination or poor settings
- Misalignment: tape off the stitch line leaves needle holes uncovered
Inspection and test steps are part of our quality control process. The construction page for this topic is seam-sealed construction, and the products that use it are in our hard shell jacket program.