Wetsuit Seams Explained: Flatlock, Blindstitch, Taped and Liquid Sealed

Seams are the most important part of a wetsuit and the least understood. They decide how much water gets in, how much the suit stretches, what it costs, and where it will eventually fail.

They also cause more repair jobs than every other fault combined, which is why we have opinions about them.

Why seams matter more than thickness

Panels of neoprene do not leak. Joins do.

A 4/3 with poor seams will be colder than a well built 3/2, because every join that lets water through defeats the thin warm layer the suit is trying to hold against your skin. Thickness is what people compare in the shop. Seams are what they feel in the water.

The four constructions

Flatlock

The stitch goes all the way through both panels and lies flat, producing a wide visible stitch line that looks like railway tracks on both sides.

Strengths. Strong, flexible, comfortable against skin, cheap to produce. It does not create a raised ridge that rubs.

Weakness. It is a row of holes straight through the neoprene. Water comes through, by design.

Where you find it. Summer suits, springsuits, entry level 2mm gear, and hire fleets. Above about 20 degrees, a flatlock suit is fine and often more comfortable.

Repairability. Excellent. Straightforward to restitch.

Blindstitch, also called glued and blindstitched

Panels are glued edge to edge, then stitched with a curved needle that penetrates only part way through the neoprene and never comes out the other side. No holes right through the material.

Strengths. Substantially warmer than flatlock. The glue does the sealing and the thread does the holding.

Weakness. The glue line is the waterproofing, and glue eventually fatigues. This is the construction that produces most of the split seams we see, usually where stress concentrates at underarms, crotch and shoulders.

Where you find it. The default on almost every 3/2 and 4/3 sold in Australia.

Repairability. Very good. Cleaned, reglued and restitched, a rebuilt seam often outlasts the original.

Taped, either spot taped or fully taped

Blindstitched seams with a strip of neoprene or synthetic tape bonded over the join on the inside. Spot taped means tape only at high stress points. Fully taped means the whole seam.

Strengths. Adds a second seal and reinforces the join. Noticeably warmer and considerably more durable.

Weakness. Slightly stiffer. Tape can lift at the edges over time, and lifted tape is the early warning that the seam beneath is about to go.

Where you find it. Mid range and above, and on most winter suits.

Repairability. Good. Tape can be lifted, the seam rebuilt and new tape bonded over.

Liquid sealed, also called liquid taped or welded

A bead of flexible urethane or silicone based liquid rubber applied over the seam and cured, usually on the outside and sometimes both sides.

Strengths. The warmest and most watertight construction available. Stretchier than tape. It is what you want in cold water.

Weakness. Expensive. It cracks with age, particularly if the suit has been dried in the sun, and once it cracks the seam underneath is exposed. Cracking liquid seal is one of the most common faults on premium suits at the four year mark.

Where you find it. Top tier winter suits.

Repairability. Good, with the right materials. Cracked seal gets cleaned back and reapplied.

What to buy for Victorian water

Water on the Surf Coast sits around 13 degrees in August and around 18 to 19 degrees in February. That is genuine cold water for a good part of the year.

For year round surfing here, blindstitched with at least spot taping is the sensible minimum. Fully taped or liquid sealed is worth the money if you surf through winter regularly. Flatlock is a summer only proposition.

Where seams fail, and why

The failure points are the same across every brand, because they are stress points rather than manufacturing faults.

Underarms. Every paddle stroke loads this seam. Most common failure on our bench.

Crotch and inner thigh. Loaded on every duck dive and every time you stand up on the board.

Shoulders. Loaded getting the suit on and off, which is the most violent thing that happens to a wetsuit.

Ankles and wrists. Loaded every time the suit goes on, and the panels there are small with short seam runs and no room to distribute stress.

How to make seams last

Get in and out of the suit gently, taking handfuls rather than pinching, because pulling hard against a seam is what fatigues the glue.

Rinse in cool fresh water every session. Salt crystals work into the stitch line and cut at the glue as they dry. Never use hot water, which softens seam adhesive directly.

Dry in shade. UV degrades both the neoprene and the seam sealer, and cracked liquid seal is almost always a sun drying problem.

Fix small seam damage immediately. A two centimetre lift in tape becomes a fifteen centimetre split within a handful of sessions, because you stretch that exact point every time you put the suit on. A small repair is cheap. A blown seam running the length of an arm is not.

The bit that matters

None of these constructions fail because the suit is old. They fail because of stress at specific points, on suits that are otherwise perfectly good.

That is why seam repair is the best value job in the shop. The rest of the suit still has years in it, and the fault is twenty centimetres long.