Waterproof Trousers

Waterproof trousers, the layer that decides how a wet day ends

Waterproof trousers come in two shapes. Some are a shell pulled on over whatever is already being worn, then taken off when the rain stops. Others are built as trousers in their own right, with a lining, pockets and a shaped leg, worn all day. The range covers both, plus the lighter pull-on rain trousers that live in a pack all summer, three-layer designs for sustained wet and cuts made for cycling.

Shell over the top, or trousers worn on their own?

A shell is lighter, packs into a pocket and comes off the moment the sky clears, which suits British weather that changes hourly, though it traps heat and rubs on a long descent. Worn-all-day waterproof trousers avoid that friction and fit properly, but cannot be removed when the sun arrives. If the walking is mostly dry with showers, the packable answer in waterproof overtrousers makes more sense; if the forecast is wet from the car park, a single garment is more comfortable. When a rucksack is on the back, a rain poncho covers body and pack in one piece, though it leaves the legs exposed in driven rain.

How do you get them on without removing your boots?

By the leg opening, the detail most often overlooked in the shop and most regretted on a hillside. A plain elasticated hem has to be forced over a muddy boot on one foot. A short ankle zip gets the boot through. A three-quarter or full-length side zip opens the leg completely, so the trousers go on standing up, over crampons or gaiters. Longer zips add weight and another seam to seal.

What should be checked before ordering a size?

• Waist adjustment: an elasticated back or side tabs cope with the bulk of the trousers worn underneath.
• Inside leg: too long and the hem gets trodden on; too short and rain runs into the boot.
• Seam sealing: taped seams inside are what stop water entering through the stitch holes at the seat and crotch.
• Venting: mesh-backed thigh vents or an open side zip release heat on a climb without exposing the leg.
• Cut over the knee: an articulated knee lets the leg bend without the whole trouser riding up the shin.

Why do they feel damp inside when nothing is leaking?

Because the water comes from the wearer. A waterproof layer slows the escape of sweat, and on a climb the body produces more moisture than any membrane moves out, so it condenses on the cool inner face. The fixes are behavioural: start cold, open the vents before the sweat starts, and drop a layer underneath. Quick-drying legwear such as hiking trousers underneath beats denim, which holds condensation against the skin.

How is the waterproofing kept working?

The face fabric is treated so water beads and rolls off. That treatment wears away at the seat, the thighs and anywhere a strap rubs, and once the outer soaks up water the trousers feel heavy and clammy though the membrane is intact. Wash with a technical cleaner rather than detergent, then reproof and warm the fabric gently to reactivate it. The same routine applies to trekking trousers with a weather-resistant finish.