Hardshell Jacket Guide: What to Look For

A hardshell worn as an outer layer over a down or synthetic mid-layer is the standard layering approach for outdoor use. The hardshell does not need to be warm; it needs to be waterproof, breathable and durable. Understanding this distinction is the most useful starting point for any hardshell buying decision. If you are looking for a jacket that does everything in one, a hardshell is not what you want.

The waterproof membrane is the functional heart of a hardshell. It is a thin film, typically expanded polytetrafluoroethylene (ePTFE) or polyurethane (PU), bonded to the face fabric. The membrane contains microscopic pores that are large enough to allow water vapour molecules to pass through from the inside (breathability) but small enough to prevent liquid water droplets from penetrating from the outside (waterproofing). How that membrane is constructed and bonded determines the jacket's durability, packability and performance profile.

Two-layer (2L) construction bonds the membrane to the outer face fabric only, with a separate hanging mesh liner protecting the membrane from abrasion on the inside. Softer and more comfortable next to insulation layers, but heavier and less durable under sustained abrasion. Common in casual and budget hardshells.

Two-and-a-half layer (2.5L) construction bonds the membrane to the outer fabric and replaces the inner liner with a printed or embossed pattern. Lightweight and packable, but less durable. Good for ultralight applications where weight is the primary constraint.

Three-layer (3L) construction bonds the membrane to both the outer face fabric and an inner face fabric, creating a single laminated construction. More durable, more structured, and better performance under the abrasion of rucksack straps, harnesses and sustained outdoor use.

The DWR (Durable Water Repellent) finish is a separate treatment applied to the outer face fabric that causes water to bead and run off rather than soaking into the fabric. DWR does not affect waterproofing - the membrane handles that - DWR is present to help with breathability. When the outer fabric saturates (a condition called 'wetting out'), it blocks the membrane's ability to transmit vapour outward, causing the jacket to feel clammy from the inside even though it is not leaking. Refreshing DWR regularly is essential maintenance: a warm tumble dry is often sufficient to reactivate it, although specialist spray-on treatments can also be used.

Face fabric weight, measured in denier (D), affects abrasion resistance. Lighter facefabrics (20D and below) save weight but are more susceptible to damage from crampon points, rock abrasion, pack straps and general use. Heavier face fabrics (40D–75D) add weight but significantly extend the jacket's working life. For example, at Jöttnar, the Grim jacket uses a 75D face fabric specifically for durability under all-mountain use.

Waterproofing is measured using a hydrostatic head test, measured in millimetres. A column of water is placed above a sample of fabric and the height of the column at the point at which water begins to pass through is recorded. The higher the number, the more waterproof the fabric under pressure.

For outdoor and mountain use in British or Alpine conditions, a minimum of 20,000mm is necessary. A caveat: hydrostatic head is a standardised lab test under static pressure, not a real-world performance guarantee. Seam sealing quality, DWR condition and construction all affect real-world performance as much as the membrane rating.

Breathability is measured in one of two ways. MVTR (Moisture Vapour Transmission Rate) is expressed in grams per square metre per 24 hours. Higher numbers mean more breathable. Above 15,000g/m²/24hr is considered highly breathable; above 20,000g/m²/24hr is excellent for sustained active use. RET (Resistance to Evaporative Transfer) works inversely and a lower number is better. Below 6 RET is very breathable; below 13 RET is acceptable for moderate activity. When comparing jackets, check which measurement is being used and compare like for like.

Why breathability matters as much as waterproofing: in sustained high-output activity such as climbing, ski touring, trekking and trail running in rain an insufficiently breathable jacket causes internal moisture to condense against the inner face fabric. The result is a jacket that is wet on the inside despite being waterproof on the outside. This reduces the insulating ability of any mid-layer worn beneath it, increases the risk of chilling when exertion stops, and significantly reduces comfort over a long day. For anyone spending time outdoors under effort, breathability is not a secondary consideration. It is as important as the waterproof rating.

The hood: the hood is the single most important feature on a mountain hardshell after the membrane itself. A poor hood is the primary failure point for weather protection in serious conditions as it gaps, collapses in wind, or restricts peripheral vision at the moment when awareness of the terrain matters most. Look for: helmet compatibility (the hood must fit over a climbing or ski helmet without restricting movement or vision); a wire peak or stiffened brim that maintains its shape in wind and prevents collapse over the face; full peripheral vision when the hood is cinched - you should be able to turn your head with the hood rotating with it; and single-hand adjustability so the hood can be tightened while wearing gloves. A hood that requires two hands and dexterity to adjust is not a mountain hood.

Seam sealing: all critical seams in a serious hardshell should be fully taped. Some budget hardshells use critically-sealed seams with only the most exposed seams being taped in order to reduce cost. In sustained rain, untaped seams will eventually allow water ingress at the needle holes. Full seam sealing is non-negotiable for us.

Pit zips: underarm ventilation zips allow rapid heat dumping during high-output activity without removing the jacket. Useful for ski touring, winter climbing approaches, and any activity with significant variation between exertion and rest. They are not universal and some lighter jackets omit them to save weight, which is a valid trade-off for fast-and-light applications - for example trail running.

Pockets: Jöttnar hardshells are designed so both hand and chest pockets remain accessible when wearing a harness or a rucksack hip belt. Internal pockets keep phones, maps and food dry.

Waterproof zippers: prevent water tracking along zip pulls - a premium detail that matters in sustained rain.

Hem and cuffs: adjustable hem and cuffs seal the jacket against wind and rain ingress. Internal elastic cuffs with velcro adjustment are more durable than velcro-only cuffs.

Hem: A drop hem at the back provides additional coverage when bending or reaching.

Weight considerations: A trail running shell can be as light as 250g and remain fully functional for its intended use. A fully featured hardshell with a proper helmet-compatible hood, full seam sealing, durable face fabric, velcro sealed cuffs, Recco avalanche transponder system, and pit zips will sit between 400g and 700g. That weight is there for a reason. If you're choosing a jacket for anything involving crampon points, rock, ice tools, and pack and general abrasion, the 250g option is not the right tool. The weight you save on the approach you may pay for on the mountain.

Getting the weight-durability balance right depends entirely on intended use. Trailrunning and fastpacking favour jackets under 200g - thin face fabrics, minimal features, packable to almost nothing. The trade-off is durability: these jackets are not designed to survive repeated abrasion from rock, ice, harnesses or pack straps. General hillwalking and trekking sits in the 300–500g range, balancing packability and durability. Technical mountaineering and alpine use requires 400–600g or above, prioritising durability and feature set. A jacket that fails in the mountains has a different cost than one that fails on a trail.

Hardshell vs softshell vs windshell: these are complementary categories, not competing ones, and a complete mountain wardrobe often includes all three. A hardshell is the definitive outer layer for sustained rain, snow and serious mountain weather - fully waterproof, fully seam-sealed, the primary weather barrier. A softshell is water-resistant but not waterproof. It offers more breathability and flexibility than a hardshell and excels in high-output activity in changeable but predominantly dry conditions: ski touring approaches, winter climbing on dry days, trekking in light drizzle. It is not a substitute for a hardshell in sustained rain. A windshell is windproof with minimal water resistance and maximum breathability - the right choice in dry, windy conditions, or sustained trail running where wind protection and ventilation are the primary requirements, not rain defence.

The practical question for any hardshell buying decision: what conditions is this jacket going to see, and what is the cost of it failing? For a typical mostly dry day's walk in the Brecon Beacons, ski-touring or downhill skiing in sunny conditions, a softshell may be entirely adequate. For a winter ascent in the Cairngorms, or an alpine route with the threat of poor weather, the specifications - membrane rating, breathability, face fabric denier, seam sealing, hood quality - all need to be at the top of the range. The mountain does not grade on a curve.

Quick reference on the key decisions. Construction: 3-layer for optimum performance. Waterproofing: 20,000mm+ for mountain use. Breathability: 15,000g MVTR or above for active use. Face fabric: 60D+ for technical use, lighter for trail and fastpacking. Seam sealing: full taping across all seams. Hood: helmet-compatible with wire peak and single-hand adjustment if helmets are worn. DWR: PFC-free chemistry as standard. Weight: matched to use case and not minimised at the expense of durability where durability matters.