How to choose overtrousers

Waterproof ratings (hydrostatic head)

Most makers quote waterproofing as a hydrostatic head in millimetres. In the test, a column of water is stood on the fabric and its height is increased until water pushes through. A 10,000mm rating means the fabric held back a 10-metre column of water before it leaked.

That sounds like overkill for rain, but pressure on your trousers is far higher than a gentle shower suggests. Kneeling on wet grass, sitting on a soaked rock or a bike saddle, and the flex at the knees all concentrate pressure, and fabric loses some performance as it wears. Legs and seats take more of a battering than shoulders.

Treat these bands as a rough guide, not a rule. Test methods vary, and a high number on the fabric is worthless if the seams leak. Look for "fully taped" or "sealed" seams; "critically taped" usually means only some seams are sealed. Coated PVC or PU work trousers are often welded rather than stitched, which is also fully waterproof.

For work wear, the European standard EN 343 rates garments (seams included) for water penetration and breathability in classes. See our work & hi-vis guide for more.

Breathability

Your legs produce sweat and water vapour, especially walking uphill or pedalling. A breathable fabric lets some of that vapour escape, so you are less likely to get damp from the inside. No waterproof fabric breathes as well as ordinary trousers, and none can keep up with you at full effort, so ventilation zips and taking them off when the rain stops still matter.

You will see two kinds of figure:

• MVTR (moisture vapour transmission rate), in grams per square metre per 24 hours. Higher is more breathable. Figures in the tens of thousands are common on technical fabrics.
• RET (resistance to evaporative heat transfer). Lower is more breathable. As a loose guide, single-digit RET figures are usually described as very breathable, and figures above about 20 as not very breathable.

Different labs and methods produce different numbers, so compare figures within one brand's range rather than across brands. And ask yourself honestly whether you need it: if you are mostly standing or sitting, a tougher, less breathable fabric may serve you better and cost less.

2, 2.5 and 3-layer fabrics

Every waterproof-breathable fabric has a face fabric (the outside) and a waterproof membrane or coating. What differs is how the inside is protected.

• 2-layer: the membrane is bonded to the face fabric, and a separate loose mesh or taffeta lining hangs inside to protect it. Comfortable against skin, a little bulkier, and common in everyday and budget overtrousers.
• 2.5-layer: instead of a lining, a thin protective print or film is applied over the membrane. Light and very packable, which is why it is popular for emergency and lightweight trousers. It can feel clammy against bare skin and is usually less hard-wearing.
• 3-layer: a thin inner fabric is bonded to the membrane, sandwiching it. Typically the most durable and best-performing construction for heavy use, and often the most expensive.

Heavy PVC and PU-coated trousers, common in farming and site work, sit outside this system: they are fully waterproof and very tough but barely breathable. Great for standing in a slurry yard, miserable for walking up a hill.

Full-length vs 3/4 side zips

Side zips are the single biggest usability feature on overtrousers.

• No zips or short ankle zips: lightest and cheapest, fewest leak points, but you will usually need to take your boots off to get them on. Fine for packable spares you rarely wear.
• 3/4 zips (roughly ankle to knee or thigh): a good compromise. Usually enough to get on over walking boots, and they let you vent heat from the lower leg.
• Full-length zips (ankle to hip): you can put them on or take them off standing up, boots and crampons and all, and even open them fully to use as wide ventilation. The cost is a bit of weight and a longer zip to look after.

Check the zips have a storm flap or are water-resistant, and that there is a popper or tab at the top so they cannot creep open. Two-way zips let you vent from the top while keeping the ankle closed.

Fit over boots

Look at the ankle opening and the length of the zip together. Chunky walking boots, safety boots and especially wellies need a wide cuff. Overtrousers should sit over the top of boots and wellies, not tucked in: if you tuck them in, rain runs straight down your leg into your socks. An adjustable ankle (poppers, Velcro or a drawcord) lets you cinch them down once they are on, so they don't flap or catch on crampons, chains or brambles. Our sizing guide covers length in detail.

Packability and weight

If overtrousers live in your rucksack, pannier or glovebox most of the time, weight and packed size matter more than ultimate toughness. Lightweight 2.5-layer trousers can pack down very small. The trade-off is durability: thin fabrics abrade faster when you sit or kneel on rock, and the short or absent zips make them fiddlier to get on. If you wear them all day, every day, go heavier.

DWR and reproofing

Almost all waterproof-breathable fabrics have a durable water repellent (DWR) finish on the outside, which makes rain bead up and roll off. It is not what keeps you dry (the membrane does that), but it matters: when the DWR wears off, the face fabric soaks up water ("wets out"). The trousers are still waterproof, but they feel cold and clammy, stop breathing properly, and many people assume they are leaking.

DWR wears fastest where you sit, kneel and where the legs rub. Washing with a technical cleaner and reapplying DWR restores it. Full steps are in our care & reproofing guide.

PFC-free treatments

Traditional DWR finishes used fluorinated chemicals (PFCs, part of the wider PFAS family) that are extremely persistent in the environment. The outdoor industry has been moving to PFC-free or PFAS-free DWR, sometimes labelled "C0", and regulators are tightening rules on these chemicals.

PFC-free DWR works, but in general it is more easily defeated by oils and dirt, so it benefits from more regular washing and reproofing. If you choose PFC-free trousers, choose a PFC-free reproofer too. Some brands also offer membranes that avoid fluorinated materials entirely; check the product description if that matters to you.

Other details worth checking

• Waist: elasticated with a drawcord is standard. A button or popper fly helps if you wear them all day. Bib-and-brace styles stop the rain getting in at the back when you bend.
• Reinforcement: tougher panels at knees, seat and inner ankles (where boots and crampons scuff) add years of life.
• Articulated knees and a gusseted crotch: make climbing stiles, getting on a bike or kneeling far more comfortable.
• Pocket access: "pass-through" slits let you reach the pockets of the trousers underneath.
• Leg lengths: short, regular and long lengths are a big plus if you are not average height. See the sizing guide.
• Colour and visibility: dark colours hide mud; bright colours and reflective trim help you be seen on roads and at work.
• Women's cuts: worth seeking out if unisex trousers are baggy in the leg or tight at the hip.