Waterproof Hi Vis Clothing

Why Class 4 Matters – The 54% Difference

EN343:2019 rates waterproof workwear on two scales: waterproofness (Class 1-4) and breathability (Class 1-4). Class 4 waterproofness requires minimum 20,000mm hydrostatic head – that's the pressure of a 20-metre water column pressing down before fabric lets a drop through. Class 3 is rated to 13,000mm, Class 1 to just 8,000mm. The 54% jump from Class 3 to Class 4 (13,000mm vs 20,000mm) is the difference between seams leaking after three hours in moderate rain and staying bone-dry through an entire shift in a downpour.

Class 4 breathability (the second "4" in Class 4:4) measures moisture vapour permeability at 15,000g/m²/24hrs minimum. Without it, you stay dry from rain but get drenched from sweat. Microporous membranes have millions of holes – each 20,000 times smaller than a water droplet (rain can't get in) but 700 times larger than water vapour molecules (sweat escapes). That's why high visibility waterproof jackets with Class 4:4 certification work during physical tasks like highway repair or building site supervision.

Key Construction Details

Fully taped seams are non-negotiable. Every stitch creates a hole. Heat-sealed waterproof tape covers all stitching from inside the garment, sealing leak points completely. Storm flaps cover front zips – double protection against driving rain penetrating through zip teeth. Adjustable cuffs with hook-and-loop straps or elasticated inner cuffs seal wrists. High collars with chin guards stop rain running down your neck. Articulated hoods fit over hard hats and helmets, with peaked fronts directing water away from your face.

Care and Replacement

Wash waterproof hi vis jackets at 30-40°C maximum using technical wash products designed for waterproof fabrics – regular detergent clogs membrane pores. Never use fabric softener; it destroys waterproof coatings. Tumble dry on low heat to reactivate DWR (Durable Water Repellent) coating that makes water bead off the surface. When water stops beading and starts soaking into outer fabric ("wetting out"), apply spray-on or wash-in reproofing treatment. Replace garments after 200-300 washes, when seams leak even after reproofing, or when reflective tape cracks significantly.

Typical Applications

You need EN343 Class 4 waterproof hi vis clothing for highways maintenance and motorway roadworks in heavy rain, utilities work during storms, emergency breakdown and recovery services operating in all weather, railway trackside work through winter, building site management requiring outdoor presence, forestry and arboriculture during wet seasons, outdoor security in all conditions, agricultural work continuing through rain, waste collection through downpours, or any role requiring extended outdoor exposure in severe wet weather where standard Class 3 waterproofs won't keep you dry for full shifts. According to HSE guidance, "the darker the conditions or worksite, the greater the amount of HV clothing required" – Class 4 waterproof hi vis jackets with EN ISO 20471 Class 2 or 3 visibility meet both waterproofing and safety visibility requirements for the most demanding UK work environments.