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Waterproof garments explained

It's often the case when looking for a new outdoor jacket that we buy a water repellent/showerproof version when in fact what we really want and need is a fully waterproof jacket. Often, the difference is not explained by retailers so I thought I’d try to explain the difference.

There are four main factors that determine whether a jacket is fully waterproof:

The fabric

A waterproof membrane is a thin lining which is bonded to the back of a fabric to stop water penetrating it.  The membrane allows perspiration to pass through one side but not the other, so moisture is wicked away from the body, but the rain can’t get through.  

To check the performance level of the fabric and assess how waterproof it is, the outdoor industry uses a Hydrostatic head rating.  A Hydrostatic head test measures how tall a column of water the fabric can hold before water starts to seep through the fabric. The higher the hydrostatic head value the more water resistant a fabric is and the more water pressure it can withstand before it leaks.

According to British Standards, any fabric over 1,500mm can be classed as waterproof.  At Rockholly we want to go beyond that and ensure you are going to stay dry for longer, so any fabric we use will have a minimum rating of 8,000mm. This means a fabric with a water column of 8,000mm is able to withstand the same level of pressure as if there were 8 meters of water pushing down onto your head & coat. That’s a lot of rain!




 0 – 1,500mm

Water resistant / Snowproof

Very light rain

 1,500mm – 5,000mm


Light to average rain

 5,000mm – 10,000mm

Very Waterproof

Moderate to heavy rain



The Seams

For a coat to be 100% waterproof, it must have taped seams.  A coat can have a membrane bonded lining and a water-repellent coating, but if it's not taped the water will get through the seam stitching.  A hot-melt tape is applied to all jacket seams to ensure water can’t escape through the holes created by sewing a coat together.  You won’t see the tape as it will be hidden inside the lining, but you will notice it if you check the seam of the jacket (it is a soft tape of around 1cm width).  

The waterproof coating (DWR)

Waterproof coats have a Durable Water Repellent chemical (DWR) applied to the outside of them (you will have seen water beading on a waterproof coat and running off the fabric, rather than soaking into it). We use an environmentally friendly PFC free DWR at Rockholly, more of which you can find out about by clicking here.

The Design

Features such as storm flaps (the material that covers the front zip), hoods that adjust well around your face and cuffs that can be cinched in, all help to contribute to keeping the rain out.



Breathability explained

Breathability in a waterproof fabric allows perspiration to escape, which is especially important if you are doing anything active. If a waterproof jacket is not breathable the perspiration will build up inside the coat leaving you feeling uncomfortable, damp and often thinking that your waterproof coat has leaked!

2 Layer jackets

Our SS18 transitional jackets are 2 layer waterproof jackets. 2 layer waterproof jackets are made up of a waterproof outer shell and an internal lining. The lining prevents the deterioration of the inner membrane from your body’s movement and perspiration. The polyester lining (as opposed to a cotton lining) help to aid the jacket's breathability.

Why buy a waterproof jacket as opposed to a water-resistant jacket?

Most water-resistant jackets, won’t have some of the features we have explained above. Seams may not be taped and fabrics are unlikely to be bonded. Water-resistant coats might withstand a light shower but would struggle in heavy rain.

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