Väderklass
What W1 to W4 mean, and everything they do not mean.
This is the reference page for every figure printed elsewhere on this site: how the water column is measured, why the seam matters more than the number, what condensation does under a sealed cover, and why only 2 of our 43 items carry a UPF value.
The four classes
A class is a range of water column values plus a set of construction decisions that usually come with it. It is a shorthand, not a specification: the individual figures on each product page are the specification.
W1 — Dust and dew
Keeps dust, pollen and overnight condensation off something that is already under a roof. It is not a rain cover and we do not sell it as one.
- Typical water column
- 500-800 mm
- Items in this class
- 11
- Browse
- See W1
Suited for
Indoor storage, garages, barns, short-term covering between uses.
Not suited for
Anything left in the open through a rainy week.
W2 — Rain, one season outdoors
Sheds rain over a summer season outdoors. Seams on most W2 items are stitched and not taped, which means the seam is the first place water gets through.
- Typical water column
- 1,500-2,000 mm
- Items in this class
- 11
- Browse
- See W2
Suited for
Spring to autumn outdoors, inland, on something you move or check regularly.
Not suited for
Winter, coastal salt, or being left untouched for months.
W3 — All year outdoors
Built to stay outdoors through a full year including winter. Taped seams and vents on most items in this class, because a cover that stays on for months has to let condensation out.
- Typical water column
- 3,000-5,000 mm
- Items in this class
- 17
- Browse
- See W3
Suited for
Year-round outdoor use inland, including snow load on a supported frame.
Not suited for
Constant salt spray and very high sun hours over several years.
W4 — Long exposure and salt
The heaviest fabric we carry, for salt air, high sun hours and long periods where nobody takes the cover off. Taped or welded seams, reinforced corners, vents.
- Typical water column
- 5,000 mm and above
- Items in this class
- 4
- Browse
- See W4
Suited for
Coastal moorings, long-term outdoor storage, high UV regions.
Not suited for
Nothing we sell survives being left slack on a sharp edge. Fit still matters more than class.
These classes describe what the fabric was tested to. They are not a promise about your weather.
Water column, and where it stops being useful
Hydrostatic head is measured by standing a column of water on a clamped piece of fabric and raising it until three drops appear on the other side. The height of that column, in millimetres, is the figure. We use EN 20811 or an equivalent method, and we measure on the fabric, away from any seam.
It is the only meaningful number for water resistance, and it is also the number people most often over-read. A 5,000 mm fabric with open needle holes through it leaks at the seam long before the fabric is troubled. That is why every product page here puts the seam treatment directly next to the water column.
Because we publish the figure, you can check it. That is deliberate. It also means we have to be right, which is a discipline we would rather have than not.
What we will never write
You will not find absolute water claims anywhere on this site: no percentage figures, no promise that a seam holds forever, no assurance that whatever is underneath stays dry. That is not a style choice. Claims of that kind describe a product which does not exist, and we could not stand behind one if you put it on a test rig.
Seams: the part that decides it
Every needle hole is an opening in a coating that was continuous before the machine went through it. Under sustained rain, water finds those holes before it finds the fabric.
Taped (14 items)
A strip of heat-applied tape seals the underside of the stitch line. The tape is the part that ages first and it can lift after several seasons of flexing.
Stitched, untaped
No tape. The needle holes are open. On the pages of items built this way, we say so in exactly those words. It is not a defect, it is a construction choice with a consequence, and the consequence belongs on the page.
Welded
The two faces are fused. No thread, no holes. Welded seams are stiff, and a hard crease folded repeatedly in the same place is where they eventually fail.
Vents, and the water that was never rain
A fully waterproof cover with no ventilation traps condensation underneath. That water comes from the air inside, not from rain. Vents let it out. The covers with vents are marked.
27 of the 43 items here have vents. The ones that do not carry a note on their page saying what that costs you. If a cover is going to stay fastened for months, the vents matter more than the last thousand millimetres of water column.
UV: what a lamp can tell you, and what it cannot
Ultraviolet light is the main reason outdoor fabric stops working. It breaks down the coating and the yarn, and it does it at a rate that depends on your latitude, your sun hours, your salt and how often the fabric is washed. None of those are things we know.
What we can give you is a standardised comparison: hours under a xenon lamp and a grade on the blue wool scale. 21 of our items have been through that test and print the result. 22 have not, and their pages say not tested rather than leaving the field blank.
Only the items with a test report carry a UPF number. The others block light, but we haven’t measured how much UV. A UPF figure requires EN 13758-2 or AS/NZS 4399, and without one we print nothing.
We will not convert any of this into a number of seasons. Anyone who does is guessing on your behalf.
None of this is safety equipment
This is a cover. It is not safety equipment, and it will not hold a boat in place. Check your mooring and your straps separately.
We do not make or sell life jackets, buoyancy aids, throw lines or any vessel safety gear. Those are regulated products that require certification, we hold none, and nothing on this site should be read as a substitute for one. We reference no safety approval and no protective-equipment certification anywhere, because none applies to a cover.
A cover does not secure a boat. Mooring lines, cleats and straps do that, and they are checked separately from anything you buy here.
The dry bag, specifically
Our roll-top dry bag keeps rain and spray off gear on board. It is not diving equipment, it is not tested for submersion, and it is not a flotation aid. It also only works if you roll it properly.
And the grill cover
Let the grill cool completely before covering. Fabric near a hot surface is a fire risk. Our grill cover has no flame-retardant treatment and it is not tested against one.
How to measure
Measure before you order. A cover that is too tight tears at the corners, and one that is too loose flogs in the wind and wears itself out.
- 01Measure the object, not the old cover. An old cover has stretched, and copying it repeats the fit you already have.
- 02Length runs along the longest side. Width is taken at the widest point, including anything permanently attached that sticks out.
- 03Height goes from the ground, or the deck, to the highest fixed part. Fold down anything that folds down first.
- 04Add nothing for slack. Every pattern here already includes it, and extra slack is what flogs in the wind.
- 05If you are between two sizes, send us the numbers. We would rather answer an email than process a bulky return.
Wear, or a fault?
Outdoor fabric changes with use, and not every change is a defect. Here is how we draw the line, in advance, so it is not a matter of argument afterwards. The same table is on Reklamation.
| What happened | How we treat it |
|---|---|
| Colour lightened after long sun exposure | Wear. UV degradation is an inherent property of the material. |
| The coating gradually stopped working over several seasons | Wear. |
| The coating peeled or the fabric went brittle within the first season | Fault. |
| Measured water column is below the figure we published | Fault. We publish the number, so it can be checked directly. |
| Seams opened, a drawcord broke, a buckle came off | Fault. |
| Dimensions do not match what the page said | Fault. |
| It tore in strong wind because it was not fastened at every point | Judged case by case. The page says it has to be fastened at every point. |
You can report a fault for three years from delivery. For the first two years, if something is wrong, we have to show it wasn’t faulty when you got it. Not the other way round.