If you read only one paragraph: water repellency is about a surface, waterproofness is about a barrier. A repellent finish makes droplets bead and roll off a fabric that still breathes. A waterproof construction resists water under pressure, usually because something has been laminated or coated onto it.
How each one is measured
| Water-repellent | Waterproof | |
|---|---|---|
| What it describes | Surface behaviour | Barrier performance |
| Typical standard | ISO 4920 or AATCC 22 spray test | ISO 811 hydrostatic head |
| Result format | ISO grades or an AATCC spray rating up to 100; not a percentage | A pressure in millimetres of water column |
| Breathable | Yes | Usually not |
| Survives cleaning | Only if tested after a defined care cycle | Depends on the coating, not the finish |
Why the care cycle matters more than the first number
A brand-new repellent finish will nearly always spray well. The meaningful question is what the rating is after the cleaning the customer will actually perform. A repellency claim published without a care condition attached is a claim about a fabric nobody will ever own for very long.
What a repellent finish does not do
- It does not stop water entering through seams, zips or the cushion's own construction.
- It does not make a cushion suitable for standing water. Repellency delays wetting, it does not prevent saturation.
- It does not prevent mildew. A wet cushion left unventilated will develop mildew regardless of the surface finish.
- It does not, on its own, resist oil-based staining such as sun cream.
Specifying honestly
For covered decorative outdoor upholstery, a repellent finish, a removable cover and ventilated storage can preserve hand, comfort and appearance more effectively than adding a waterproof laminate. Waterproof construction is better reserved for components designed to shed water, such as protective covers, canopies and cushion inners.
Where a project genuinely requires a waterproof backing, that is a separate development with its own SKU, its own price and its own test set. It changes the hand, the cost and the environmental profile of the cloth, so it should be a deliberate decision rather than an assumed feature.