Standard fabrics are in 100% Spun Polyester. The fabrics have a water resistant coating. They are not water proof, but will repel water in moderate quantities. However, if the cushions are left out-doors in heavy rain for more than one day the fabrics will start to absorb water.

Spun Polyester fabric
Spun Polyester 235g/m2. Color Grey BA-M072
Snow White Spun Polyester
Spun Polyester 230g/m2. Color: Snow White

To make the cushions as close to 100% waterproof as possible the cheapest way is to use waterproof inter-liner (inner fabric) and the Spun Polyester fabric with a water resistant treatment as shown on the Deck lounger below. Waterproof inter-liner is an optional extra.

Bamboo Deck Lounger