A know-how guide to buying outdoor cushions

Lawn furniture is made to last for years, but what about the cushions? Outdoor cushions must meet special needs, and not all cushion filler or cushion fabric is created equal. Before you buy new cushions for your lawn furniture, know what fabric and filler will keep them looking good for years, not just one season.

Waterproof is not necessarily a good thing in outdoor cushions. We assume that water does not penetrate waterproof fabric. However, unless the seams and zipper flaps are sealed on the inside, (as it is in high-quality rain clothing), water will penetrate. This moisture collects in the foam and becomes a breeding ground for mould and mildew.

The real trick is to use non-water-proof fabric and inner foam and foam wrap which are specifically designed for outdoor use--they let water pass through.

Look for foam that is designated "open cell," or specifically "outdoor."

• Open cell foam is firmer than the usual cushion foam. The holes are connected to each other, creating a path for water.
• "Dryfast" is a specific type of outdoor foam that resembles a mass of clear plastic string. It is very firm and much heavier than regular foam, so cushions made of Dryfast will not blow off the furniture easily.
• "Densified Polyester" resembles thick, very firm quilt batting about one-inch thick, and is very light weight and works well with Dryfast. Stack layers of Densified Polyester to get the right cushion thickness or sandwich Dryfast between the Densified Polyester to make the seat softer and increased its longevity.

The foam inside cushions is often wrapped with a quilt-batting-like product which softens square edges. This won't impede the water-transfer of your good foam unless it's glued to the foam, which prevents the water from passing.

Cotton thread will rot, so look for cushions using UV resistant, marine, or outdoor thread, as well as plastic zippers or buttons that won't rust.

Colour is applied to fabric by dyeing it after weaving, printing a design on the fabric, or by adding colour to the threads before weaving. This last process incorporates dye as part of the fibre and makes the resultant fabric resistant to fading and even bleachable. Fabric made from solution-dyed yarn makes long-lasting, fade resistant outdoor cushions.

The sun will rot natural fibres, sometimes after just one season. If your outdoor fabric is not UV-protected, you could consider a UV-protectant spray to reduce possible sun-fading.