Diane Rixon describes on DIY Life how to make any basic dog bed, which involves buying a large waterproof under-bed storage bag, stuffing it with old pillows or clothing and then sewing a cover with a zipper closure for the outside. Instructables provides details for how to make an elevated cot-type outdoor dog bed. A frame is constructed out of polyvinyl chloride pipe and an outdoor fabric stretched over it.
The fabric chosen for an outdoor dog bed needs to be resistant to water, sun, mildew and weather. Instructables suggests using marine upholstery fabric, which can be purchased cheaply as remainders or scraps from marine fabrication outlets. Sunbrella sells a wide selection of outdoor fabrics intended to be used for outdoor furniture cushions which work quite well for dog beds.
Commercial outdoor dog beds typically use a heavy nylon fabric called Cordura that comes in a waterproof form. Heavy vinyl is another option because water just puddles on it, and it wipes clean easily. It is also very resistant to dog claws. Alternatively, Kuranda dog beds sometimes uses a fabric with an open weave mesh on its commercial outdoor beds. Rather than being water-repellent or water-resistant, this fabric is designed to let water run right through it, so it rapidly dries out.