Patio chairs with metal frames should last a long time. But the webbing wears out eventually. Since the metal frames often last much longer than the webbing, you can give your old lawn chairs new life by replacing the webbing.
There are two types of webbing straps used for patio chairs. One is made of woven polypropylene material that is often made in stripes of more than one colour. These strips weave above and beneath each other to provide a sturdy and comfortable seat. The other kind is made of shiny vinyl in bright solid colours. This usually stretches across the chair from side to side. Since the vinyl is stronger than the polypropylene, there is no need for a woven look.
The polypropylene webbing can be attached to the chair by two kinds of hardware. One is called webbing clips, wide metal clips with teeth that grab onto the strap and a tab that fits into a slot on the chair's frame. The other kind is a screw. Fold the corners of the end of the strap over to form a triangular shape so the screw goes through more than one layer of the strap material for extra strength. Vinyl straps attach to the frame with screws only.
Vinyl straps are often narrower than the polypropylene kind. They don't breathe as well as the polypropylene material. The polypropylene kind needs to be folded into a triangle shape if being attached to the chair with screws.
Vinyl straps are stiff. To stretch and bend them, soak them in warm water before attaching them to the chair's frame. The warm water will make them more pliable.
When working with webbing that weaves over and under in both directions, attach the top-to-bottom straps first. After attaching each strap, check to be sure there is enough slack in the strap to allow the chair to fold. You need this slack for each of the strips that run from the top of the chair to the bottom. Also, each of these straps must go behind the horizontal metal bar at the fold of the chair.