The orb weavers are getting so fat on all the summer insects that their webs are sagging under the weight.
Eriophora biapicata is the most familiar large orb-weaver in southern Australia. This one has appropriated my clothes hoist as a frame for its web. Every night, the spider builds its beautiful trap. Then it dismantles the whole thing at dawn, consuming the silk as it goes. Spiders are thrifty. It takes an effort to manufacture that silk. It's not something to throw away.
In the wild, these spiders spent the day tucked up under a leaf but the nooks of the hoist provide a safer hiding place. I don't bother to close it up now because I'm worried about squashing the spiders. Not only does the Eriophora live here but also a few black house spiders and some other little fellows that I have yet to see in the ... er ... flesh. (Chitin?)
How stuff works has a delightful animation showing how a spider spins an orb web.