I always wondered why the porch was in such poor shape. It originally had one inch redwood decking, but even that had gone bad. Everything was in a deplorable state. But after doing some research I think I came across why and it would seem prudent to pass that along to anyone with a porch, if you will indulge me.
At some point, some resourceful individual decided that the old open lattice work between the porch piers should be filled in with cement block. Only the far end was left open, presumably for access. However, in doing so, the owners violated the prime directive in porches–they must breathe. All of the moisture in the ground and air accumulated in that enclosed space and dramatically shortened the life of the porch.
Be sure to adequately ventilate your porch cavity! Check out sites that provide the details on proper ventilation depending upon your type of porch.