Yeah, that's one of the things that has me completely baffled. Protection board is for keeping the waterproof membrane from getting punctured while back filling a foundation, but I don't see any signs of excavation around the perimeter anywhere. Nor would there really need to be unless there is a lot more seriously fucked with 14BLC than just the fire. While that's possible, I don't see the fire insurance claim covering it, and again, where's the excavation? Also that looks like the old kind from at least 10 years ago or more. Maybe it's left over from the remodel that was done in 1986, but I didn't think the work done then was that extensive.
I'm pretty certain they've recently been stripping the walls and floor out of the kitchen (at least), so you may be right that it is from that strange four season porch out the kitchen. From earlier pictures of the back of the greenhouse it's clear that that protection board wasn't there in April. Even though it's old, it's a fairly recent addition to that pile. Where did it come from? And what is it doing there? (And why hasn't it been tossed in the dumpster where it belongs along with the rest of that pile of Barbage?) That's probably all just more of the many Chandler Mysteries.
