A bit of history on the shade structure recently lost.
Built in about 1996. It attached securely to the 6,000 lb 20′ container. The foundation was with 4 by 6 columns bolted via brackets to railway ties sunk (dug) into the dirt. There was no concrete slab yet.
5 years later in about 2001 a slab, the one we see was poured. A frame of a couple sq ft was placed around each column base to keep the column open with followup temporary mini slabs filling in around each column base poured the next day. The idea was to be able to jack hammer out this tiny amount of concrete to inspect or repair column bases. But it also put the lowest 5″ of the column below grade and sealed trapping water. Not good in hindsight. And I don’t think any attention was ever given to inspection the column bases for rot. Our bad.
Then 13 years later in about 2014, a metal roof was added. Prior, it was 2 by 6 decking with 1/2″ gaps. It allowed the roof to breath but the metal roof not only added nice protection for the pilots from rain, it increased lifting forces during Santa Ana’s.
It is possible however that the metal roof added negligible lift.
It is also possible that the column bases might have actually been compromised for years since we had no easy way to inspect the column bases.
Regarding fire, it is obvious that wood burns more readily than metal. However there is a fairly good fire break around structure location. In Oct 2003 the “Old” fire burned all around the LZ. The house 800′ NW of the LZ was lost. The upwind hang glider storage container heated to the point of melting several gliders inside. The entire water infrastructure was lost and needed to be rebuilt. The shade structure (wood) had no damage. Go figure. Perhaps the fire break was a factor.