I have been in and out of the hobby since 1972. There have been club and home layouts as well as periods of inactivity driven by career circumstances. When we moved to Arizona, I was put off by the lack of basement homes aside from the real expensive properties typically in northern Scottsdale.
Bless her heart, my wife (who bought the first Tyco train set as my present for our first Christmas in '72) said why not an outside layout? A brief head-slap moment later, I was off and running. First, get rid of the fruit trees in the side yard (rattle snakes were tending to treat this area as their personal sanctuary from the summer sun) and relocated the lawn building (I don't need no stinking lawn building!).
Our home is located in the Sonoran desert so wet weather is the exception- mainly during the months of July and August (when it's too hot to be anywhere but in the pool), and maybe a few scattered showers during December and January.
Bingo, we have a 56 ft long by 10 ft wide train room with a blue sky ceiling and plenty of natural light.
Brackets anchor the frame to the concrete block wall between houses that is typical in Phoenix . Simple and effective as the load is vertical, static, and minimal. I used 2 connectors per 8 foot section and by screwing each section together, created a strong frame network.
Simple wall anchors into the concrete block wall used to divide yards in Phoenix. The load is minimal and static.

Preassembled sections attach to the wall via the anchors.

I started with the upper level and worked to the ends. In the process I purchased higher quality and more powerful battery powered tools before constructing the end sections.
After making the end pieces, it was obvious they were far superior in fit and finish, to the original center units, I disassembled the mounted center units and reconstructed them to tighter tolerances with better lumber.
Attaching of the "new" upper center sections.
