I asked similar questions after looking through all of the photos that Matthew Ross posted on Facebook. He lives in Japan and was kind enough to visit quite a few historical sites and take pictures and share them on the Daisho Facebook page.
I had a similar question about bamboo mats attached to the bottoms of houses. It was just to keep the rain from ruining the plaster. I suppose the nicer houses just had the lower portions made of wood so that it wouldn't be an issue.
I've included the conversation from Facebook, which has some more information. Mr. Ross also has posted a lot more pictures from different castles and temples on the Daisho page, so if your interested you may watnt to head over there and scroll down to the August posts.
Here's the link to the photos:
https://www.facebook.com/ma77h3nk3l/media_set?set=a.10153500665362594.1073741872.646922593&type=1&l=f718f784baJeffry Ryan Clarke: Wow, very informative, although it raises some questions. The rocks on the roofs of the houses were there just for weight to hold the roofs on? I noticed that some of the roofs were just lashed on. Was that the peasant way? And why the bamboo poles tied to the sides of buildings?
Craig Cartmell: Japan is subjected to typhoons every year. Thatched roofs don't do so well in 100mph winds.
Matthew Ross: The thatch roofs are rarely weighed... at least I've never seen one like that. The wood tiled roofs are weighed to avoid the wind blowing the shingles off. It's not a peasant thing, per se, you can see in the model that buildings in the manors also have stone weights, but not typically on the main house, which would have a more expensive roof: perhaps ceramic tile or a copper or lead skinned one.
The bamboo skirts on the lower edge of the wall is a protective feature, to avoid the stucco/plaster getting damaged by overly wet conditions. The bamboo screens between the shops work as a fence or hedge. The bundled poles seen in various places, often tied up under the eaves, are utility poles... used to dry clothes and laundry, and for various manufacturing tasks, and they are used with a series of ropes in winter to protect garden trees. The poles are lashed to the trunk, and ropes are suspended from it to help support the boughs from deformation by the weight of the snow. The effect is rather like a Christmas tree... I have a picture somewhere... I'll try to dig it out.
August 2