Here are your two big starting questions for architecture:
1. What does the climate require?
2. What materials are available?
Homes created in the tropical heat in a rain forest are not going to be at all the same as homes created in colder locations, not to mention the arctic. You can see these kinds of differences in architecture around us all the time. American homes typically don't use stone - they will build a wooden frame, then put the windows in, and close the walls up last. English and French homes will start with brick or stone and do the windows last. There are also distinctions within the US, as you will seldom see brick or stone in California - they tend to have trouble with earthquakes, either requiring special reinforcement, or not lasting that long! New Mexico is typified by adobe and wood dwellings. If you build with wood in England, it rots unless you can protect it, which is why the wattle-and-daub technique was employed when wood was used in construction.
I mentioned how I had been to Himeji Castle in Japan this summer and had seen some of the restoration efforts there. One of the things that made it most interesting was how they had set up all kinds of videos to explain how the reconstruction was taking place. The roof featured layers of wood tied over with rope, then tiled, then plastered in a very particular way with white plaster. The architecture of the castle as a whole is in spiral formation with gates to bar the way, and plentiful slots for archers to shoot, which shows what kind of attacks they were expecting: army attacks without major siege engines or heavy artillery. European castles will have the portcullis, or trapping people between two gates method to achieve similar results. Moats are common to both styles of castle, but the Japanese castles are more decorative, while the English ones are more forbidding. Japanese castle-builders were thinking about battering rams, but not trebuchets.
You should also consider the cultural context of any castle's construction, and the intent of the builders. The cathedral of Albi, for example, was built to look imposing after a conquest, to symbolize power and victory over the Cathars.
Population density has a big influence on architecture at all levels, from the size of buildings and the density of their spacing, to the design of rooms and their uses. Americans have an unusual expectation of having a lot of space, which influences both land use and the design of homes. Cities will tend to build upwards, having many more people to house. Sometimes, buildings will be designed vertically more for fashion or aesthetic purposes than for functional ones.
I encountered an architectural challenge in my writing when I was drafting "Cold Words." I had put in a sort of generic entry hall, and my illustrious friend Tom Ligon encouraged me to think it through more thoroughly, so I asked myself what kind of entry architecture would be used by a species with a strong sense of smell. I turned it into the "confronting room" where there would be slots in the door between it and the inner areas of the house, to allow folk in the home to identify visitors and prepare either to welcome them or to fight them.
Ask yourself also why people build doors. How many doors do they build in a building? What is the expectation for behavior surrounding different kinds of doors - front doors, bathroom doors, doors at the bottom of the stairs, etc.?
Glenda asked whether the culture had nuclear families. Family structure is another really strong factor influencing architecture. Do people live in large family suites? In common halls? In round rooms that will keep in the body heat of those present? What is the expectation of privacy? Do families even live in buildings? Brian brought up the native American Indian dwellings of Mesa Verde and the surrounding area, and mentioned that a lot of spaces were used ceremonially or for storage, less so for family homes (he specifically mentioned Chaco canyon). Family might have different structure or meaning, and there might be no expectation of private individual space defensible by individuals.
Are rooms built with corners? How does this change expectations for the use of the space? This is a question that links back to building materials, as certain kinds of materials lend themselves more easily to straight lines, and others do not. Igloos are most effective when they take dome shape. Large stone bricks are rectangular, and tend to lead to rectangular buildings. Cut wood also tends to lead to rectangles. Lighter, thinner material works best with circles. Brian suggested that a people's spacial and geometric thinking will tend to be defined by their architecture rather than the other way around.
I mentioned C.J. Cherryh's book Wave Without a Shore, which featured interesting architecture because she specified early on that this was a colony in early stages where they had been provided with ultimately regular-shaped building materials and hadn't run out yet. This led to a lot of uniformity of structures and also of thinking.
Brian mentioned how Japanese rooms are still often measured in number of tatami mats - 8 mat room, for example (drawing) or 12.5 mat room (image).
Richard Adams' book Watership Down gave a surprising amount of attention to architecture, in particular talking about the role of tree roots in creating burrows, and having a rabbit warren where the proximity of man had influenced their thinking about how to burrow and design the warren. Practicality also came into the planning, which was discussed in great detail.
Glenda mentioned a documentary she saw featuring a Scottish geologist who discussed how architecture was influenced by the type of rock available in each area. Egypt had sandstone and limestone, which had great strength for stacking but wasn't as strong in creating open areas. Once you got to Greece's granite and Rome's marble, those had better strength for creating different kinds of spaces.
Brian also mentioned monuments. Lots of societies have monuments! What would your people do if they wanted to create something big and impressive? He mentioned that in Ecuador, Peru, and Bolivia, there are pyramids and ceremonial earthen platforms still being discovered that covered hundreds of acres. The only limitation is the materials. With stone, you can build obelisks and pyramids, but with earth you can still build pretty amazing things so long as you have the required manpower. So when you are designing a society, stick something amazing in there!
Make sure to think through whether things are actively being constructed. Large stone buildings have tended to be built over generations, but it's less common in literature to see things in the process of being built. Often, people began building and then learned how as they went along, with no overall plan. There would be scaffolding, and walls would be built, expanded, etc. Remember that architecture is dynamic rather than static (I'm always wanting to remodel my house!). Buildings also die, and one of the big causes of ruins is scavenging of the building material to use in other buildings. There should also be variation between old buildings and new, unless there is some specific destructive event that would remove old constructions from the picture. Cultural and social change is also reflected in architecture. History has a huge influence on how things are built and how they are destroyed. As Brian noted, Venice ran out of room in 1550, while Paris is a planned city that has been maintained with a core of 18th century architecture surrounded by 20th and 21st century architecture (La Défense, for example). The Champs-Élysées thus becomes a sort of walk through history. There are some buildings, like the Eiffel Tower and the Tour Montparnasse, which are infamous before they become famous.
I hope this has given you a lot of ideas for exploring architecture in your work. Thanks again to Glenda and Brian for attending! Today's hangout will be Dialects. I hope to see you there!