Peru has a whole range of building construction styles, from the ancient to the modern. The ruins had three main types:
1. The finely made stone buildings which had the entire walls made of stone, and covered with wooden and thatch roofs (common at Machu Picchu and other ceremonial sites) with varying degrees of quality stonework. These often included stone pegs extending from the walls and carved stone rings to tie down and support the roofing rafters.
2. Some buildings included stone foundations, but the upper walls were made of adobe, with wooden and thatched roofs over the adobe. The adobe is prone to erosion and dissolution when rained on, so many of these ruins that aren’t well covered aren’t well preserved, or have required restoration since older times.
3. Others are made entirely of adobe, and are either covered with wooden, thatch, or tile roofs, to keep the rain from dissolving them. Those without any rain protection slowly dissolve back into dirt. The most common to see are adobe walls, with their conditions depending on how well they are protected from the rain.
Then of course there is the interesting historical mix in which Spanish churches were built on the top of the Inca palaces, using the fine Inca stonework as a foundation, but replacing the building on top with a colonial church.
Modern building construction can include an interesting mix or reflection of these older styles of Inca construction. The most common and simplest modern method used is the ubiquitous steel and concrete framing with brick walls. These buildings are sometimes covered with a smooth layer of stucco then to make them appear nicer, while others are left raw, showing the concrete skeleton and the brick wall. These tend to look seismically unsafe and you can almost imagine what the rubble pile would look like if there was a large earthquake: a mix of brick and crumbled concrete with strands of iron re-bar protruding from the wreckage.
We saw some interesting current adobe homes under construction, often two stories tall with eucalyptus beams providing support for the second floor and roof. Eucalyptus trees were introduced to the Andes in Peru in the last 100 years, for better or worse. They can often been seen on the otherwise mostly treeless slopes, often planted for either erosion control or for timber production, and they are now a mainstay in house construction.
Some of these modern homes use wooden beams to mimic the trapezoidal doorways and windows common in the Inca ceremonial stone buildings, and then they have begun using cement to fake the Inca fitted stone foundations, similar to how developers in the United States use fake stone work (tuscan stone, brick, etc.) as a lower band (wainscoat) to mimic traditional construction techniques of using stonework as a foundation.