The primary building material in ancient and classical China was wood; walls could be covered by clay, earth, loam, plaster, etc. These are not the most durable materials, therefore very little has survived to the present day. (A similar problem exists elsewhere in the world, e.g. Etruscans or the Roman Republic, but that discussion belongs elsewhere.) Rooftiles were used too, at least in urban areas (though I highly doubt they're all of the shiny blue glazed variety 0 A.D.'s Han China mod structures currently have). Stone appears to be mostly used for sculpture.
What has survived from the Han period are hundreds of tombs near the capital, some very well-preserved, including, amongst other things, texts (yay!), paintings, and terracotta miniature models of buildings. Some examples:
well:
pottery:
stove:
kitchen:
rice paddy:
goat/sheep pens:
pig sties/toilets:
mill (and bakery?):
granaries:
houses:
towers:
fort:
manor/palace:
Note the bilateral symmetry (i.e. left mirrors the right).
(All images are from Wikimedia Commons: https://commons.wikimedia.org/wiki/Category:Ceramics_of_the_Han_Dynasty_-_Models_of_buildings )