Inca buildings were made out of fieldstones or semi-worked stone blocks set in mortar; adobe walls were also quite common, usually laid over stone foundations. The most common shape in Inca architecture was the rectangular building without any internal walls and roofed with wooden beams and thatch. There were several variations of this basic design, including gabled roofs, rooms with one or two of the long sides opened and rooms that shared a long wall. Rectangular buildings were used for quite different functions in almost all Inca buildings, from humble houses to palaces and temples. Even so, there are some examples of curved walls on Inca buildings, mostly in regions outside the central area of the empire. Two-story buildings were infrequent; when they were built the second floor was accessed from the outside via a stairway or high terrain rather than from the first floor. Wall apertures, including doors, niches and windows, usually had a trapezoidal shape; they could be fitted with double or triple jambs as a form of ornamentation. Other kinds of decoration were scarce; some walls were painted or adorned with metal plaques, in rare cases walls were sculpted with small animals or geometric patterns.

The most common composite form in Inca architecture was the kancha, a rectangular enclosure housing three or more rectangular buildings placed symmetrically around a central courtyard. Kancha units served widely different purposes as they formed the basis of simple dwellings as well as of temples and palaces; furthermore, several kancha could be grouped together to form blocks in Inca settlements. A testimony of the importance of these compounds in Inca architecture is that the central part of the Inca capital of Cusco consisted of large kancha, including the Temple of the Sun (Qorikancha) and the Inca palaces. The best preserved examples of kancha are found at Ollantaytambo, an Inca settlement located along the Urubamba River.

Inca architecture is widely known for its fine masonry, which features precisely cut and shaped stones closely fitted without mortar. However, despite this fame, most Inca buildings were actually made out of fieldstone and adobe as described above. In the 1940s, American archaeologist John H. Rowe classified Inca fine masonry in two types: coursed, which features rectangular shaped stones, and polygonal, which features blocks of irregular shape. Forty years later, Peruvian architect Santiago Agurto established four subtypes by dividing the categories identified by Rowe:

Encased coursed masonry: in which features stone blocks are not aligned
Sedimentary coursed masonry: in which stones are laid out in horizontal rows
Cellular polygonal masonry: with small blocks
Cyclopean polygonal masonry: with very large stones
The first two types were used on important buildings or perimeter walls while the last two were employed mostly on terrace walls and river canalization.

According to Graziano Gasparini and Luise Margolies, Inca stonemasonry was inspired by the architecture of Tiahuanaco, an archaeological site in modern Bolivia built several centuries before the Inca Empire. They argue that according to ethnohistorical accounts the Incas were impressed by these monuments and employed large numbers of stoneworkers from nearby regions in the construction of their own buildings. In addition to this references, they also identified some formal similarities between Tiahuanaco and Inca architecture including the use of cut and polished stone blocks, as well as of double jambs. A problem with this hypothesis is the question of how was expertise preserved in the three hundred years between the collapse of Tiahuanaco and the appearance of the Inca Empire and its architecture. As a solution, John Hyslop has argued that the Tiahuanaco stonemasonry tradition was preserved in the Lake Titicaca region in sites such as Tanka Tanka, which features walls resembling Inca polygonal masonry.

A second major influence on Inca architecture came from the Huari culture, a civilization contemporary to Tiahuanaco. According to Ann Kendall, the Huari introduced their tradition of building rectangular enclosures in the Cusco region, which formed a model for the development of the Inca kancha. There is evidence that such traditions were preserved in the Cusco region after the decline of the Huari as is attested by the enclosures found at sites such as Choquepuquio, 28 kilometers southeast of the Inca capital.