Complex sentence: Most of the houses were built in the late-20th century, some homes are built with mud and brick as well as stone which was common until the mid- 20th century, a small fraction uses steel reinforced concrete.
Split into simpler sentences: Most of the houses were built in the late-20th century. Construction types include mud and brick, stone (which was common until the mid- 20th century), and a small fraction uses steel reinforced concrete.