noun which may take the genitive case particle 'no', noun
half-built; partially constructed
Describes a building or structure that is still under construction, not yet finished. Often used with の to modify a noun.
半建ての家が並ぶ新興住宅地。
A new residential area lined with half-built houses.
台風で半建てのビルが倒壊した。
The half-constructed building collapsed in the typhoon.
建設中 means 'under construction' and is more common and general. 半建て specifically emphasizes the incomplete, half-finished state of a building.
Compound of 半 (half) and 建て (building, from 建てる 'to build'). The exact historical derivation is uncertain, but the word transparently means 'half-built'.