墙壁 (qiángbì) is a noun meaning "wall." It refers to the vertical structural surface of a building or room. Unlike 墙 (qiáng) alone, 墙壁 often emphasizes the surface itself, such as when describing its condition or appearance.
这面墙壁上挂满了家人的照片。
Zhè miàn qiángbì shàng guà mǎn le jiārén de zhàopiàn.
This wall is covered with family photos.
师傅说墙壁需要重新刷一遍漆。
Shīfu shuō qiángbì xūyào chóngxīn shuā yī biàn qī.
The worker said the walls need to be repainted.
墙壁上出现了一条很长的裂缝。
Qiángbì shàng chūxiàn le yī tiáo hěn cháng de lièfèng.
A long crack appeared on the wall.