Our company is on the 12th floor of that office building.
Tips
usage
写字楼 literally means 'writing-character building' — a building where people do 'desk work'. This term originated in Cantonese-speaking areas and is now used nationwide.
usage
写字楼 specifically means an office/commercial building. 办公楼 (bàngōnglóu) is a synonym. Don't confuse with 住宅楼 (zhùzháilóu, residential building).