In BMC Flash, the building initially appears as an enclosed worker's building with corregated steel walls and a yellow roof. It has got a cylindrical chimney, windows on the roof, and a square open door with red beams. After unlocking one tier-4 upgrade, it appears to have a green roof, and the building itself gains an attic at the top, which has another window with similar red beams. (insert info for the one with all tier-4 upgrades unlocked)