Improve the logic in the paragraph
Exterior staircases leading up to second, third, or even fourth-storey apartments are common in many neighbourhoods, in part. Historically this reduced the size of buildings and therefore decreased the owner's property taxes.
Exterior staircases leading up to second, third, or even fourth-storey apartments are common in many neighbourhoods, in part because historically this reduced the size of buildings and therefore decreased the owner's property taxes.