Red Dragon Terrain are now offering Modular Urban Ruins.
From their announcement:
This is the first completed piece I have in a series of 28mm urban buildings, designed to be modular in nature.
Each floor is a stacking level, and the top can be substituted with a battle damaged version to indicate, well, battle damage.
Interior floors have a wood planking finish and the roof is a “tar and gravel” texture.
This model is made from unfinished plastic, and ships in large pieces, so building it is easy.