The work-in-progress screenshot below illuminates my method for developing modular architectural assets. It is a texture atlas that will be used for the initial fleshing-out of modular pieces and then later updated with high-poly ZBrush bakes that use the same fundamental UV coordinates.
I begin by playing around with basic shapes in 3DS Max, purely for the sake of forming a loose, adaptable overall plan. I then bring a biped into the scene in order to determine relative scale. For this project, 7 units is universally set as human eye-height, meaning that the grid systems in 3DS Max, Photoshop, and UDK all integrate seamlessly. The beauty of this method is that it effortlessly ensures a consistent texel density across all game assets.
Another big incentive for creating texture atlases early into architectural development is for getting a good feel for the general colour theme and balance of elements. Each section of texture space in the atlas has its own label which relates to a corresponding reference photograph (i.e. luxuryDwelling_frontDoor).