When adding square footage, the options are going out or going up. Determining factors include things like available lot space, how the new space will interact with the flow of existing rooms, and how to best interlink the new construction structurally. There is not a given square-foot price. Instead, each house is unique based on location considerations, chosen materials, and finishes.
The add-on is often built after other home interior remodels, and we make it all have the same feel, flow, and design. The exterior style and materials of the remodel match the rest of the home. The new construction will look like it has always been a part of the house. It will look great!