Sometimes a prospective client will ask "what's the cost per square foot for building a home addition." Our standard answer is: We'll find out after we've built it--when we divide the finished square footage by the total tab. I'm not being a smart aleck. Honestly. How could we know the cost of something we haven't even designed yet?
This is a fundamental difference between custom home renovation and new home building. In renovation we are typically adding less than 1,000 square feet of new space--even when the program calls for a two story addition. Whereas, the square footage sweet spot for a new infill home is around 3600 square feet.
Custom renovation appears to be much more expensive (per square foot) than the new home. Why? because in a new build, the cost of the most expensive rooms in the house (kitchens and baths) gets spread over double or triple the square footage. Most Washington DC home additions must be built to fit on fairly small lots. Most home additions involve less than 1,000 square feet of new space. So there is no place to hide cost of the big ticket features. It's really about scale. Producing many square feet of product gives the appearance of low (per square foot) unit cost. Custom renovation, particularly additions (for master suite, modern kitchen and family room) pack a lot of quality into a small area adding tremendous value into the home. So, trying to put a value based on size (cost per square foot) is a deeply flawed basis for comparison.
Consider this. "Custom" costs more than "off the shelf." By way of example, here is a first floor layout for a two story addition we designed for a Washington DC home remodel residence.
This design plan was conceived to enhance the unique characteristics of the existing house and to free it of its former limitations. Everything about it is custom. Compare the size of the old kitchen (left) with the new design (right). Also, you can see that we expanded the dining room (right) when we eliminated the old kitchen. The old living room (left) was reconfigured to create a foyer and den (parlor).
There are many small changes and reconstructions to note, but it should be clear to you now that the process (and cost) of home additions and renovation is nothing like new home building. We pack a lot of thought, care and value into a comparatively small space.
To learn more about renovating a home, download the free eBook: "The Essential Elements of Renovating an Older Home."