Start with what you have
Before drawing anything new, it helps to know what exists: the current foundation type, roofline, and whether you have existing plans for the home. If you don't have a copy of your original plans, that's common—we can often work from measurements and photos of the existing structure instead.
Questions worth answering before you request a quote
- What's the primary goal—more bedrooms, a bigger kitchen, a second story, an ADU?
- Roughly how much additional square footage are you adding?
- Does the addition need to tie into existing plumbing or electrical?
- Are you working with a contractor already, or still in the planning phase?
- Do you know if your project will need engineering (common for second stories or structural changes)?
What drives the cost of an addition
Like new construction, addition drafting is priced per square foot of the new space. Second-story additions and any project that alters the existing structural system (removing a load-bearing wall, adding a new floor above existing framing) typically move into the Architectural + Engineered tier, since a structural engineer needs to confirm the existing foundation and framing can support the change.
Setbacks and lot lines matter more for additions
Because an addition changes your home's footprint, your jurisdiction will usually want to see how the new structure relates to property lines and required setbacks—this is typically shown on an updated site plan. See Site Plans Explained.