Key Takeaways

• A second-story addition adds full floors of living space without changing your home's footprint, which suits the tight lots common across Chevy Chase, Bethesda, and Northwest DC.
• Your foundation, walls, and framing must be evaluated by a structural engineer before the design is finalized.
• Permits, zoning, and historic review shape what you can build, and timelines differ between Montgomery County and the District.
• Cost tracks with structural scope and finishes, so plan a 20 to 30 percent contingency and consult on cost during the design phase, not before.