What a Home Addition Costs in the DMV
2026 planning guide · updated August 16, 2026
A home addition in the DC area runs $250–$450 per square foot in 2026 for typical single-story space — so a 400 sq ft family-room addition lands around $100,000–$180,000 built out. Bump-outs cost less per foot of impact, second-story additions more. Here are the honest ranges by type, and where the money actually goes.
Addition costs by type (DMV, 2026)
| Addition type | Typical planning range |
|---|---|
| Bump-out (2–4 ft, kitchen or bath relief) | $30,000 – $60,000 |
| Single-story addition, 300–500 sq ft | $85,000 – $200,000 |
| Primary-suite addition (bed + bath) | $120,000 – $240,000 |
| Second-story addition (over garage or wing) | $150,000 – $350,000 |
| Sunroom / three-season room | $40,000 – $90,000 |
Where addition money goes
- Foundation & shell (~35%): footings, framing, roof tie-in, siding match — the tie-in to the existing structure is skilled work that separates good bids from cheap ones.
- Systems (~20%): extending HVAC, electrical service capacity, and plumbing runs. An undersized panel or furnace can add $5,000–$15,000 nobody mentioned.
- Interior finish (~30%): the same per-foot money as any renovation — more if the addition is a kitchen or bath.
- Design, permits & engineering (~10–15%): DMV jurisdictions require sealed drawings for additions; budget $8,000–$25,000 before a shovel moves.
DMV notes worth knowing
- Setbacks decide feasibility: in Montgomery County, Arlington, and DC, the survey and zoning check come before any design money — many "additions" become bump-outs once setbacks are drawn.
- DC rowhouses: rear additions and pop-ups have their own zoning review; party-wall agreements add time, not just cost.
- Timeline: a typical DMV addition runs 3–5 months of construction after 2–4 months of design and permitting.
Get a range built from your kitchen, not a national average
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Plan your project with our estimator →Frequently asked questions
How much does a home addition cost per square foot in the DC area?
Plan on $250–$450 per square foot in 2026 for single-story additions with standard finishes, including design and permitting. Second-story additions and additions containing kitchens or baths price above that band.
Is a bump-out cheaper than a full addition?
Much cheaper in total dollars ($30,000–$60,000) because there's no new foundation footprint or roof structure in many designs — but the per-square-foot price is higher. Bump-outs shine when 30–60 sq ft fixes a cramped kitchen or bath.
Do I need an architect for an addition in Maryland or Virginia?
You need sealed drawings for permit in most DMV jurisdictions — from an architect or a design-build firm's engineer. Design-build (one contract for design and construction) is usually the faster path for residential additions.