Step 05
Realistic timeline and budget
A bump-out addition (kitchen bump-out, mudroom off the driveway side, or a small primary-bath extension against the tighter Vienna-rambler footprint (up to ~225 sq ft)) runs $110K–$175K and finishes in three to four months. A full room addition (full room addition — rear family room extension, primary suite bump-out with walk-in closet and spa bath, first-floor in-law suite, four-season sunroom, or a paired kitchen-and-family-room extension on the older Vienna Woods or Stonewall Manor ramblers (225–850 sq ft)) runs $175K–$375K and lands at four to six months on-site. A signature addition (second-story pop-top over a one-story rambler, full multi-generational wing with kitchenette and separate entry, attached ADU under Fairfax County's 800 sq ft / 40% cap, or a signature primary-suite wing matched to the teardown-Craftsman comps) runs $375K–$700K+ and takes six to ten months. Design plus permit adds five to nine weeks plus two to six weeks depending on which office (Town of Vienna or Fairfax County) plus two to four weeks at any HOA or historic-overlay review on the front end. Every proposal is fixed-price after the walkthrough.