NYC brownstone renovations often take 6–12 months  from planning to completion. Many projects trigger Alt‑1  permits due to structural changes. Landmark review, DOB approvals, and tight site logistics set the pace. Why this matters in January January planning helps owners in Harlem, Park Slope, and Brooklyn Heights secure approvals before spring permit backlogs build. What makes brownstones different Brownstones are narrow, vertical, and often prewar. Common constraints inclu