Find out attic and loft conversion costs to bedroom or office in 2026. Types and permit requirements compared. Free guide.
Converting an attic to livable space costs $20,000-$75,000 depending on scope — one of the lowest cost-per-square-foot ways to add space since the basic structure already exists. A simple attic bedroom costs $20,000-$35,000 while a full dormer addition with bathroom runs $40,000-$75,000. The payback is strong: attic conversions return 60-80% of cost at resale.
Cost ranges by scope: Basic attic finishing (if structurally suitable): $20,000-$35,000 — insulation, drywall, flooring, staircase. Attic bedroom with dormer addition: $35,000-$60,000 — adds natural light and headroom. Full dormer with ensuite bathroom: $50,000-$80,000. Mansard roof conversion (entire roof restructure): $75,000-$150,000. Key prerequisites: floor joists must support additional load — structural engineer evaluation recommended ($300-$700) before any planning.
Pre-conversion assessment: Headroom: minimum 7.5 feet at center for habitable space in most building codes. Floor structure: most attics not built for living load — may need sistering of joists ($2,000-$5,000). Staircase: code-compliant stairs required, minimum width 36 inches. Egress window: required in sleeping rooms, minimum 5.7 sq ft opening. Insulation: existing may need complete replacement ($2,000-$5,000). HVAC extension: $2,000-$6,000 to reach attic level.
Attic conversion ROI: Adds 10-20% to home value typically. On $400,000 home: $40,000-$80,000 added value. Cost: $30,000-$75,000. ROI: 60-80% typical. Better ROI than: sunroom or deck additions. Similar ROI to: basement conversions. Best ROI when: home is undervalued relative to neighbors due to fewer bedrooms, adding bedroom in high-demand school district, or converting to in-law suite with rental potential.
Attic bedroom conversion requirements: Habitable space code requires: minimum 70 square feet, 7.5 foot ceiling height over at least 50% of floor area, at least one window, egress window for emergency exit. Bedroom specific: egress window minimum 5.7 sq ft opening, 24 inch minimum height, 20 inch minimum width, within 44 inches of floor. Heating and cooling: required for habitable bedroom — cannot rely on opening windows.
Attic conversion timeline: Permitting: 4-8 weeks approval. Basic finishing (no dormers): 4-8 weeks construction. Dormer addition: 8-14 weeks. Full mansard conversion: 3-6 months. Can you live in home: yes — most work is internal attic, minimal disruption to main floors. Dormer construction: roof is opened for 1-2 weeks — weather protection required and typically provided by contractor.
Yes — every FreeFixo tool, including the How Much Does a Loft or Attic Conversion Cost in 2026?, is 100% free with no paywall, no premium tier, and no usage limits. You do not need to create an account, enter a credit card, or share an email.
The How Much Does a Loft or Attic Conversion Cost in 2026? uses the same formulas, rates, and reference data that financial planners, professionals, and government sources publish. Results are estimates intended for planning and education — for situations involving large sums or legal consequences, confirm with a qualified professional before acting.
No signup is ever required. The How Much Does a Loft or Attic Conversion Cost in 2026? runs entirely in your browser — your inputs are never sent to a server, and we do not store, track, or share your data. Open it, get your answer, close the tab.