Had serious plans to convert our attic into a master bedroom suite. Hired an architect and structural engineer for the feasibility study. Sharing what they found - it was a reality check that saved us from a $200K mistake.
The House
1952 Toronto 2-storey detached, 25 ft wide, gable roof. Attic peak height: 2.8m (9’2") at centre. Looked promising on paper.
What the Engineer Found
Ceiling joists: 2x6 at 16-inch spacing. Adequate as ceiling ties but would need to be completely replaced with 2x10 or 2x12 LVL to carry floor loads. With the existing joists, there is no room to sister - they would need full replacement, meaning the ceiling below would need to come down.
Minimum floor area at 2.1m: Only 55% of the floor could meet the 2.1m minimum height requirement (the code requires 50%, so this was barely feasible).
Stair access: Creating a code stair would require a 4x10 ft opening in the second floor, directly above a load-bearing wall. New header beam and post-down required.
Knob and tube: Opening the attic would require complete attic wiring removal.
The Real Scope and Cost
Structural engineer’s summary:
- Replace ceiling joists with engineered lumber: $18,000-$24,000
- Stair opening with header + post: $8,000-$12,000
- Dormer addition to increase headroom (recommended): $45,000-$65,000
- Insulation, drywall, electrical, window, egress: $35,000-$50,000
- Permits and engineering: $12,000-$18,000
Total estimate: $118,000-$169,000 for ~380 sq ft of finished space.
What We Did Instead
Decided to finish the basement instead (already adequate ceiling height, no structural work needed) for $85,000 and got 600+ sq ft.
Lesson: Get a Feasibility Study First
$2,200 for the engineering assessment saved us from assuming a $120,000-$170,000 project was a $60,000 one.