Basement Second Unit Cost in Oakville

Measure rough ceiling height at multiple points (concrete floor to underside of joists). Check for water stains, efflorescence, or musty odors indicating moisture problems. Verify electrical panel capacity (load calculation — if your main panel is 100A and heavily loaded, you need a service upgrade to 200A). Confirm zoning allows second units (Bill 23 overrides most restrictions, but check local bylaws). Identify potential egress locations for bedrooms.

Hire a designer or architect to produce drawings showing: floor plan with room dimensions and ceiling heights, egress window sizes and locations, fire separation details (floor/ceiling assembly, demising walls, door ratings), electrical panel location and circuits, plumbing fixture locations and drain routing, HVAC system and fresh air intake. Drawings must demonstrate OBC compliance — inspectors will check these line-by-line. Include detail drawings of the fire-rated assembly (gypsum layers, resilient channels, insulation).

Submit drawings to municipal building department with permit application fee ($800-$2,000 depending on project value). Toronto takes 6-8 weeks for review; smaller municipalities may be faster. Expect requests for revisions — common issues are egress window sizing, fire separation details, or plumbing drain capacity calculations. Some municipalities require a site plan showing parking (e.g., Toronto wants 1 space per unit, but Bill 23 prohibits requiring additional parking for second units within 800m of transit).

If ceiling height is below 7'2" rough, underpin the foundation before framing. Excavate 4-5 feet below existing footing in 3-4 foot sections (pins), pour new concrete footings and walls, repeat around perimeter. This lowers the basement floor by 12-18 inches and provides code-compliant ceiling height. See the Underpinning service page for full process — this adds $50,000-$75,000 and 4-6 weeks to the project.

Frame demising walls between units with 2x4 studs at 16" O.C. Install fire-rated door frames with ULC-listed self-closing hinges. Run new electrical sub-panel (60-100A) with dedicated circuits for kitchen, bathroom, laundry, heating. Rough-in plumbing — drain lines must slope 1/4" per foot, vent stack must extend through roof or tie into existing vent. Install HVAC — either extend existing forced air with dampered zones, or add separate system (mini-split is common). Inspections: framing inspection (fire separation verification), rough electrical (ESA), rough plumbing, rough HVAC/gas (TSSA if gas appliances).

Install mineral wool batts in demising walls and floor/ceiling assembly (R-12 minimum for sound control, higher for thermal separation if basement is conditioned separately). Install 5/8" Type X gypsum board on demising walls and ceiling per fire-rated assembly specification — this usually means two layers on the unit separation wall. Use fire-rated sealant (red acoustical caulk) at all penetrations — electrical boxes, pipe chases, duct boots. Install fire-rated doors: 20-minute rating for bedroom doors (solid core with ULC label), 45-minute rating for unit separation door. Mount self-closing devices — spring hinges or overhead closers. Inspection: insulation and fire separation (critical — inspector will check gypsum type, screw spacing, sealant application).

Finish drywall (mud, tape, sand), prime and paint. Install flooring — LVP or laminate over subfloor and underlayment. Install kitchen cabinets and countertops. Install bathroom vanity, toilet, shower/tub. Install interior doors and trim. Connect electrical devices (outlets, switches, light fixtures). Connect plumbing fixtures. Install appliances (stove, fridge, washer/dryer if in-unit laundry).

Book final inspections: building final (fire separation, egress, ceiling height verification), ESA final (electrical panel, circuits, devices), plumbing final, HVAC/gas final. Install interconnected smoke alarms and carbon monoxide alarms per OBC 9.10.18 — one in each bedroom, one outside sleeping areas, one per storey, all interconnected (wireless or hardwired). Inspector will test alarm interconnection. Once all inspections pass, receive occupancy permit. Register with municipal rental licensing if required (Toronto: RentSafeTO registration within 30 days).