What is the average cost to drywall a detached accessory dwelling unit in a Scarborough backyard?

A detached ADU in Scarborough typically requires $8,000-$18,000 for the complete drywall scope, including fire-rated assemblies, insulation coordination, hanging, taping, and paint-ready finishing. The wide range reflects unit size (400-1,200 square feet is common), finish level requirements, and the complexity of fire separation details required by the Ontario Building Code.

Detached ADUs present unique drywall challenges that drive costs above standard residential work. The Ontario Building Code requires a minimum 1-hour fire separation between the ADU and any other structure within 1.2 metres, which typically means 5/8-inch Type X fire-rated drywall on specific walls. The unit must also meet accessibility standards if it's the homeowner's primary residence, which can affect ceiling heights and door opening widths. Most Scarborough ADUs are built as complete separate dwellings with full kitchens and bathrooms, requiring moisture-resistant drywall (green or purple board) in wet areas and proper vapour barrier installation throughout.

Scarborough's housing patterns affect ADU drywall costs significantly. The area's typical 50-foot lot widths mean ADUs are often positioned close to property lines, triggering additional fire separation requirements. Many Scarborough properties have mature trees and established landscaping, making material delivery and waste removal more challenging than in newer subdivisions. The mix of older homes (many from the 1950s-1970s) means electrical and plumbing rough-ins may not align with modern drywall installation practices, requiring additional coordination and custom cutting.

Breaking down the drywall scope for a typical 600-square-foot Scarborough ADU: hanging drywall runs $3,000-$5,500 including fire-rated Type X where required, moisture-resistant boards in bathroom and kitchen, and standard 1/2-inch elsewhere. Taping and finishing to Level 4 (paint-ready) adds $2,500-$4,500, with Level 5 smooth finish in main living areas pushing this to $4,000-$7,000. Materials account for roughly 30% of total costs, with 5/8-inch Type X drywall running $20-$28 per sheet versus $14-$20 for standard 1/2-inch.

Timing and permit coordination significantly impact costs. ADU construction requires building permits and multiple inspections, meaning drywall installation must be precisely scheduled after electrical and plumbing rough-in inspections but before insulation and vapour barrier inspection. Winter construction in unheated ADUs requires temporary heating for proper joint compound curing, adding $200-$500 to the project. Many Scarborough ADU projects also include soundproofing considerations for neighbour relations, which can add $2,000-$5,000 for enhanced assemblies with resilient channel or QuietRock.

Professional installation is essential for ADU projects due to the fire rating requirements, permit inspections, and coordination with other trades. The fire-rated assemblies must be installed exactly to manufacturer specifications to maintain the 1-hour rating — a single incorrect screw placement can void the fire protection. Building inspectors specifically examine fire separation details, joint taping quality around fire-rated penetrations, and vapour barrier continuity.

Additional cost factors include waste disposal ($300-$800 for a typical ADU), which is higher in Scarborough due to narrow laneways and limited truck access in many areas. Premium finishes like coffered ceilings or custom bulkheads can add $2,000-$6,000. If the ADU includes a basement or lower level, expect 25-35% higher drywall costs due to moisture management requirements and more complex fire separation details.

Toronto Drywall Installers can help you find experienced contractors familiar with ADU requirements and Scarborough's specific site challenges. Most contractors will provide free estimates that break down the fire-rated assemblies, finish levels, and coordination requirements specific to your ADU design and lot conditions.