Home Extension Builders in Johannesburg

Single-storey extensions cost R10,000–R16,000 per square metre in Johannesburg in 2026. A 30 m² room addition costs roughly R300,000–R480,000. Second-storey additions cost R15,000–R25,000/m² — 20–30% more due to structural reinforcement and working at height. A 40 m² granny flat costs R350,000–R750,000. These prices include construction only; architect plans and council submissions add R15,000–R40,000.

Yes. Every building extension in Johannesburg requires City of Johannesburg approved building plans. Without approved plans, the structure is illegal — it cannot be insured, cannot be bonded, and the municipality can order it demolished. Plans must be drawn by a SACAP-registered architect and approved by your local council (4–12 weeks). We handle the entire process for you.

Yes. A properly approved granny flat in Johannesburg generates R7,000–R14,000 per month in rental income, delivering an 18–25% annual return on the R350,000–R750,000 build cost. It also increases your property value. However, the unit must have council-approved plans and comply with zoning regulations. Unapproved structures have no legal rental protection and can be ordered demolished.

Not always. The existing foundations and walls must be strong enough to carry the additional load. We engage a structural engineer to assess your home before committing to a second-storey design. Some homes need foundation underpinning or wall reinforcement before going up. Older homes with shallow strip foundations may not be suitable without significant structural work. We give you an honest assessment during the free consultation.

A single-storey room addition (20–40 m²) takes 6–10 weeks. A second-storey addition takes 10–16 weeks. A granny flat takes 8–14 weeks. These timelines exclude the plans approval period (4–12 weeks). Weather, material availability, and municipal inspections can affect the schedule. We provide a detailed project timeline with your quote.