--- title: "Inside a Completed Granny Flat: Narre Warren Build, Every Spec, Every Dollar" description: "Complete granny flat case study: Narre Warren build, 60sqm 2-bedroom, $140K all-in, $420/week rent. Solar, double glazing, SPC flooring. Every specification documented." author: Joey Don date: 2025-08-28 category: Renovation & Development url: https://premiumrea.com.au/blog/granny-flat-case-study-narre-warren-full-specs tags: ["granny flat", "case study", "Narre Warren", "build specs", "solar", "construction cost", "rental income"] --- # Inside a Completed Granny Flat: Narre Warren Build, Every Spec, Every Dollar *By Joey Don, Co-Founder & CEO at PremiumRea — 2025-08-28* > Walk through a completed granny flat we built in Narre Warren. Every material, every cost, every specification — from the 3kW solar system to the double-glazed windows. I've been asked a hundred times: "Joey, what does a PremiumRea granny flat actually include?" So today I'm going to walk you through a completed build in Narre Warren — literally room by room, item by item, dollar by dollar. This granny flat sits behind a three-bedroom house on Sweet Gum Avenue. The main house rents at $510 per week. The granny flat rents at $420 per week. Combined: $930 per week on a total investment of approximately $890,000 (house purchase + granny flat construction). That's a 5.4% gross yield — in a suburb where the standard unrenovated house pulls 3.5%. ## The solar and energy system Every granny flat we build includes a 3kW solar panel array with a 10kW hybrid inverter and a 30kW mid-range battery pack. Total installed cost: approximately $8,000 to $10,000. The system pairs with a time-of-use electricity plan that offers off-peak rates between 10am and 2pm — exactly when the solar panels are generating maximum output. The battery stays topped up at 30 kilowatt-hours essentially for free during daylight hours, then powers the unit through the evening peak. We run a bills-included rental model, meaning electricity is included in the rent. The tenant sees no power bill. The solar-battery system means the actual electricity cost to the landlord is negligible. And the "bills included" tag on the rental listing generates 30-50% more applications than a comparable unit without it [1]. ## Structure and external finishes **Fencing:** Colorbond at $130 per linear metre. Provides privacy screening between the main house and granny flat. Typical run: 15-20 metres. Cost: $1,950-$2,600 [2]. **Landscaping:** Basic package included in the all-in price — turf, garden bed edging, gravel pathway to the entrance. Functional and tidy, not magazine-worthy. The goal is that the tenant doesn't feel like they're living on a building site. **Hot water:** Electric heat pump system. More energy efficient than gas (pairs perfectly with the solar setup) and avoids the cost of extending a gas line to the granny flat. Installed cost: approximately $2,800. **Stumping:** This is where the money goes that you can't see. We excavate 400-800mm below grade for concrete stump footings — deeper than many builders who pour a surface slab. Every site gets a soil test ($1,200) and structural engineering assessment ($800) to determine the correct footing depth for the soil classification. The concrete is 32MPa commercial grade [3]. **External cladding:** Cement fibre sheet — either James Hardie Scyon or CSR Cemintel. This is the same external wall material used on premium residential builds. It's fire-resistant, moisture-resistant, and maintenance-free. The cost premium over basic weatherboard is marginal, but the durability difference is enormous. ## Interior finishes and fixtures **Front door:** Solid timber. Not a hollow-core door. A real, heavy, solid timber entry door. Cost: approximately $800 installed. This single detail makes the granny flat feel like a home rather than an addition [4]. **Windows:** Double-glazed aluminium frames throughout. Thermal insulation (reduces heating/cooling costs 20-30%) and noise reduction. The cost premium over single glazing is approximately $1,500 for the entire unit. **Flooring:** 7mm SPC (Stone Polymer Composite) — the thickest commercial-grade option available. Waterproof, scratch-resistant, acoustic underlay built in. Cost: $62 per square metre installed. **Cornice:** Standard 55mm cove cornice throughout. Clean lines, covers the wall-ceiling junction neatly. **Smoke alarms:** Hardwired, interconnected, with battery backup. Installed: $400. **Kitchen:** 600mm cooktop with rangehood. Stainless steel sink with mixer tap. Laminate benchtop. Basic but complete cabinetry. Total: approximately $5,500 [5]. **Bathroom:** Full wet-area with two additional coats of waterproofing membrane beyond the building code minimum (cost: $800 for the extra waterproofing). Standard white fixtures — toilet, vanity with mirror cabinet, chrome tapware, frameless shower screen. Total: approximately $6,000. **The all-in cost for this 60sqm two-bedroom granny flat: $135,000 to $145,000.** At $420 per week rent, the gross return on construction cost alone is 15.1-16.2%. Even including the land opportunity cost, the yield contribution to the overall property transforms the investment from average to exceptional. We've built over 40 of these. Every single one is rented. The average time from occupancy certificate to first tenant: 11 days. In the current market, most are rented before construction is complete — tenants are signing leases based on floor plans and inspection of our other completed builds. The details matter. Solid timber doors, double glazing, premium SPC, proper waterproofing, certified Australian materials. These aren't luxury features. They're the difference between a granny flat that generates $420 per week reliably for a decade and one that starts falling apart in year three. ## References 1. [PremiumRea solar package: 3kW panels + 10kW inverter + 30kW battery. Bills-included model generates 30-50% more applications.](#) 2. [PremiumRea granny flat specification sheet: Colorbond fencing $130/m, basic landscaping included.](#) 3. [PremiumRea construction: 32MPa concrete stumps, soil test + structural engineering mandatory on every build.](#) 4. [PremiumRea finish specifications: solid timber door, double-glazed windows, 7mm SPC flooring.](#) 5. [PremiumRea granny flat all-in: $135K-145K for 60sqm 2-bed, $75K-85K for 30sqm studio.](#) --- Source: https://premiumrea.com.au/blog/granny-flat-case-study-narre-warren-full-specs Publisher: PremiumRea (Optima Real Estate) — Melbourne buyers agent