Home / Granny flat designs / One 40
One 40: 1 bedroom, 40 m²
A long, simple 10 × 4 m plan: bedroom at one end, living at the other, kitchen and bathroom in the middle.
Who it suits
The most popular one-bedroom rental size. Also suits a parent who wants room for visitors.
Features
- Tri-track sliding glass door to the living area
Specification
| Floor area | 40 m² |
| Overall size | 10 m × 4 m |
| Bedrooms | 1 |
| Bathrooms | 1 |
| Cladding | Timber-look composite (WPC) cladding |
| Floors | Engineered flooring in living and bedroom, 600 × 600 ceramic tiles in wet areas |
| Frame | Light-gauge steel, G550 grade with AZ150 coating to AS 1397. Termite-proof and won't warp or rot. |
| Roof | 0.5 mm Colorbond sheet roof on steel battens, with aluminium gutters and downpipes |
| Insulation | R2.5 glass wool in external walls and internal walls, plus ceiling insulation |
| Windows | Aluminium windows, double-glazed |
| Kitchen | Cabinets, benchtop, sink and mixer |
| Bathroom | 900 × 900 shower, vanity and WaterMark-certified toilet |
| Electrical | Wiring, switchboard and connections completed and certified by a licensed WA electrician |
Specification is the standard baseline and is confirmed in your quote.
How it gets to your backyard
The One 40 is made in a factory as a folding steel-frame module. While it is being made we lodge the building permit and prepare your slab and service connections. It then arrives on a truck, is craned onto the slab and unfolded in about one to two days, and our licensed trades connect and finish it. See the full timeline.
Similar designs
Two 40
- 40 m²
- 2 bed
- 2 bath
- 10 × 4 m
Fixed price after a free site visit
One 37
- 36.6 m²
- 1 bed
- 1 bath
Fixed price after a free site visit
Common questions
How much does the One 40 cost?
We give you a fixed price after a free site visit, because site works, access and connections vary a lot between blocks. See our Perth granny flat cost guide for typical market ranges.
Do I need council approval for the One 40?
You always need a building permit, which we lodge for you. You only need development approval as well if the flat does not meet the deemed-to-comply rules for your lot or your lot has special planning controls.
See what fits in your backyard
Book a free site visit. A registered builder checks your block, access and services, then sends a fixed-price quote.