Can an old granny flat be brought up to code for legal renting?

Often yes, but it depends on the existing structure. A builder or building surveyor needs to inspect it first to identify what doesn't meet current requirements.

Is renovating an existing granny flat cheaper than building new?

Usually cheaper if the structure is sound, since you're not paying for a new slab, frame and roof, but hidden compliance issues can close that gap.

Do I need approval to renovate an existing ancillary dwelling?

Depending on the scope, yes, particularly if you're changing the kitchen, bathroom, or floor area. Check with your local council before starting.

Renovating or upgrading an existing granny flat

Plenty of Perth properties already have an older granny flat, converted garage, or ancillary dwelling that needs updating rather than a brand new build from scratch. This might mean re-lining walls, replacing an old kitchenette, upgrading the bathroom, or bringing an unpermitted structure up to current standards so it can be legally rented out or used as a second dwelling.

This is a different job from building a new granny flat: it involves working within an existing footprint and structure, often uncovering issues like non-compliant wiring, plumbing or insulation that need fixing before the flat can be signed off for use. Buyers searching for this usually already own the structure and want it made livable, compliant, or more rentable.

Builders who take this on need to assess the existing structure's condition first, which usually means a site visit before any fixed quote, since the scope depends heavily on what's hiding behind the walls.

What it costs

Cost depends heavily on the condition of the existing structure and whether compliance issues (wiring, plumbing, insulation, permits) surface once work starts. A full kitchenette and bathroom upgrade inside an existing flat costs less than a new build of the same size, but unexpected structural or compliance fixes can add to the quote after the first inspection.

Top 3 by our score

Ranked from our published scoring of public Google reviews for granny flats & adus.

1. HomeLux Renovations
5.0★ · 50 reviews

88
2. Modus Property
4.9★ · 193 reviews

88
3. Hatch Renovations
4.8★ · 38 reviews

85

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FAQ

Can an old granny flat be brought up to code for legal renting?: Often yes, but it depends on the existing structure. A builder or building surveyor needs to inspect it first to identify what doesn't meet current requirements.
Is renovating an existing granny flat cheaper than building new?: Usually cheaper if the structure is sound, since you're not paying for a new slab, frame and roof, but hidden compliance issues can close that gap.
Do I need approval to renovate an existing ancillary dwelling?: Depending on the scope, yes, particularly if you're changing the kitchen, bathroom, or floor area. Check with your local council before starting.

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