Granny Flats Design Choices That Often Lead to Council Objections
Granny flats (often called ancillary accommodation) look simple on paper: a compact dwelling, usually tucked behind an existing home, designed for family, guests or rental income. In practice, councils push back when a proposal feels like a “second house” squeezed onto a block without enough thought for access, amenity, privacy, parking and servicing.
If your goal is a smoother approvals process, the best time to avoid friction is the concept stage. Below are the design mistakes that most commonly trigger requests for changes, additional reports, or a straight refusal.
- The Trap of the 70 Square Metre Limit
In Western Australia, size is the most frequent point of contention. Most local councils strictly enforce a 70 square metre maximum for the internal floor area.
Some homeowners try to squeeze in “extra” space through large porches or carports. Councils see through this quickly.
If the structure feels too large, it is no longer “ancillary.” It becomes a second house in the eyes of the law.
This change in classification triggers much stricter rules. You might face higher headworks charges or even a flat refusal.
Using residential drafting services ensures your internal dimensions stay within the legal limits from the start.
- Ignoring Boundary Setback Requirements
Every suburb has specific “setbacks.” These define how far your building must sit from the fence.
Property owners often try to tuck the granny flat into a corner to save yard space. This often violates the Residential Design Codes (R-Codes).
If you build too close to a boundary, you block airflow and light. Councils prioritise the “amenity” of the neighbouring properties.
A building that sits too close to a fence often requires neighbour comments. If a neighbour objects, the council is likely to side with them.
The drafting Perth experts know how to read these site-specific constraints before you apply.
- Privacy and the “Cone of Vision”
Privacy is a major concern for Perth planners. They use a concept called the “cone of vision” to assess new builds.
If your granny flat has large windows overlooking a neighbour’s pool, it will be rejected. This also applies to raised decks or balconies.
You cannot simply build a high-set floor without considering who can see what. You may need to use obscured glass or high-sill windows.
Fixed screening is another common solution. However, these screens must meet specific height and transparency standards.
Failing to show these privacy measures on your initial plans is a common mistake. It suggests you have not considered the impact on the street.
- Aesthetic Mismatch with the Main House
Councils often demand that a granny flat matches the “character” of the existing home. This is particularly true in established or heritage-heavy suburbs.
Building a modern metal box behind a classic brick-and-tile home often causes friction. The materials and colours should ideally relate to the primary dwelling.
Roof pitches are another area where designs often fail. If the main house has a steep gable, a flat-roofed flat might look out of place.
An architectural design service Perth helps create a cohesive look. This visual harmony makes the council more likely to approve the plans.
- Parking and Access Complications
Adding a second dwelling usually means adding at least one car. Most councils require a dedicated parking bay for the granny flat occupant.
This bay must be accessible and separate from the main driveway if possible. You cannot always rely on street parking to meet your requirements.
Pedestrian access is equally vital. There must be a clear, safe path from the street to the new front door.
If the path is too narrow or obstructed, it becomes a safety issue. Councils look for “universal access” in many modern dwelling designs.
A dedicated drafting company Perth can map out these vehicle movements on your site plan.
- Neglecting Stormwater and Drainage
Perth’s sandy soil handles water well, but you still need a plan. You cannot allow rainwater from a new roof to flood a neighbour’s garden.
Councils require a detailed stormwater management plan. This usually involves installing soakwells of a specific size.
Many owners forget to account for the space these soakwells take up underground. They might clash with tree roots or existing sewer lines.
If your block has a slope, the drainage issues become even more complex. You might need retaining walls, which require their own set of approvals.
- Overlooking the Bushfire Attack Level (BAL)
Many parts of Perth are now classified as bushfire-prone areas. If your property is in one of these zones, you need a BAL assessment.
A high BAL rating changes the materials you can use. You might need toughened glass, specific spark guards, or non-combustible cladding.
Designing a flat without checking the BAL map is a recipe for a budget blowout. You might design a timber deck that is legally impossible to build.
Getting this assessment done early saves you from redesigning the entire structure later. It is a technical step that cannot be skipped.
- The Difficulty of Utility Connections
A granny flat needs power, water, and deep sewerage. Connecting these to the existing house lines is not always simple.
If your existing sewer pipe is too shallow, the new flat might need a pump. If the electrical mains are old, you might need a costly upgrade.
Planners want to see how these services will reach the new building. They also check if the new structure sits over an existing easement.
Building over an easement is generally prohibited. It can lead to the council ordering the demolition of the structure.
Those looking for commercial drafting services near me often find that even small residential sites have complex service needs.
- Navigating Local Planning Policies
Every Perth council has its own “local planning policies” (LPPs). These sit on top of the state-wide R-Codes.
One council might allow a 70sqm flat, while the next one limits it to 60sqm. Some have specific rules about where the front door faces.
Generic designs from the internet rarely meet these local nuances. They are often built for different climates or legal frameworks.
A custom approach is the only way to guarantee a smooth path through the city’s planning department. Engaging drafting services Perth provides the local knowledge needed for success.
Final Thoughts on Design Compliance
Success in building a granny flat depends on the quality of your documentation. A “near enough” approach leads to delays and extra fees. Clear plans show the council that you are a responsible developer. A well-designed ancillary dwelling adds significant value to your life and your property. It is worth the effort to get the design right the first time.
