Building Envelope: How three townhouses can become two

So you’ve heard about the “300 m2 per lot” rule of thumb used by planners for potential developments.

You factored this in as you purchased your 900 m2 block of land.

You’re sure to get a Planning Permit for three townhouses, right?

 

Building Envelope

On a pure square metre basis, a site may satisfy (and even exceed) the “300 m2 per lot” rule of thumb yet not be suitable for a Planning Permit.

Sometimes, the issue is purely physical – given all planning and legal constraints, the site simply cannot physically fit the number of units/townhouses desired.

This is because the Building Envelope is too small.

The Building Envelope is the area of land, within the title boundaries of a subject site that the proposed building/s can legally and physically occupy.

It does not appear on title nor on any official planning documentation – rather it is the result of the specific planning constraints that apply to the site given the development you propose.

Building Envelope Example

Consider the picture above.

Even though this hypothetical block may well be above 900 m2, there are four constraints marked on the site:

  1. There is an “E-1 Easement” running parallel to the rear fence.
  2. There is a significant “Average Front Setback” for this street which cannot be built in front of
  3. There is an allowance for the Driveway
  4. There is an allowance for “Private Open Space”

These four constraints alone can effectively halve the Building Envelope.

Victoria’s Planning Scheme for residential developments (Clause 55) defines 34 such constraints.

Consequences

When a Building Envelope is too small, compromises sometimes need to be made that can significantly impact the proposed subdivision/development.

The typical compromise is that building area is saved by reducing car parking which therefore affects bedrooms.

So for example, a triple three bedroom townhouse development all with double garages may need to be scaled back to two three bedroom townhouses with double garages and a two bedroom unit with single garage.

The worst case scenario is that a proposed three townhouse development may need to be scaled back to two.

Needless to say, compromises with dwelling type and configuration affect the profitability – and in some cases the feasibility – of the proposed development.

Conclusion

The Building Envelope is the area of land, within the title boundaries of a subject site, that the proposed building/s can legally and physically occupy.

It does not appear on title nor on any official planning documentation – rather it is the result of the specific planning constraints that apply to the site given the development you propose.

If a Building Envelope is too small, compromises need to be made that can significantly impact the proposed subdivision/development and its feasibility.

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Building Envelope: How three townhouses can become two