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  Universal Design Costing Estimator


It is considerably cheaper to build universal design (UD) features into a new house compared to retrofitting the same house. This is true for any house type and size. In 2011, BRANZ conducted research to determine the likely costs of UD for a range of variables, such as house size, new-build versus retrofit and the extent of changes needed to bring the design up to a minimum level of performance.

The core features selected to make a home meet a minimum UD level are based on accessibility, usability and inclusiveness. Two standards were used to determine what these minimum features needed to be: NZS 4121: 2001 Design for access and mobility: Buildings and associated facilities and the LifeMark specification.

The resulting core UD features selected are as follows:

  • All internal passageways at least 1.05 m wide.
  • The largest bedroom on the primary living level is at least 4.4 m x 3.15 m or 3.8 m x 3.75 m.
  • The kitchen is at least 2.7 m x 2.1 m to provide the required turning circle and distance between benches for a wheelchair.
  • The space for the bathroom and toilet is 2.95 m x 2.1 m. If the bathroom and toilet are separate but next to each other, the combined size is used.
  • All internal and external doors have an 810 mm clear opening.
  • Strengthening of walls via extra dwangs in the bathroom and toilet.
  • All power sockets and light switches are between 0.9 m and 1.2 m above floor level.

Average costs (inclusive of both materials and labour) for these adaptations were built up from a sample of 83 new and 112 existing house designs from previous BRANZ research.

Key findings

  • For a house of between 150 and 200m2, the cost of incorporating essential UD features costs about $1700 for a new house compared to $14,000 if that same house was to be retrofitted.
  • In most situations, the extra cost of incorporating UD features into any new house will usually be less than 0.5% of its total build cost.
  • For internal changes only, about 80% of new houses require either no or minor changes to layout, doors and strengthening of bathroom fittings prior to construction. These adaptations add around only $500 or less to the total new house cost.
  • In terms of external changes, many new houses require wider parking areas and better access to the front door. These changes typically add another $1,200 to the house cost.
  • When changes are made to existing houses, the costs are typically $15,000 per house for internal work and another $7,000 for ramps and other external access features.

For more information on the background to costings, refer to the freely downloadable BRANZ Study Report 263 Lifetime housing - the value case.

Costing estimator tool

This tool estimates the costs of incorporating key universal design features for your particular situation. Note that these costs, although based on many actual homes, are indicative. Both material and labour costs are included in the costings.

Steps to determining your specific costs:

  1. Select how many of the core features your house meets (from the key findings above)
  2. Using the drop-down menus below, select whether your house is a 'New Build' (i.e. is still at the design stage) or a 'Renovation'.
  3. Select the extent of the key changes necessary, where:
    'Major' = the shifting of at least one room
    'Minor' = the shifting of some walls, with no rooms shifted.
    'Minimal' = the strengthening of walls in the bathroom/toilet areas, only.
  4. Select what areas to include in the change and the floor area of the house.

A total costings figure (based on 2011 prices) for adapting your house will be automatically provided.

Will you upgrade the interior or exterior?
Type of Build
Extent of Changes
Floor Area of House
New Exterior Ramp
New Entry Porch
Interior Average Qty Cost per Qty Cost
Moving Walls $ $
Increase House Size $ $
External Doors $ $
Internal Doors $ $
Toilet/Bathroom Wall Strengthening $
Moving Power/Light Switches $
Exterior Type Cost
New Exterior Ramp $
New Porch $
Total Cost $