RESILIENCE & DURABILITY
Designing for Resilience
Resilience is defined as the ability to return to the original form, position, etc., after being bent, compressed, or stretched. In a building sense, the bending, compressing and stretching would cause damage to the dwelling. Therefore, in a Healthy Homes sense, resilience is the ability to resist forces to some degree without damage.
To meet the performance requirements of New Zealand Building Code Clause B1 Structure, the Verification Method shall consist of AS/NZS 1170 used in conjunction with the relevant cited material.
Standards. https://www.building.govt.nz/building-code-compliance/b-stability/b1-structure/
AS/NZS 1170.0 states
SLS1-the structure and non-structural components do not require repair after the SLS1 earthquake, snow, or wind event.
Simply put there should be no damage requiring repair following an event that matches but not exceeds a Serviceability Limit State (SLS) event.
Serviceability is defined as the ability of a structure or structural element to perform adequately for normal use under all expected actions. Where serviceability applies to a house (an Importance Level 2 Structure) the annual probability of exceedance is once in 25 years.
Adherence to this directive is the basis for designing all resilient Healthy Homes and one of the cornerstones of this design guide.
It is important to choose a site with the best ground conditions possible as this makes a resilient design easier to achieve and less costly to build.
Designing for Resilience should also consider key infrastructure. See the Other Considerations in the section on Foundation Design.
Designing for Durability
Durability is defined as the ability to resist wear, decay, etc., well; lasting; enduring.
Therefore, in a Healthy-Homes sense, durability is the ability to resist the requirement for maintenance for a prescribed period.
The New Zealand Building Code Clause B2 Durability sets the minimum requirements for durability. Under this clause, building materials, components and construction methods are required to be sufficiently durable. They must ensure that the building, without reconstruction or major renovation, continues to satisfy the other functional requirements of the Building Code throughout its life. B2 specifies minimum durability periods building elements must meet with only normal maintenance, being not less than 50, 15 or 5 years.
For more information https://www.building.govt.nz/building-code-compliance/b-stability/b2-durability/
Kāinga Ora have recently stated that they are building-to-rent for not less than 70 years. The Superhome Movement applauds this initiative and believes that residential dwelling lifespans in New Zealand are inherently longer than 50 years and therefore the legislation should be amended to suit reality.
Recommended Healthy Home guidelines for Resilience and Durability design are set out in the table below:
