Frequently asked questions
When does a building need specific structural engineering design?
When it falls outside the scope of NZS 3604. That includes spans, heights, wall bracing demands or loadings beyond the standard tables, buildings on ground that is not good ground, importance level 3 and above structures, and any element such as a steel portal, a large opening, a cantilever or a transfer beam that the standard details do not cover. Council will generally expect calculations and a producer statement for the specifically designed elements.
Which structural standards apply in New Zealand?
Loadings come from the NZS 1170 series, including NZS 1170.5 for earthquake actions. Material design follows NZS 3101 for concrete, NZS 3404 for steel, NZS 3603 and NZS 3604 for timber, and NZS 4230 for masonry. These are cited as verification methods or acceptable solutions under Building Code clause B1, and compliance is normally demonstrated against them.
Do structural and geotechnical design need to be co-ordinated?
Yes, and the interface is where most requests for further information arise. The structural design sets the foundation loads and the tolerable settlement, and the geotechnical design sets the bearing capacity, the stiffness and the seismic site subsoil class. If those are developed independently the foundation design can be conservative, non-compliant, or both. Agreeing the site subsoil class and the settlement criteria early avoids rework at consent stage.