B1/AS1: Structural provisions for buildings

B1 STRUCTURE ACCEPTABLE SOLUTION B1/AS1 General Part 1. General 1.1 Introduction 1.1.1 Scope of this document 1.1.1.1 This acceptable solution can be used to determine the structural provisions for buildings along with other specific building elements including: a) masonry buildings; and b) steel buildings; and c) timber buildings; and d) earth buildings; and e) stucco; and f) drains; and g) glazing. 1.1.1.2 Limitations on the scope of this acceptable solution are specified in each of the cited standards along with the modifications and additional requirements stated in this document. 1.1.2 Items outside the scope of this document 1.1.2.1 This acceptable solution does not contain provisions for small chimneys. For small chimneys, refer to Acceptable Solution B1/AS3 or use an alternative means to demonstrate compliance. 1.1.2.2 Foundations for houses where good ground has not been established and the ground has the potential for liquefaction or lateral spread are outside the scope of the acceptable solution. Refer to Subsection 1.2.1 for how good ground is established. 1.1.3 Compliance pathway 1.1.3.1 This acceptable solution is one option that provides a means of establishing compliance with the functional requirements and performance criteria in Building Code clause B1 Structure. It can be used to demonstrate compliance with clauses B1.2, B1.3.1, B1.3.2, B1.3.3, B1.3.4, B1.3.5, B1.3.6, and B1.3.7. 1.1.3.2 If this acceptable solution cannot be followed in full, use an alternative means to demonstrate compliance. 1.2 Using this acceptable solution 1.2.1 Determining when good ground has been established 1.2.1.1 Good ground includes any soil or rock capable of permanently withstanding an ultimate bearing pressure of 300 kPa (i.e. an allowable bearing pressure of 100 kPa using a factor of safety of 3.0), but excludes: a) potentially compressible ground such as topsoil, soft soils such as clay which can be moulded easily in the fingers, and uncompacted loose gravel which contains obvious voids; and b) expansive soils being those that have a liquid limit of more than 50% when tested in accordance with NZS 4402 Test 2.2, and a linear shrinkage of more than 15% when tested, from the liquid limit, in accordance with NZS 4402 Test 2.6; and c) any ground which could foreseeably experience movement of 25 mm or greater for any reason including one or a combination of: land instability, ground creep, subsidence, liquefaction, lateral spread, seasonal swelling and shrinking, frost heave, changing ground water level, erosion, dissolution of soil in water, and effects of tree roots. MINISTRY OF BUSINESS, INNOVATION AND EMPLOYMENT 28 JULY 2025 Page 5