B1/AS1: Structural provisions for buildings

B1 STRUCTURE ACCEPTABLE SOLUTION B1/AS1 General COMMENT: 1. Soils (excepting those described in (a), (b) and (c) above) tested with a dynamic cone penetrometer in accordance with NZS 4402 Test 6.5.2, shall be acceptable as good ground for building foundations if penetration resistance is no less than: a. 5 blows per 100 mm at depths down to twice the footing width. b. 3 blows per 100 mm at depths greater than twice the footing width. Depths shall be measured from the underside of the proposed footing. 2. The MBIE/MfE guidance document “Planning and engineering guidance for potentially liquefaction-prone land” outlines a risk-based process to identify and manage liquefaction-related risk in land use planning and development decision-making. 3. For houses built in areas that have the potential for liquefaction, the MBIE guidance document “Repairing and rebuilding houses affected by the Canterbury earthquakes” may be appropriate. This guidance provides a range of potential foundation solutions depending on expected ground movement and available bearing capacity. These parameters also determine the required degree of involvement of structural and geotechnical engineers and the extent of specific engineering design. 1.2.2 Modifications of standards 1.2.2.1 This acceptable solution contains modifications of cited standards in order to achieve compliance with the Building Code. The modifications are given for the relevant provisions in each standard. COMMENT: Raising the seismic hazard factor Z in NZS 1170.5 (Table 3.3) for the Canterbury earthquake region through amendments to B1/VM1 requires consequential amendments to NZS 3604, NZS 4229, and NZS 4299 referenced in B1/AS1. 1.2.3 Building Product Specifications 1.2.3.1 This acceptable solution refers to the Building Product Specifications for building product standards and specifications in relation to their manufacture, fabrication, testing, quality control, physical properties, performance, installation, and/or maintenance 1.2.3.2 The Building Product Specifications cannot be used in isolation to demonstrate compliance with any requirements of the Building Code. To comply with B1/AS1, building products conforming to the Building Product Specifications must be used with the scope, limitations, and other applicable requirements set out in this acceptable solution. MINISTRY OF BUSINESS, INNOVATION AND EMPLOYMENT 28 JULY 2025 Page 6