B1/AS1: Structural provisions for buildings

B1 STRUCTURE ACCEPTABLE SOLUTION B1/AS1 Buildings and structures b) add the new clauses, tables, and figures: i) “7.5.13 Slab-on-ground in expansive soils 7.5.13.1 Identification of expansive soils 7.5.13.1.1 Should reasonable enquiry as outlined in 3.1.3 show any signs of expansive soils, the expansive soil class, as defined in AS 2870, shall be established by one or all of: (a) enquiry to the local territorial authority, and/or (b) reference to the certificate of suitability issued in terms of NZS 4431, and/or (c) a soil test undertaken by a suitably qualified soils engineer. 7.5.13.1.2 Expansive soil class shall be defined as: (a) Slightly ‘S’, having an I range of 0–1.9%, and a 500 year design characteristic ss surface movement return (ys) of 22 mm, or (b) Moderately ‘M’, having an I range of 2.0–3.7% and a 500 year design ss characteristic surface movement return (y ) of 44 mm, or s (c) Highly ‘H’, having an I range of 3.8–6.5% and a 500 year design characteristic ss surface movement return (y ) of 78 mm, or s (d) Extremely ‘E’, having an I range of 6.6–7.5% and a 500 year design characteristic ss surface movement return (y ) of 90 mm. s 7.5.13.2 Maximum aspect ratio of concrete slabs The aspect ratio of the concrete slabs or bays of concrete slabs, such as in the case of L, T or boomerang concrete slab shapes, shall not exceed 5 to 1 (length to width). 7.5.13.3 Foundation details 7.5.13.3.1 For the identified expansive soil class the foundation details, external and internal thickenings shall be as follows. (a) For light wall claddings refer to Table 7.4A and Figure 7.22. (b) For medium wall or heavy wall claddings refer to Table 7.4B and Figure 7.23. 7.5.13.3.2 Situations where no internal thickenings shall be required are limited to a rectangular slab with long side not exceeding 17.0 m. Where this limit is exceeded, add additional internal thickenings across the slab with the same cross section dimensions and reinforcing as the external footing, so that the centre to centre spacing of thickenings is always less than 17.0 m.” MINISTRY OF BUSINESS, INNOVATION AND EMPLOYMENT 28 JULY 2025 Page 11