B1/AS1: Structural provisions for buildings

B1 STRUCTURE ACCEPTABLE SOLUTION B1/AS1 Buildings and structures b) remove Figure 7.13(A) – Foundation edge details – In situ concrete – Dimensions & reinforcing for single storey; and c) modify the title of Figure 7.13(B) to “Dimensions & reinforcing for 1 or 2 storeys”; and d) remove Figure 7.14(A) – Foundation edge details – Concrete masonry – Single storey e) modify the title of Figure 7.14(B) to “1 or 2 storeys”, and add a note: “for a single storey foundation, 15 Series masonry may be used and the minimum footing width may be 190 mm”; and f) remove Figure 7.15(A) – Masonry veneer foundation edge details – Dimensions and reinforcement for single storeys; and g) remove Figure 7.16 (A) – Masonry veneer foundation edge details – Concrete masonry – Single storey. COMMENT: These modifications to the figures remove the unreinforced and untied slab to footing single storey option. 2.3.7.2 For the design of concrete slab-on-ground slabs: a) in NZS 3604, replace Clause 7.5.8.1 with: i) “Clause 7.5.8.1 All slab-on-ground floors shall be reinforced concrete in accordance with Clauses 7.5.8.3, 7.5.8.4 and 7.5.8.6.4. All reinforcing steel, including welded mesh, shall be Ductility Class E in accordance with AS/NZS 4671.”; and b) where Grade 500E welded steel mesh is specified, it shall meet the requirements of Subsection 3.2.2 of the Building Product Specifications. 2.3.7.3 For ground slab reinforcing, replace Clause 7.5.8.3 of NZS 3604 with: a) “Clause 7.5.8.3 All slab-on-ground reinforcing shall extend to within 75 mm of the outside edge of the slab (including the foundation wall) and shall consist of a minimum 2.27 kg/m2 welded reinforcing mesh sheets (1.14 kg/m2 in each direction), which shall be lapped at sheet joints such that the overlap measurement between the outmost cross wires of each fabric sheet is equal to the greater of one of the following: • the spacing of cross wires plus 50 mm, • 150 mm, or • the manufacturer’s requirements. Slabs shall have a maximum dimension of 24 m between free joints.” 2.3.7.4 For unreinforced concrete slabs, in NZS 3604: a) remove Clause 7.5.8.6.2; and b) replace the title “Figure 7.18 – Irregular slab (plan view) (see 7.5.8.6.2)” with: “Figure 7.18 – Irregular slab (plan view) (see 7.5.8.6.4)”. 2.3.7.5 For polypropylene fibre reinforced slabs, remove Clause 7.5.8.6.3 from NZS 3604. 2.3.7.6 For free joints, add the new clause to NZS 3604: a) “Clause 7.5.8.8 Free Joints. At free joints, slab reinforcement shall be terminated and there shall be no bonding between vertical concrete faces (prevented by using building paper or a bituminous coating). R12 dowel bars 600 mm long shall be placed at 300 mm centres along the free joint and lapped 300 mm with slab reinforcement on both sides of the joint. All dowel bars on one side of the joint shall have a bond breaker applied, e.g. by wrapping dowel bars for 300 mm with petrolatum tape. Joint dowel bars must be installed in a single plane, in true alignment and parallel.” MINISTRY OF BUSINESS, INNOVATION AND EMPLOYMENT 28 JULY 2025 Page 9