New Zealand · Acceptable Solution
B1/AS1: Structural provisions for buildings
Acceptable Solution B1/AS1 for structural provisions within its stated scope under clause B1 of the New Zealand Building Code.
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- Second edition · effective 28 July 2025
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Structure
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B1 STRUCTURE ACCEPTABLE SOLUTION B1/AS1
Buildings and structures
Table 7.4A: Reinforced concrete foundations in expansive soils for light wall claddings
Forming part of the modifications to NZS 3604 for Clause 7.5.13.3.1
Expansive soil class Slightly ‘S’ Moderately ‘M’ Highly ‘H’ Extremely ‘E’
Soil embedment (D ) 375 mm 525 mm 575 mm 625 mm
e
Top steel (A top) 2/D16 2/D16 2/D16 2/D16
S
Bottom steel (A bottom) 1/D16 1/D25 1/D20 1/D25
s
Stirrups R6/125 crs. R6/125 crs. R6/300 crs. R6/300 crs.
Maximum spacings of No internal No internal
2.5 m crs. 2.5 m crs.
internal thickenings thickening thickening
Depth of thickening (D1) – – 400 mm 450 mm
Base width (B1) – – 300 mm 350 mm
Top steel (A top) – – 2/D20 2/D20
S
Bottom steel (A bottom) – – 2/D16 2/D20
s
Stirrups – – R6/150 crs. R6/150 crs.
Table 7.4B: Reinforced concrete foundations in expansive soils for medium wall and heavy wall
claddings
Forming part of the modifications to NZS 3604 for Clause 7.5.13.3.1
Expansive soil class Slightly ‘S’ Moderately ‘M’ Highly ‘H’ Extremely ‘E’
Soil embedment (D ) 500 mm 550 mm 775 mm 800 mm
e
Top steel (A top) 2/D16 2/D20 2/D20 3/D20
S
Bottom steel (A bottom) 2/D16 2/D16 2/D20 2/D20
s
Stirrups R6/125 crs. R6/250 crs. R6/300 crs. R6/300 crs.
Maximum spacings of
– 2.5 m crs. 2.5 m crs. 2.5 m crs.
internal thickenings
Depth of thickening (D1) – 350 mm 450 mm 500 mm
Base width (B1) – 300 mm 300 mm 350 mm
Top steel (A top) – 2/D16 3/D20 3/D20
S
Bottom steel (A bottom) – 2/D16 2/D16 2/D20
s
Stirrups – R6/125 crs. R6/150 crs. R6/150 crs.
MINISTRY OF BUSINESS, INNOVATION AND EMPLOYMENT 28 JULY 2025 Page 13
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