Excavated Basement Building Codes & Rules

- Excavated Basement Tools™ simplifies the National Construction Code (NCC) with interactive graphics, including deemed to comply & best practices.

Floor system

Sand Blinding

Sock

Vapour Barrier

Free draining backfill

Filter Fabric

Drainage Cell

Free draining bed

AS/NZS 3500.3:2021, L

Agg Drain^{AS/NZS 3500.3:2021, L}

Slotted PVC preferred
Clean out at high points
No lower than base of footing
Gravity connection to stormwater or sub-floor drainage / pump out sump
Separate from roof or other stormwater systems

Agg Drain

Fall

AS/NZS 2890.1:2004, 2.4.6.2

1 : 200^{AS/NZS 2890.1:2004, 2.4.6.2}

Stormwater Pit

Heel guard type if subject to foot traffic

1 : 300

Reinforced Wall

Fall to Pit

Cover Angle (optional)

Lining a Habitable Room

H3 Timber Battens where in contact with wall
Insulation that won't hold moisture
Foam or Rigid board type
Fibre-cement lining to resist flood damage

Membrane

Protection Board

Cavity Closer

DPC / Flashing

Fall

Industry Recommendation, -

100^{Industry Recommendation, -}

Gravel

Water Bar

1 : 100

Fall

Finished Ground

≥ 150mm^[1] to earth
≥ 75mm^[2] to hardstand
≥ 50mm^[3] to sheltered hardstand

DPC Ground CLEARANCE

NCC 2022 V2

All Building Classes

NCC 2022 HP 5.7.4 [2019: 3.3.5.8]

May 2023

NCC 2022 HP, 5.7.4 (2) (d) (i)

NCC 2022 HP, 5.7.4 (2) (d) (ii)

NCC 2022 HP, 5.7.4 (2) (a)

NCC 2022 HP, 5.7.4 (2) (b)

NCC 2022 HP, 5.7.4 (2) (c)

Building elements in Wet Areas to be Waterproof or Water-resistant to NCC
Flashing & Damp-proof Courses installation clearances
≥ 150mm^{NCC 2022 HP, 5.7.4 (2) (d) (i)} above soft Landscaping
≥ 75mm^{NCC 2022 HP, 5.7.4 (2) (d) (ii)} to Hardstand or Landscaping that grades away from building
≥ 50mm^{NCC 2022 HP, 5.7.4 (2) (a)} to Sheltered Hardstand that grades away from building
DPC installation clearances in Low Rainfall Intensity Areas
≥ 15mm^{NCC 2022 HP, 5.7.4 (2) (b)} above any surface
≥ 0mm^{NCC 2022 HP, 5.7.4 (2) (c)} to Sheltered Hardstand that grades away from building

NCC 2022 HP, 5.7.4 (2) (a)

NCC 2022 HP, 5.7.4 (2) (b)

NCC 2022 HP, 5.7.4 (2) (c)

≥ 150mm^{NCC 2022 HP, 5.7.4 (2) (a)} to earth
≥ 75mm^{NCC 2022 HP, 5.7.4 (2) (b)} to hardstand
≥ 50mm^{NCC 2022 HP, 5.7.4 (2) (c)} to sheltered hardstand

Finished External Surface Fall

Surface Water Drainage RULES

NCC 2022 V1

Class 1 & 10

NCC 2022 HP 3.3.3 (a)

May 2023

NCC 2022 HP, 3.3.3 (a)

NCC 2022 Vol 2, H2P1

NCC 2022 Vol 2, H2D2

Rainwater Management & Drainage to the NCC requirements^{NCC 2022 HP, 3.3.3 (a)NCC 2022 Vol 2, H2P1}
Slope of the Ground Adjacent to the Building^{NCC 2022 Vol 2, H2D2}
Low rainfall areas or Impermeable surfaces (e.g. concrete or paved)
≥ 25mm fall over the first 1m
General requirement for all Other Cases
≥ 50mm fall over the first 1m

Slab Edge Rebate

50mm set down
Internal drainage
Gravel guard

Perimeter WATERPROOFING

NCC 2022 V1

50mm set down
Internal drainage
Gravel guard

Excavation

Unretained embankment to Slope Ratio table with ≤ 2m^[1] depth or height limitation
Cut or fill must be within site allotment^[2]

Earthworks & Retaining

NCC 2022 V2

Class 1 & 10

NCC 2022 3.1 [2019 3.1]

May 2023

NCC 2022 HP, 3.2.1 (1) (c)

NCC 2022 HP, 3.2.1 (1) (a)

Unretained embankment to Slope Ratio table with ≤ 2m^{NCC 2022 HP, 3.2.1 (1) (c)} depth or height limitation
Cut or fill must be within site allotment^{NCC 2022 HP, 3.2.1 (1) (a)}