Downpipe Building Codes & Rules
- Explore essential downpipe installation tips, from proper sizing and slope to ensuring safety and durability, with expert advice for contractors and designers.
Clear of
Flashing
Downpipes - RCC Requirement
- 2mm thk & 114.3mm OD
- Stainless steel
- Straight, turn down into Outlets
- ≥ 2hr Hydrostatic Test
HB 39:2015, 5.3.2 (k)
AS/NZS 3500.3:2018, 4.7.2.3
HB 39:2015, 5.7.7 (b)
HB 39:2015, 5.7.7 (a)
HB 39:2015, 5.7.7 (b)
HB 39:2015, 5.7.7 (a)
HB 39:2015, 5.7.6 (h)
≥ 1:25HB 39:2015, 5.7.6 (h)
HB 39:2015, 5.6 (i)
HB 39:2015, 5.6 (a)
Storm Protection
- Backflash or Overflow to prevent Stormwater ingressHB 39:2015, 5.6 (i)
- Baffle Flashings if exposed to high windsHB 39:2015, 5.6 (a)
Eaves Gutter - RCC Requirement
- ≥ 150mm Half Round profile
- ≤ 600mm Bracket spacing
Fall
Fall
HB 39:2015, 5.6
Eaves GutterHB 39:2015, 5.6
- ≥ 1.2m Bracket spacing
- ≤ 20m Expansion Joint spacing
AS/NZS 3500.3:2021, 4.7.2.3
Lap JointsAS/NZS 3500.3:2021, 4.7.2.3
- ≤ 40mm fixing spacing
- Lap in direction of flow
HB 39:2015, 5.6 (k) (iii)
HB 39:2015, 2.9
HB 39:2015, 2.9
Downpipe Connection
- Tapered Outlet to suit GutterHB 39:2015, 5.6 (k) (iii)
- Stitch seal with neutral cure SiliconeHB 39:2015, 2.9
- Colour matched self sealing Pop RivetHB 39:2015, 2.9
Downpipes
- Clear of Window & Door operation & other clearances[1]
- Protect from damage[2]
- ≥ 100mm clear of Electrical or Gas Line[3]
- ≥ 50mm clear of any other service[4]
Downpipe & Accessory MATERIALS
NCC 2022 V4
All Building Classes
NCC 2022 F1P3, F1D3 [2019 FP1.3, F1.1]
May 2023
NCC 2022 HP, 3.3.5
AS/NZS 3500.3:2021, 1
AS/NZS 2179.1:2014, 2.6.1
AS/NZS 2179.1:2014, 2.3.2
AS/NZS 2179.1:2014, 2.3.4 (d)
Informative
- Stormwater Drainage installed to NCC & AS/NZS 3500.3NCC 2022 HP, 3.3.5AS/NZS 3500.3:2021, 1
- Rainwater Drainage Systems must convey Rainwater to an Outfall
- 5% Annual Exceedence ProbabilityAS/NZS 2179.1:2014, 2.6.1
- Percentage chance of a specific rainfall amount (intensity or depth) occurring in a year
- Stainless SteelAS/NZS 2179.1:2014, 2.3.2
- 301, 302 or 304 Grade in Mild to Moderate Environments
- 316 Grade in Severe Industrial, Very Severe Environments
- 305 Stainless or 400 Alloy Fasteners
- Aluminium/Zinc alloy coated steelAS/NZS 2179.1:2014, 2.3.4 (d)
- ≥ AZ150 coating class to AS 1397, or
- Prepainted to AS/NZS 2728
- Grade to Manufacturer's Recommendations to suit environmental exposure
- Class 3 Fasteners
- Zinc-coatedInformative
- ≥ Z275 coating class to AS 1397, or
- Class 3 Fasteners
Bluescope Colorbond GRADES
NCC 2022 V1
AS/NZS 3500.3:2021, 4.5.6 (a) (vi)
AS/NZS 3500.3:2021, 4.5.6 (a) (v)
AS/NZS 3500.3:2021, 4.5.6 (a) (i)
AS/NZS 3500.3:2021, 4.5.6 (a) (iv)
- Clear of Window & Door operation & other clearancesAS/NZS 3500.3:2021, 4.5.6 (a) (vi)
- Protect from damageAS/NZS 3500.3:2021, 4.5.6 (a) (v)
- ≥ 100mm clear of Electrical or Gas LineAS/NZS 3500.3:2021, 4.5.6 (a) (i)
- ≥ 50mm clear of any other serviceAS/NZS 3500.3:2021, 4.5.6 (a) (iv)
HB 39:2015, 5.7.6 (d)
HB 39:2015, 5.6 (f)
AS/NZS 3500.3:2021, 4.5.3 (a)
Spreaders
- ≥ 1.8m beyond spreader[1][2]
- Seal side laps to corrugated Roof Sheets
- Fully sark Tiled Roofs
- Extend foot of DP to keep clear of Flashing[3]
- 1/2 Cap Ends for cleaning[4]
Spreader RULES
NCC 2022 V2
All Building Classes
NCC 2022 3.3.5, F1P3, F1D3 [2019 3.1.3.5, FP1.3, F1.1]
May 2023
HB 39:2015, 5.7.7
HB 39:2015, 5.7.7
HB 39:2015, 5.7.7
HB 39:2015, 5.7.7 (g)
NCC 2022 HP, 3.3.5
AS/NZS 3500.3:2021, 1
- Stormwater Drainage installed to NCC & AS/NZS 3500.3HB 39:2015, 5.7.7HB 39:2015, 5.7.7
- Catchment area of both upper & lower Roof must not exceed Manufacturer's Design Carrying Capacity for the lower Roof
- Water to be discharged in direction of Roof FallHB 39:2015, 5.7.7
- Extend Foot of Downpipe to ensure Spreader is clear of FlashingsHB 39:2015, 5.7.7 (g)
- Must not discharge above ValleysNCC 2022 HP, 3.3.5
- Corrugated Roof SheetsAS/NZS 3500.3:2021, 1
- ≥ 1.8m each side from Spreader to be Sealed at Laps for full sheet length
- Tiled Roof
- ≥ 1.8m each side from Spreader to be Sarked & turned into the Gutter
HB 39:2015, 5.7.7 (a)
HB 39:2015, 5.7.7 (b)
HB 39:2015, 5.7.7
HB 39:2015, 5.7.7 (f)
- ≥ 1.8m beyond spreaderHB 39:2015, 5.7.7 (a)HB 39:2015, 5.7.7 (b)
- Seal side laps to corrugated Roof Sheets
- Fully sark Tiled Roofs
- Extend foot of DP to keep clear of FlashingHB 39:2015, 5.7.7
- 1/2 Cap Ends for cleaningHB 39:2015, 5.7.7 (f)
Eaves Gutter
Impact Protected DP
Stormwater Connection
- Downpipe with Direct Connection[1]
- ≥ 75mm unsealed slip joint
- ≤ 2m from point of entry to Stormwater Drain
- Open Connection[2]
- ≥ 40mm clear above grate
Stormwater Connection TYPES
NCC 2022 V5
All Building Classes
NCC 2022 F1P3, F1D3 [2019 FP1.3, F1.1]
May 2023
NCC 2022 HP, 3.3.5
EFSG 2.0
EFSG 2.0
Informative
- Stormwater Drainage installed to NCCNCC 2022 HP, 3.3.5
- Rainwater Drainage Systems must convey Rainwater to an Outfall & avoid surface water damaging the BuildingEFSG 2.0
- 5% AEPEFSG 2.0
- Percentage chance of a specific rainfall amount (intensity or depth) occurring in a year
- Surface water must not enter the Building
- 1% AEP
- Hardstand & Precast OutletInformative
- EFSG (NSW Public School) compliant
- 30° splayed end
- 40mm clearance
- Screw fixed Grate
- Direct Connection
- Residential / Cottage construction
- Fall Finished Ground away from Building
Outlet SUPPLIERS
NCC 2022 V2
- Suitable Products for this use (equal to's allowed)
- Galvin Engineering Concrete Downpipe Sump Box
- ≥ 150mm Ø Outlet
- Screw fixed Grate
- Others? Please send feedback
HB 39:2015, 5.7.6 (g)
EFSG 2.0
- Downpipe with Direct ConnectionHB 39:2015, 5.7.6 (g)
- ≥ 75mm unsealed slip joint
- ≤ 2m from point of entry to Stormwater Drain
- Open ConnectionEFSG 2.0
- ≥ 40mm clear above grate
Plumbing Overview
Redirecting... (5)