Vertical Termination Height Calculator (AS 4654.2)

Introduction

AS 4654.2:2012 sets the minimum vertical upstand for external waterproofing membranes at deck-to-wall, roof-to-parapet and similar terminations. The required height is governed by the design wind speed at the site — the higher the ULS pressure on the membrane edge, the higher the upstand needs to be to keep wind-driven rain from getting behind it.

The tool below takes an Australian address, picks up the wind region from the coordinates, and combines it with the building height and terrain category to give you the site ULS wind speed (V_h,u) and the matching termination band from AS 4654.2 Table A1.

AS 4654.2 Figure 2.8 — typical membrane termination detail at an external door sill, with the vertical upstand dimensioned 'For height, see Table A1, Appendix A' — The number this calculator returns is the vertical upstand labelled *“For height, see Table A1, Appendix A”* in the detail above — how far the waterproofing membrane must turn up above finished floor level at a door sill, deck-to-wall or similar termination. Source: AS 4654.2:2012, Figure 2.8 (in part). © Standards Australia.

Calculate the required upstand

Enter the site address, building height and terrain category.

Site address

Building height h (m)

Mean roof height above ground.

Terrain category

Per AS/NZS 1170.2 Table 4.1.

Aerial view of the site. Check the upwind surroundings (worst direction) and confirm the terrain category below matches what you see — open water, open grassland, suburban or dense urban.

Visual reference of AS/NZS 1170.2 terrain categories TC1 through TC4

Pick the category that best matches the site's upwind fetch (worst direction).

Enter a site address to calculate.

AS 4654.2 Table A1 Bands

The full mapping of AS 4055 wind class to required termination height. The calculator above highlights the active band based on your inputs.

AS 4055 class	ULS V_h,u (m/s)	Termination height (mm)
N1	≤ 34	40
N2	≤ 40	50
N3 / C1	≤ 50	70
N4 / C2	≤ 61	100
N5 / C3	≤ 74	150
N6 / C4	≤ 86	180
> N6 / C4	> 86	Consult engineer

How the Calculation Works

The site ULS wind speed at the building roof height is computed from AS/NZS 1170.2:2021 as:

V_h,u = V_R,500 × M_d × M_z,cat(TC, h) × M_s × M_t × M_c

V_R,500 — 500-year return-period regional wind speed (Table 3.1), based on the auto-detected wind region.
M_d = 1.0 — worst-direction (no direction reduction). Conservative for a single termination-height number.
M_z,cat — terrain/height multiplier (Table 4.1), interpolated between standard heights for the chosen TC.
M_s = M_t = 1.0 — no shielding or topographic benefit assumed.
M_c — climate change multiplier per Table 3.3 (1.05 for B2/C/D, 1.00 elsewhere).
Importance Level 2 — 500-year ARI, standard for habitable buildings.

The resulting V_h,u is then matched against AS 4654.2 Table A1 to give the minimum termination height.

Why This Matters

The default 150 mm upstand widely used as a "rule of thumb" is the N5/C3 band — appropriate for severe wind environments, but often over-specified for inner-suburban Sydney where N2 or N3 conditions are typical. Conversely, sites in coastal cyclonic regions (C/D) can require upstands greater than 150 mm, and a default of 150 mm would be under-specified.

The key point is that a default 150 mm should not be carried blindly onto a drawing. The upstand should be re-derived per project against the site V_h,u — the calculator above is the quickest way to do that.

Scope and Limits

External upstands only. Internal terminations in wet areas are governed by AS 3740 (≥ 150 mm above FFL), independent of wind speed.
Preliminary estimate. Worst-direction M_d, no shielding, no topographic factor. For final design, run a directional AS/NZS 1170.2 assessment with project-specific shielding (M_s) and topography (M_t).
Houses (Class 1/10) can also be classified directly via AS 4055 — the bands above are framed in those terms for cross-reference.

Need a project-specific AS/NZS 1170.2 assessment with directional, shielding and topographic factors? Contact our facade and waterproofing engineers.