Below-Ground Tanking & Basement Waterproofing SWMS

Below-ground tanking and basement waterproofing is a high-risk construction activity involving the application of cementitious slurries, positive-side sheet membranes, drainage cell, and protection board to excavated basement walls, raft slabs, and lift pits. The work occurs in partially enclosed or fully confined spaces adjacent to unsupported or shored excavations, often in the presence of groundwater ingress, solvent-based primers, and gas-fired torches or hot-air welders. Under WHS Regulation 2025 Part 6.3, this activity is classified High Risk Construction Work because it is performed in or near a confined space, adjacent to excavation deeper than 1.5 m, and frequently involves the use of flammable substances in enclosed atmospheres. A documented Safe Work Method Statement is mandatory before work commences, must be developed in consultation with workers, kept accessible at the workplace, and reviewed if controls are revised or an incident occurs. Failure to prepare and implement a compliant SWMS exposes the PCBU, principal contractor, and supervising officers to enforceable WHS duties and category 1–3 offences.

Hazards identified

7 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Elimination — Specify pre-applied bonded membrane systems installed on blinding before reinforcement and pour, eliminating downstream confined-space and excavation-edge application entirely where design permits.
2. 2Elimination — Sequence works so basement tanking is completed before lift-pit shaft formwork and surrounding services restrict access, removing the confined-space entry requirement for follow-on coats.
3. 3Substitution — Substitute solvent-based bituminous primers with water-based or low-VOC acrylic primers compliant with AS/NZS 4858 to remove flammable-vapour and narcotic-vapour exposure inside the basement envelope.
4. 4Substitution — Replace cementitious slurries containing hexavalent chromium with reduced-chromate cements complying with EN 196-10 limits to eliminate Cr(VI) dermal sensitisation risk.
5. 5Engineering — Install forced mechanical ventilation delivering minimum 20 air changes per hour into lift pits and tanked rooms, with continuous LEL, O2 and VOC monitoring per Confined Space CoP 2021.
6. 6Engineering — Install temporary edge protection to raft slab perimeter and pit penetrations, certified shoring or battered excavation faces to AS 5047, and powered conveyor or hoist for membrane roll handling.
7. 7Administrative — Issue confined-space entry permit, stand-by attendant with two-way comms, atmospheric test log, and SWMS sign-on at every shift pre-start brief; suspend works if LEL exceeds 5%.
8. 8Administrative — Implement hot-work exclusion zone of 6 m from any solvent application, lock out torches and welders during priming, and rotate manual-handling teams every 30 minutes.
9. 9PPE — Supplied-air respirators or full-face A2P2 cartridge respirators for primer application, nitrile chemical gauntlets, Type 5/6 coveralls, chemical-splash goggles, and AS/NZS 2210 safety boots with puncture-resistant midsoles.
10. 10PPE — AS/NZS 1891 compliant full-body harness with dual lanyard and rescue retrieval system anchored above any confined-space entry, plus FR coveralls during any residual hot-work activity.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

On a four-level residential basement project, the waterproofing leading hand arrives at 6:30 am to apply solvent-primed sheet membrane to the lift-pit shaft and southern retaining wall. At the pre-start brief held at the site shed, the crew of three opens this SWMS on a tablet and walks the controls register line by line against today's conditions. The leading hand confirms the lift pit is 2.4 m deep with a single 600 mm access opening, triggering the confined-space entry permit (control 7) and forced ventilation set-up (control 5). The atmospheric monitor is calibrated and lowered; baseline O2 reads 20.9% and LEL 0%. Because the original specification called for solvent primer, the team substitutes the water-based primer already approved in control 3, eliminating the hot-work exclusion zone conflict with grinders running on level above. Each worker signs on against the SWMS, acknowledging the rescue retrieval anchor point and stand-by attendant rotation. Two hours in, the monitor alarms at 6% LEL from a neighbouring trade's adhesive — work is immediately suspended per control 7, the pit is purged, and the SWMS is annotated with the deviation and corrective action before re-entry. The signed document and atmospheric log are filed with the principal contractor at shift end.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• AS 2865 — Confined spaces

Frequently asked questions