Drug and alcohol testing on residential construction sites (Australia)

What it is

Drug and alcohol testing is the process of sampling a worker's urine, oral fluid or breath to detect substances that impair safe work. On residential construction sites, the legal hook is the primary duty in section 19 of the model Work Health and Safety Act 2011, mirrored in every state and territory except Victoria. That duty requires a person conducting a business or undertaking, including a residential builder, to eliminate or minimise risks to health and safety so far as is reasonably practicable. Impairment from drugs or alcohol is one of those risks.

A builder cannot demand a test just because a worker looks tired or grumpy. Testing must rest on a documented policy, a legitimate safety purpose, the worker's informed consent and a procedure that follows the relevant Australian Standard.

When testing is lawful

Three pathways are accepted in residential building.

Pre-employment testing

A builder can require a negative test before a worker starts on site, provided the offer of employment is conditional on it and the candidate consents in writing. The pre-employment screen catches habitual users before they pick up tools and is the most common entry point for testing on residential sites.

For-cause testing

For-cause or reasonable-suspicion testing is allowed where a supervisor reasonably believes a worker is impaired. Signs that meet the threshold include slurred speech, glazed eyes, unsteady gait, smell of alcohol or unsafe behaviour at height. The supervisor should document what they saw before requesting the test. A single hunch will not survive an unfair dismissal challenge.

Post-incident testing

After a notifiable incident under section 35 of the WHS Act, post-incident testing of the workers involved is generally lawful and expected. Insurers and regulators will ask whether the builder tested. Site policies usually require it within 24 hours.

Random testing remains contested. The Fair Work Commission has upheld it in high-risk industries such as mining and rail, but it is harder to justify on a small residential site. A builder considering random testing should consult workers under section 47 of the WHS Act and document the safety rationale.

The two Standards that matter

Two Standards govern how the test is collected and analysed. Using a method outside these Standards weakens any later disciplinary action.

AS/NZS 4308:2023 covers procedures for the collection, detection and quantitation of drugs of abuse in urine. It sets cut-off concentrations, chain-of-custody rules and laboratory confirmation requirements. Urine testing has a longer detection window (up to several days for cannabis) which catches off-site use that no longer impairs the worker.

AS/NZS 4760:2019 covers the same elements for oral fluid (saliva) testing. Oral fluid detects recent use, usually within hours, so it correlates better with current impairment. Most on-site rapid tests on residential builds use the oral fluid method.

Breath testing for alcohol does not have a dedicated Standard for workplace use but most builders adopt the limits used by police roadside testing, with a typical site cut-off of 0.02 grams per 100 millilitres of blood, or zero for high-risk work such as crane operation and dogging.

Informed consent and procedural fairness

Consent is the keystone. A worker must know what is being tested, who will see the result, how the sample will be handled and what will happen if they refuse. The policy should be in the contract or signed acknowledgement before any test occurs.

What a compliant test looks like

• A trained collector, ideally an external provider
• A private, clean area on site
• A sealed kit with batch numbers recorded
• Split-sample collection so the worker can request a second laboratory test
• Non-negative results sent for confirmation at a NATA-accredited laboratory
• Written results provided to the worker and the builder only

Refusal

A refusal is usually treated as a deemed positive under a well-drafted policy. The Commission has accepted this where the policy was clear, the worker knew the consequences and the refusal was not for a legitimate medical reason. A builder who tries to treat refusal as misconduct without that paperwork in place often loses.

Practical risks

The biggest legal risk is not the test itself but acting on a result without due process. Stand the worker down, await the laboratory confirmation, give them a chance to explain and only then make the disciplinary call. Skipping the confirmation step has cost more than one builder a reinstatement order.