Does the ADA cluster rule apply to a single unit on a construction site?

The ADA cluster rule does not apply to a single unit on a construction site. The rule requires that when multiple portable toilets are clustered at one location, at least 5 percent of the units (and at least one) must be an ADA-compliant unit. A single unit is not a cluster, so the rule does not mandate that it be accessible. However, you must still comply with OSHA's construction sanitation standard. OSHA 29 CFR 1926.51 requires one toilet for 20 or fewer workers and one toilet seat and one urinal per 40 workers for 20 to 199 workers. With 30 to 40 workers, you need at least one toilet, which you have, but adding a portable urinal would help meet the per-40-worker urinal requirement and reduce strain on the single unit. For a crew that size using one standard unit five days a week, weekly service is the minimum; you should expect to increase service frequency if the unit becomes full or unsanitary before the next scheduled visit. The right call is to keep the standard unit for now, but consider adding a urinal to improve compliance and crew comfort.