The cleanroom construction protocol, start to finish

A cleanroom construction protocol is the order the work happens in, plus the controls that hold at each boundary between one phase and the next. It runs from a green field to a certified room with a process running in it. One rule governs the whole sequence: all dirty work finishes before the envelope closes. Coring a slab after the ceiling is sealed is the most expensive correction in cleanroom construction, and it is a scheduling failure rather than a cleaning failure.

ISO 14644-4:2022 is the governing document for cleanroom design, construction and start-up. Its second edition cancels and replaces the 2001 edition, and it is restructured into normative sections covering requirements, design, construction and start-up, each supported by an informative annex. It applies to new, refurbished and modified installations. The staged protocol below is industry convention and CRM's own practice: the standard sets the frame, the project sets the detail.

Six phases, in order.

1. Dirty construction. Structure, framing, rough mechanical and electrical work, coring, drilling and cutting all happen here under ordinary construction housekeeping, and all of it finishes before the envelope is sealed.
2. Clean-build transition. The envelope closes and protocol tightens: entry controls at every door, wet cleaning in place of dry sweeping, an enforced materials list, dust-generating work moved out of the zone or captured where it is made, and temporary filtration holding the zone at positive pressure.
3. Clean build. Finishes, ceiling grid, wall panels, flooring and final terminations go in while every item entering the zone is inspected at the boundary, only badged and educated people work inside, and particle counts are taken daily as a diagnostic.
4. Final filters, superclean and certification. The final filters are installed, the room gets a full top-down superclean, and the commissioning and certification battery establishes the as-built baseline.
5. Tool hook-up and move-in. Process equipment arrives, is conditioned and wiped down at the boundary, is moved in and placed, and the room is re-tested as it lands, which is the at-rest state.
6. Handover. The certification report, the as-builts and the project logs change hands, and the room moves from a build under protocol to a facility under a cleaning and certification program.

Phase 1: Dirty construction

Everything that makes gross debris belongs here. Structure, framing, rough mechanical, electrical and plumbing, coring, drilling, cutting and grinding. Housekeeping is ordinary construction housekeeping and there are no material restrictions yet, because there is nothing clean to protect.

What this phase owes the rest of the project is completeness. Once the envelope is sealed, reopening it to core a wall or a slab means breaking a clean boundary and paying for the recovery on top of the work itself. CRM crews are trained and qualified in aerial lift operation and fall protection, which is what lets the high work finish on the dirty side of the boundary instead of being deferred into a zone that has already tightened.

Phase 2: Clean-build transition, when the envelope closes

The envelope is sealed. From this point the protocol tightens and stays tight, and the controls that switch on at this boundary are, by category: entry controls at every door, a daily cleaning and debris routine that replaces dry sweeping, an enforced list of prohibited materials, cutting and grinding either moved out of the zone or captured where it is made, and temporary filtration holding positive pressure as early as the air system allows.

Those controls are the whole subject of their own article, and this one hands them over rather than restating them: keeping a cleanroom clean while you build carries the materials list, the entry and cleaning routine, and how each control is enforced day to day.

Phase 3: Clean build

Finish materials, ceiling grid, wall panels, flooring and the final mechanical and electrical terminations go in. Three controls carry this phase and they are the specificity CRM actually brings to a jobsite. Every item entering the zone is inspected, wiped down and de-cartoned at a staged boundary, with non-conformities marked rather than quietly accepted. Access runs through a maintained badge log, and a badge issues only after classroom education, because a trade that has never worked in a clean zone does not know why the rules are what they are. Multi-point particle counts are taken daily.

Those daily counts are diagnostic. They say which trade or which activity is loading the room, on the day it happens, while there is still time to correct it. They are not a compliance record and nothing is certified off them.

Gowning is progressive through this phase, from shoe covers and coats early to full coverall, hood and gloves as the zone approaches operational cleanliness. The badge mechanics, the inspection routine and the count procedure are all carried in depth by keeping a cleanroom clean while you build.

Phase 4: Final filters, superclean and certification

The final HEPA or ULPA filters replace the temporary and roughing filters that carried the build. Then the room gets a full top-down superclean, ceiling to floor in strict order, and only after that do commissioning, balancing and the certification battery run.

The superclean is a milestone, not a housekeeping pass, and it has an order of operations of its own that the top-down supercleaning checklist sets out step by step.

Certification at this point establishes the as-built baseline: the room proved with the construction finished, before equipment and before people. It is the first number the facility will be measured against for the rest of its life, which is why it is worth arriving at it with the logs already written.

Phase 5: Tool hook-up and move-in

Process equipment enters under a sequence of its own, and it is the most procedural part of the protocol: dock arrival, temperature and humidity control applied, wipe-down at the boundary, move-in, then final wipe-down and placement. The conditioning step is the one that gets skipped. Cold equipment entering a conditioned space condenses, and condensation is a corrosion problem and a microbial one at the same time.

That sequence is written out step by step, with the reason for each step, in tool move-in, step by step.

The room is re-tested as equipment lands, which is the at-rest occupancy state. Operational certification follows once the process runs with staff present.

Phase 6: Handover

The project ends with paper: the certification report, the as-builts, and the cleaning and non-conformity logs the build generated. What changes at handover is the regime rather than the room. A room under construction protocol is being brought to a standard; a room in operation is being held at one, which means a scheduled cleaning program and a certification schedule from here on.

The handover is also the cheapest moment to write the maintenance regime, because the people who held the protocol through the build already know where the room loads, which entries take the traffic, and which activities moved the counts.