Cleanroom Design and Construction: The Process

Cleanroom design and construction starts with the classification your process needs, then engineers the HVAC/HEPA, pressure cascade, and personnel/material flow around it – the room is built to hold the grade, not just to look clean. Paul Industries designs, builds, and commissions GMP cleanrooms as a single-source partner.

The design-and-build sequence

1. Classification: set the ISO/GMP grade from the process
2. HVAC/HEPA design: air changes, filtration, pressure cascade, monitoring
3. Flow & layout: gowning, airlocks, material/personnel paths
4. Construction: modular walls/ceilings, flooring, utility integration
5. Commissioning: certification and as-built documentation

Why single-source construction matters

When the HVAC, the shell, and the process utilities are built by different firms, the room often fails to hold its grade at the seams. A single-source builder coordinates all of it – so the finished room certifies the first time.

Related: Cleanroom construction · How to choose a cleanroom company · Cleanroom classes · Request a quote · ISO 8 Cleanroom Requirements · Cleanroom Upgrades and Retrofits in an Operating Facility

Standards referenced: ISO 14644-1 · ASME BPE · 21 CFR 211 · EU GMP Annex 1 (EudraLex Vol. 4)

Walkable ceiling vs suspended grid in a classified space

The ceiling decision is made early, is difficult to reverse, and changes how the room is maintained for its whole life.

A suspended grid carries filters and lights in a lay-in system, with service access from below. It is lighter, cheaper and quicker to install, and it suits rooms at less strict classes where filter changes are infrequent and there is little above the ceiling. Its weakness is that every service visit happens inside the classified space: a filter change, a light fitting, a sensor replacement all bring a technician, a ladder and a tool bag into a room that then has to be cleaned and, depending on what was disturbed, requalified.

A walkable ceiling is a structural deck that supports personnel above the room. Filters, light fittings, ducts and terminal boxes are reached from the interstitial space, so routine maintenance happens without entering the clean side. It costs more, needs greater floor to floor height, and requires the structure above to take the load. It earns that back on aseptic and containment work, where entry to the room is the thing you are trying to minimise and where a filter change that does not break the envelope is worth a great deal.

Ceiling height is the constraint that usually decides it. Where the available height cannot carry both the interstitial space and the room, the grid is the only option, and that trade has to be made at concept stage rather than during construction.

What the envelope choice costs per square foot

Wall and ceiling systems are the most visible line in a cleanroom build and rarely the largest, but the spread between options is wide. Our published figures put cleanroom rated insulated metal panel at $22 to $34 per square foot installed, a modular cleanroom wall system at $45 to $85 per square foot, and stick built drywall with an epoxy coating at $18 to $32 per square foot.

Read those against how the space will be used rather than against first cost alone. Insulated metal panel gives a durable, cleanable, flush finish and suits a permanent GMP facility. A modular system costs the most per square foot and buys speed and the ability to reconfigure or relocate later. Drywall with epoxy is the cheapest to erect and the hardest to maintain over years, because every impact, fixing and service penetration becomes a repair to a coated surface. The component shares behind these figures are on our cleanroom cost guide.

What to require in the construction documents for a classified space

A cleanroom fails certification at the seams, and the seams are drawn in the construction documents. These items belong there.

• A penetration schedule listing every duct, pipe, conduit, sprinkler and cable crossing the envelope, with the sealing detail named for each.
• Corner, junction and coving details drawn rather than noted, including where the wall system meets the floor, the ceiling and any dissimilar system.
• Door schedule stating swing direction relative to pressure, seal type, vision panel detail and whether the door is interlocked.
• Flooring specified with the substrate preparation, moisture test requirement and the coving height at the wall junction.
• Pressure cascade shown as a diagram with a value at every space, including corridors and airlocks, rather than described as positive to adjacent areas.
• Filter locations, sizes and access method marked on the reflected ceiling plan, with the intended change route drawn.
• Material and personnel flow drawn as arrows on the layout, with the airlock sequence identified and gowning steps located.
• A finish schedule naming cleaning and disinfection agents each surface must tolerate, since a surface that cannot survive the disinfectant regime will fail within a year.
• Construction phase cleanliness protocol written into the specification, covering site protection, temporary filtration and the clean build sequence.
• Commissioning hold points placed before concealed work is closed, so envelope integrity and duct cleanliness are proven while they can still be reached.

Frequently asked questions

What does cleanroom design and construction involve?

It spans concept engineering, airflow and pressurization design, HVAC and HEPA filtration sizing, wall, ceiling, and floor systems, utility integration, construction, and ISO 14644 validation. Paul Industries self-performs this full arc as one contractor, so the design intent carries cleanly through to the qualified room.

What comes first in cleanroom design?

Design starts with the process: the product, its required ISO class, personnel and material flows, and the equipment. From that, engineers set the pressure cascade, air change rate, filtration, and layout. Getting the process requirements right first prevents costly redesign during construction.

How is airflow designed in a cleanroom?

Airflow design chooses between unidirectional (laminar) flow for the cleanest zones and turbulent, well-mixed flow for less critical areas. The design sets air change rates, HEPA coverage, and return paths so contamination is swept away from the product and the room holds its ISO class in operation.

What is a pressure cascade and why does design need it?

A pressure cascade keeps cleaner rooms at higher pressure than adjacent dirtier ones, so air always flows outward from the most critical space. Design establishes the differentials, typically 10 to 15 pascals between grades, and the airlocks that maintain them during personnel and material transfers.

How do you design personnel and material flow in a cleanroom?

Good design separates people and materials into unidirectional paths with gowning rooms, airlocks, and pass-throughs that prevent clean and dirty streams from crossing. Flow design is as important as the walls, because most contamination enters with operators and incoming materials.

What wall and ceiling systems are used in cleanroom construction?

Options include modular hardwall panels, softwall curtains, and built-in-place systems, with walkable or non-walkable ceiling grids carrying HEPA filters and services. Paul Industries selects the system based on ISO class, washdown needs, durability, and future flexibility rather than a single default.

How does cleanroom design account for the HVAC load?

HVAC design sizes the air handlers, cooling, humidity control, and filtration to deliver the required air changes while managing the heat from equipment and lighting. Under-sizing the HVAC is a leading cause of rooms that cannot hold their class, so it is engineered against the real load.

What standards govern cleanroom design and construction?

ISO 14644 governs classification, monitoring and the test methods used to prove both. EU GMP Annex 1 applies additionally where sterile product is supplied into Europe, and it is materially more prescriptive, requiring a documented contamination control strategy covering the facility as a whole. The quality framework is 21 CFR 211. Where process services penetrate the envelope, ASME BPE and the USP water monographs come into play, and those penetrations are usually where classification problems originate.

How long does cleanroom design and construction take?

A small ISO 7 suite can be designed and built in weeks, while a large multi-room aseptic facility runs several months, driven by long-lead HVAC and filtration equipment and the validation scope. Paul Industries sets the schedule after the design and equipment lead times are known.

Should design and construction be handled by the same company?

Splitting them creates gaps where the designer’s intent is lost during construction. Paul Industries integrates design and construction under one contract, so the team that engineered the airflow and pressurization also builds and validates it, preserving the design through to qualification.

How does design plan for future flexibility?

Forward-looking design uses modular panels, spare HVAC and filtration capacity, and accessible utility routing so the room can be reconfigured or upgraded to a cleaner class later. Paul Industries can build in this headroom when an owner anticipates changing products or scaling up.

What role does flooring play in cleanroom design?

Flooring must be seamless, cleanable, chemical-resistant, and often static-dissipative. Poured epoxy, welded sheet vinyl, and specialized systems each suit different classes and washdown regimes. The choice affects both cleanliness performance and long-term maintenance, so it is specified deliberately in design.

How is lighting designed for a cleanroom?

Cleanroom lighting uses sealed, flush, cleanable fixtures that do not shed particles or disrupt airflow, integrated into the ceiling grid alongside HEPA filters. Fixture placement is coordinated with the filter layout and return paths so light levels are met without compromising the airflow design.

How does construction protect the eventual ISO class?

The build sequence uses managed materials, sealed penetrations, staged cleaning, and progressive commissioning so the room reaches its ISO class cleanly. Contamination embedded during sloppy construction resurfaces in particle counts, so Paul Industries builds toward the class from the start.

Does cleanroom design include the validation plan?

Yes. Good design defines how the room will be qualified, including sample locations, acceptance criteria, and the commissioning and IQ/OQ/PQ approach. Paul Industries designs with validation in mind, so construction produces a room that can be documented as meeting ISO 14644 and cGMP.

How do I begin a cleanroom design and construction project?

Start with what will happen in the room rather than the class you think you need, because the second frequently changes once the first is clear. Then establish the shell constraints early: floor-to-floor height for ductwork above the ceiling, available shaft space and air handling capacity, floor loading, and any landlord limit on roof plant. Those bind before cleanroom design does, and discovering the shell cannot carry the plant an ISO 7 suite needs is a redesign rather than an adjustment.

How does cleanroom design and construction work?

As a sequence where each stage constrains the next. Define the process and its classification requirement. Establish the pressure cascade across the whole suite, not room by room, since adding one room changes its neighbours. Size air handling for the chosen air change rate, which drives plant space and shaft requirements. Design the envelope and penetrations around that. Then build, balance, certify and qualify, with commissioning treated as a scheduled program rather than a closeout activity.

What is the first step in cleanroom design?

Deciding whether you need a classification at all, and if so which. That single decision drives air change rate, which drives fan capacity, duct sizing, filter area, plant room space and the energy the room consumes for its entire life. A great deal of laboratory, quality control and pilot space needs stable temperature, humidity and contamination control without any formal class, and an unclassified controlled environment costs roughly half an ISO 8 room and carries no recurring certification.

Who should build a cleanroom?

A contractor who owns the performance through to a signed certificate, rather than one who installs panels well. A general contractor can build the shell, but classification is judged on behavior, not finish: a room can be beautifully constructed and still fail because of leakage at the ceiling grid, penetrations sealed untested by another trade, or an air balance that holds at rest and not in operation. Ask who designs the cascade, who balances, and who signs the certificate.

Do you design and build cleanrooms?

Yes, envelope and mechanical construction, pressure cascade design across the suite, air balancing, and certification to ISO 14644 including recovery and envelope integrity testing. We also handle the process services that penetrate the envelope, which is where cleanroom projects most often fail, since every water point of use, clean steam line and CIP connection is both a classification risk and a cascade risk. Crews stay through balancing and certification rather than handing those to a third party.

What does the design phase of a cleanroom need to settle first?

The classification and occupancy state, the process flow through the space, the material and personnel routes, and the pressure regime. Everything mechanical follows from those four, and changing any of them after the air handler is ordered is expensive.

How are material and personnel flows separated?

With separate entry routes and airlocks, so that people and materials do not cross and so that clean and used material do not share a path. Flow design is decided on the layout drawing and is almost impossible to correct after construction.

What is the sequence of a cleanroom construction project?

Design and classification, permitting, long-lead mechanical procurement, building preparation, wall and ceiling erection, mechanical and electrical fit-out, sealing and finishing, balancing, then certification and qualification. Balancing before the room is sealed produces results that do not hold.

What is commissioning versus certification on a cleanroom?

Commissioning proves the systems were installed and set up correctly. Certification tests the room against ISO 14644 for particle count, airflow, filter integrity, pressure and recovery. Certification on an uncommissioned room usually fails on airflow uniformity.

Who should hold the interface between the building and the cleanroom?

One party, because the recurring failure is the gap between the general contractor's building and the cleanroom vendor's room, where penetrations, slab flatness, structure and utilities meet. Unowned interfaces are where cleanroom projects lose their schedule.

How does pharmaceutical cleanroom design differ from an electronics cleanroom, and what does design-build change?

Pharmaceutical cleanroom design is driven by microbial control and regulatory review as much as by particle counts: unidirectional personnel and material flows, a pressure cascade from the cleanest room outward (or inward, for containment), gowning and airlock sequences, cleanable finishes that survive sporicides, and documentation the FDA or EU inspector will read. An electronics cleanroom is designed for particle control and often uses different pressures, raised floors and materials. In a layout, cleanroom design should start from the process flow diagram and the gowning sequence and then size the mechanical system; a cleanroom design build contract puts the designer and the builder under one agreement so that these decisions are made once, by the party that will be responsible for the room passing certification.

What decides whether a cleanroom passes certification?