CSI Section 06 40 00: How to Read Millwork Specifications

On commercial projects, millwork contractors receive a drawing set from the architect and a project manual containing specifications. The drawings tell you what to build. The specifications tell you how to build it — the grade, the materials, the finishes, the hardware, and the process for getting your shop drawings approved. Skipping a careful read of Division 06 before producing a single sheet is how shops end up fabricating to the wrong standard.

CSI MasterFormat is the organizational system behind those specs. Understanding how it works lets you find the sections that govern your scope, interpret the requirements correctly, and identify conflicts early — before they become costly RFIs or rejected submittals.

What CSI MasterFormat Is

CSI stands for the Construction Specifications Institute. MasterFormat is the numbering system CSI publishes to organize construction specifications consistently across all project types. Every section of a project manual follows the same structure: a six-digit number, a section title, three standard article types (General, Products, Execution), and standardized language that architects and specifiers can customize.

The benefit to millwork contractors is predictability. Once you know the system, you know exactly where to look for your scope on any commercial project — regardless of the architect or project type.

Division 06 — Wood, Plastics, and Composites

All wood-related construction specifications live in Division 06. The subsections most relevant to millwork work are:

• 06 10 00 — Rough Carpentry: Blocking, backing, wood framing. Not millwork scope, but relevant because blocking requirements in this section directly affect where your millwork can be anchored.
• 06 20 00 — Finish Carpentry: Pre-manufactured millwork, running trim, standard casing. Covered here are items that don't require shop drawings — standard off-the-shelf products.
• 06 40 00 — Architectural Woodwork: Custom millwork, casework, paneling, and architectural woodwork that requires shop drawings. This is the section that governs fabrication shops.
• 06 41 00 — Architectural Wood Casework: A subsection of 06 40 00 used on projects where the architect wants to separate casework scope from other custom woodwork.
• 06 46 00 — Wood Trim: Sometimes broken out separately for projects with complex trim profiles or custom millwork profiles distinct from the casework scope.

The exact section breakdown varies by project. Some specifiers write all millwork scope into a single 06 40 00 section. Others break it into multiple subsections. Check the project manual's table of contents first to understand how scope is divided before reading individual sections.

The Three-Part Section Structure: General, Products, Execution

Every CSI section is organized into three parts. Knowing what lives in each part prevents you from missing requirements.

Part 1 — General covers administrative requirements: who is qualified to do the work, what submittals are required, how long the architect has to review them, what samples must be provided, and any mock-up requirements. The submittal schedule in Part 1 will tell you exactly which items require shop drawing submittals and which require only product data. Read this part before scoping your drawing package.

Part 2 — Products specifies materials, components, and fabrication standards. This is where the AWI quality grade is stated, substrate requirements are defined, finish systems are specified, and hardware is listed — either by performance standard or by catalog number. It also covers material sourcing restrictions, such as requirements for FSC-certified wood or low-VOC finishes under LEED projects.

Part 3 — Execution covers field installation standards: tolerances, fastening methods, surface preparation, and the standard of finish required at handoff. It also specifies protection requirements during and after installation, and touch-up procedures for the punch list phase.

AWI Quality Grades — The Most Critical Spec Requirement

The most important thing to extract from Part 2 is the AWI quality grade. The Architectural Woodwork Institute publishes three grades — Economy, Custom, and Premium — that govern fabrication tolerances, joint construction methods, surface preparation, and finish quality. For a full breakdown of what each grade requires, see our AWI millwork standards guide.

The specification may state the grade globally ("All millwork shall be AWI Custom grade unless otherwise noted") or per item ("Reception desk: AWI Premium; storage cabinets in utility rooms: AWI Economy"). If the spec is silent on grade, the default is AWI Custom — but confirm with the architect via RFI before proceeding, because "silent spec" assumptions are a common source of disputes.

The grade designation must appear on your millwork shop drawings. Architects reviewing submittals look for it on the cover sheet or in the title block. A drawing package that doesn't call out the AWI grade will typically get returned with a comment requesting it.

Substrate Requirements

Part 2 of the spec will define what substrate is acceptable — sometimes explicitly, sometimes by reference to AWI standards. The main substrates used in architectural woodwork are:

• MDF (Medium Density Fiberboard): Dimensionally stable, machines cleanly, takes paint-grade finishes well. Standard substrate for paint-grade casework under AWI Custom grade. Not suitable for high-moisture environments without moisture-resistant formulation (MRDF).
• Particleboard: Lower cost, heavier than MDF, adequate for Economy grade painted casework with limited moisture exposure. Not suitable for Premium grade work under most AWI requirements.
• Hardwood plywood: Required for stain-grade face frames, veneer panel doors, and structural components requiring edge fastening. AWI Premium grade typically requires plywood over particleboard for case bodies.
• Solid wood: Used for face frames, door and drawer fronts (stain-grade), molding profiles, and edge banding. Species must match the spec — if the spec says "hard maple," substituting poplar (even though it's also paint-grade) requires written approval.

If the project has a LEED or sustainability requirement, Part 2 may also specify that substrates must be CARB Phase 2 compliant (limiting formaldehyde off-gassing), or that wood must come from FSC-certified sources. Both requirements affect procurement and must be documented in the submittal.

Finish System Requirements

Finishes on architectural woodwork are specified in Part 2 and typically reference AWI finish system numbers (e.g., AWI System 5 — opaque, catalyzed lacquer; System 9 — transparent conversion varnish). The spec may also call out specific characteristics:

• Sheen level: Flat, matte, satin, semi-gloss, or gloss — stated as a percentage, e.g., "60-degree sheen not to exceed 35."
• Color: Usually referenced to a paint system (Benjamin Moore, Sherwin-Williams) with a specific number, or to a Pantone color for custom matches.
• UV resistance: Required on millwork receiving direct sunlight — the spec may call for UV-resistant topcoats in lobbies or exterior-adjacent areas.
• VOC limits: LEED projects specify maximum VOC content for finishes, typically citing California Air Resources Board (CARB) limits or the Green Seal standard.

Field-applied finishes — where the painter applies finish after installation — are sometimes specified instead of shop-applied finishes. When this is the case, Part 3 of the spec will describe the surface preparation standard expected at handoff: typically filled, sanded, and primed, with specific grit requirements.

Hardware in the Spec

Millwork hardware is specified one of three ways in commercial project manuals:

1. Catalog numbers: The spec lists a specific manufacturer, model, and finish. Example: "Blum Tandem Plus Blumotion 563H drawer slide, full extension." No substitutions unless the spec allows "or approved equal." If the specified product is discontinued or unavailable, submit an RFI before selecting an alternative — don't substitute silently.

2. Performance specifications: The spec defines minimum performance requirements (load rating, extension type, number of cycles) without naming a specific product. You select a compliant product and document the compliance in your submittal.

3. "By others" or "NIC" (Not In Contract): The spec explicitly excludes hardware from the millwork scope, meaning another contractor furnishes and installs it. Common for keyed locks in commercial security systems. Verify this in the spec before your scope meeting — missing this distinction is a common source of cost disputes at the end of a project.

Hardware schedules in the shop drawings must cross-reference the spec. If the spec names a product and you've used it, note the catalog number in the hardware schedule so the reviewer can verify compliance without having to look it up separately. This reduces review time and revision cycles — see our guide on what every millwork drawing set must include for the full hardware schedule format.

Submittal Requirements — Part 1 in Detail

Part 1 of the spec defines exactly what you need to submit before fabricating. The most common submittal requirements for millwork are:

• Shop drawings: Required for all custom millwork. The spec will state the scale requirements, what views are needed, and how many copies (if physical) or what PDF format is required.
• Product data: Cut sheets for manufactured components — hardware, glass, specialty materials. Must be submitted with the shop drawings or in advance.
• Samples: Finish samples (stained wood or painted panels at the specified sheen), hardware samples (a physical example of the specified pull, hinge, or slide), and sometimes material samples (a piece of the specified veneer or laminate).
• Fabricator qualifications: If the spec requires AWI QCP certification, you submit the certificate. If it requires proof of experience (e.g., "minimum five years of experience producing commercial AWI Custom grade millwork"), you submit a reference list.

Review time is also stated in Part 1. Most commercial specs allow the architect 10–14 business days for initial review. Factor this into your fabrication schedule from day one — not after GC starts asking why drawings haven't been submitted.

Mock-Up Requirements

High-specification projects — custom hotel lobbies, corporate headquarters, premium retail — often require a full-scale mock-up of a representative millwork unit before full production approval is granted. The spec will state:

• What unit or item must be mocked up (e.g., "one typical base cabinet unit," "reception desk transaction counter section")
• Where the mock-up is to be located (at the shop, at the project site, or at a dedicated mock-up room)
• Who must review and approve the mock-up (architect, owner, interior designer)
• What happens to the mock-up after approval (demolished, incorporated into the final installation, retained for reference)

Mock-up requirements add real time and cost to a project. If you don't see them in your estimate, they need to be flagged as a scope addition at the pre-construction meeting — not discovered after fabrication has started.

Performance Spec vs. Prescriptive Spec — and Substitution Requests

A prescriptive specification names specific products and manufacturers. A performance specification defines what the product must do (load capacity, cycle count, finish durability) without naming who makes it. In practice, most commercial specs combine both: a "basis of design" manufacturer is named, and the phrase "or approved equal" indicates that alternatives may be submitted.

"Or approved equal" is not a blank check. To substitute a different product, you must submit a substitution request demonstrating that the proposed product is equal in all specified performance criteria. The architect evaluates the request and either approves or rejects it. Substitution requests submitted after the submittal deadline — or without adequate comparison documentation — are routinely rejected.

When you identify a material or hardware item that is specified but difficult to source, or that has a long lead time, submit the substitution request early and in writing. Don't wait for the shop drawing review to surface the problem.

Flagging Spec Conflicts Early

After reading Division 06, compare the spec requirements against the architectural drawings. Common conflicts to look for:

• The spec calls for AWI Premium grade, but the drawings show details that are only achievable at Custom grade dimensions
• The spec requires a specific veneer species on a surface that the drawing leaves unspecified
• The spec references a hardware schedule that doesn't exist in the drawing set
• The spec requires field verification of dimensions, but construction is already behind schedule and field conditions aren't available
• The drawing shows a counter depth that conflicts with the ADA clearances implied by the spec's reference to ADA Standards

Each conflict is a candidate for an RFI. Submit these early — before you've drawn the detail in question — so that the architect's response can inform your drawing rather than requiring a revision after the fact. See our step-by-step submittal process guide for how the full review workflow connects to the spec requirements covered here.