This guide reflects CDF Distributors' standard specifications and field-tested recommendations used by commercial contractors nationwide. The information is provided for specification and selection purposes. Always verify requirements with the Authority Having Jurisdiction (AHJ) for your project location.

For questions or to order a complete door assembly, contact CDF at (855) 769-9895 or sales@cdfdoors.com. Configure your assembly online at ProBuilder: cdfdistributors.com.

About This Guide

What is the difference between a hollow-core and solid-core flush door?

A hollow-core flush door has a honeycomb or mesh core, weighs approximately 15-20 pounds, and provides minimal sound attenuation and no fire rating. A solid-core flush door uses a particleboard, mineral, or stave lumber core, weighs 50-90 pounds depending on core type, and provides moderate to high sound attenuation. Solid-core doors are available with fire ratings from 20 to 180 minutes depending on the core material.

What core type is required for a 90-minute fire-rated flush door?

A mineral core is required for 90-minute fire-rated flush doors. Particleboard and stave lumber cores cannot achieve fire ratings above 20 minutes. Mineral-core construction uses a non-combustible gypsum-based or calcium silicate core that provides 20-minute, 45-minute, 60-minute, 90-minute, and 180-minute fire rating capability.

What face material should I specify for a high-traffic commercial corridor?

High-pressure decorative laminate (HPDL) is the standard face material for high-traffic commercial corridors. HPDL provides high surface durability, stain resistance, and does not require field finishing. For corridors in wet environments, FRP (fiberglass reinforced plastic) faces provide additional moisture and impact resistance.

Are hardboard-faced doors suitable for commercial use?

Yes. Hardboard (HDF) faced flush doors are the most economical commercial-grade option. They provide a smooth, uniform surface designed to be painted on site. Hardboard faces are suitable for interior applications such as offices, corridors, and utility rooms where a painted finish is acceptable and surface abuse is moderate.

Does CDF supply Masonite flush doors?

Yes. CDF Distributors supplies commercial flush doors through its partnership with Masonite Architectural. All core types and face materials are available and can be configured in CDF's ProBuilder tool as part of a complete door, frame, and hardware assembly.

Can a flush door achieve a 180-minute fire rating?

Yes. Mineral-core flush doors with specific construction are available with 180-minute (3-hour) fire ratings. These doors use a denser mineral core and may be limited to specific face materials. The complete assembly (door, frame, hardware) must be tested and listed for the 180-minute rating.

Frequently Asked Questions

CDF's ProBuilder tool lets you configure complete flush door assemblies from Masonite Architectural. Select core type, face material, fire rating, and hardware preparation, with automatic validation of code-compliant combinations. For assistance, call (855) 769-9895 or email sales@cdfdoors.com.

Configure Your Door Assembly

CDF Distributors supplies commercial flush doors through its partnership with Masonite Architectural. Masonite manufactures flush doors in all core types (hollow, particleboard, mineral, stave lumber) and face materials (hardboard, wood veneer, HPDL, FRP) discussed in this guide.

CDF's ProBuilder configuration tool allows specifiers to build complete wood door assemblies by selecting the core type, face material, fire rating, size, and hardware preparation. ProBuilder validates that the selected combination is available and code-compliant. For example, selecting a 90-minute fire rating automatically limits core options to mineral core and validates that the selected face material is compatible with the fire rating.

CDF's Masonite Partnership and ProBuilder Wood Door Options

The specification decision depends on the fire rating requirement, traffic volume, acoustic performance needs, and budget.

• Interior closets, storage (non-rated): Hollow core for economy; particleboard core for moderate durability

• Standard interior office/corridor (non-rated or 20-minute): Particleboard core with hardboard or wood veneer face

• Fire-rated corridors and stairwells (45 to 90 minutes): Mineral core with appropriate face material

• High-traffic or high-abuse (schools, hospitals): Mineral core with HPDL or FRP face

• Wet or corrosive environments: FRP-faced with moisture-resistant core

• Architectural/design-sensitive areas: Wood veneer face with matching stile-and-rail or stave core

• Maximum fire rating (180 minutes): Mineral core with specific manufacturer-listed construction

When to Specify Each Construction Type

Commercial flush doors are available with fire ratings of 20, 45, 60, 90, and 180 minutes. The fire rating indicates the duration the door assembly (door, frame, hardware, and glazing) maintains its integrity during a standard fire test (UL 10C / NFPA 252).

The relationship between core type and available fire ratings is as follows:

• 20-minute rating: Available with particleboard core, mineral core, or stave lumber core. Suitable for corridor and room separation where a 20-minute rating is required by code.

• 45-minute rating: Requires mineral core. Used in 1-hour rated corridor walls (door rating is typically 3/4 of the wall rating).

• 60-minute rating: Requires mineral core. Used in 1-hour rated occupancy separation walls and stairwell enclosures.

• 90-minute rating: Requires mineral core. Used in 2-hour rated walls such as stairwell enclosures, exit passageways, and occupancy separations.

• 180-minute rating: Requires mineral core with specific construction. Used in 3-hour or 4-hour rated walls such as area separation walls and fire barriers in high-hazard occupancies.

Fire Ratings for Flush Doors

The face material of a flush door determines its appearance, durability, moisture resistance, and maintenance requirements.

Hardboard Faces

Hardboard (also called high-density fiberboard or HDF) is a smooth, paintable face material manufactured from compressed wood fibers. Hardboard-faced flush doors are the most economical commercial-grade option and are designed to be painted on site. They provide a uniform, smooth surface without wood grain. Hardboard faces are suitable for interior applications where a painted finish is acceptable.

Wood Veneer Faces

Wood veneer faces use thin slices of natural wood applied over the core with adhesive. Veneer species include birch, maple, oak, cherry, walnut, mahogany, and others. Veneer cuts (rotary, plain sliced, quarter sliced, rift cut) affect the grain pattern and cost. Wood veneer-faced doors provide a natural wood appearance and are finished with stain and clear coat, or opaque paint. They are specified for offices, conference rooms, lobbies, and other spaces where appearance is a priority.

Plastic Laminate (HPDL) Faces

High-pressure decorative laminate (HPDL) faces are factory-applied laminate sheets bonded to the core. HPDL faces provide high surface durability, stain resistance, and a wide range of colors and patterns. They are specified for high-traffic corridors, healthcare facilities, food service areas, and other applications requiring a durable, washable surface. HPDL-faced doors do not require field finishing.

Fiberglass Reinforced Plastic (FRP) Faces

FRP-faced flush doors have a fiberglass reinforced polyester face sheet bonded to the core. FRP provides high moisture resistance, impact resistance, and chemical resistance. These doors are specified for wet environments (commercial kitchens, laundries, car washes, natatoriums), corrosive environments, and areas requiring frequent washdown or chemical cleaning.

Face Materials

The core of a flush door determines its weight, sound attenuation, structural integrity, fire rating capability, and cost. Commercial flush doors use several core constructions, each suited to different applications.

Hollow Core

Hollow-core flush doors have a honeycomb cardboard or mesh core between the face sheets. They are lightweight (approximately 15-20 pounds for a standard 3070 door) and the least expensive flush door construction. Hollow-core doors provide minimal sound attenuation and are not available with fire ratings. They are appropriate for interior closet doors, temporary partitions, and other low-demand applications where cost is the primary consideration.

Solid Particleboard Core

Particleboard-core flush doors use a solid particleboard slab as the core material. These doors weigh approximately 50-60 pounds for a standard 3070 door and provide moderate sound attenuation (STC ratings typically in the 28-32 range). Particleboard core is the standard commercial-grade flush door construction. These doors are available with 20-minute fire ratings and are appropriate for interior office doors, corridor doors, and other standard commercial applications.

Mineral Core

Mineral-core flush doors use a non-combustible mineral composition core (typically gypsum-based or calcium silicate) between the face sheets. Mineral core is required for fire ratings of 45 minutes and above. These doors weigh approximately 70-90 pounds for a standard 3070 door. Mineral-core construction is available with fire ratings of 20, 45, 60, 90, and 180 minutes, making it the required core type for fire-rated openings in stairwells, corridors, and occupancy separations.

The five standard fire rating levels for mineral-core flush doors are: 20-minute, 45-minute, 60-minute, 90-minute, and 180-minute. The required core density and thickness increase with the fire rating duration. At 180 minutes (3 hours), the door construction typically requires a thicker core and may be limited to specific face materials.

Stave Lumber Core

Stave lumber core (also called stile-and-rail core or solid wood core) uses bonded wood blocks or lumber strips as the core material. Stave core provides the highest structural strength and screw-holding capacity of any flush door core. These doors weigh approximately 60-80 pounds for a standard 3070 door. Stave lumber core is specified for doors requiring heavy-duty hardware (such as continuous hinges), high-abuse resistance, or superior sound attenuation. Fire ratings up to 20 minutes are available with stave lumber core construction.

Core Types

A flush door has flat, smooth faces without raised or recessed panels. The door consists of a core material sandwiched between two face sheets, with edge banding (stiles) on the vertical edges and rails at the top and bottom. Flush doors are the most widely specified door type in commercial construction due to their versatility, range of available fire ratings, and compatibility with standard hardware preparations.

CDF Distributors supplies commercial flush doors through its partnership with Masonite Architectural, one of the largest wood door manufacturers in North America. CDF's ProBuilder configuration tool allows specifiers to select the core type, face material, fire rating, and hardware preparation for Masonite flush doors as part of a complete door assembly.

Overview of Commercial Flush Doors

A specification guide to commercial flush door core types, face materials, fire ratings, and application criteria for interior and exterior openings.

This guide answers: What are the construction types and applications for commercial flush doors?