Interior Door Specifications for Contractors: STC, AWI, Rough Opening & Jamb Depth Guide

Quick Answer: Interior door specifications for contractors include STC ratings (28–45 for residential, 45+ for multifamily), AWI grade classifications (Economy, Custom, Premium), pre-hung rough opening sizes (width + 2.5 inches, height + 2 inches), and door jamb depths (4-9/16 inch for 2×4 walls, 6-9/16 inch for 2×6 walls). WholesaleDoorHub supplies spec-grade wholesale interior doors 35–55% below retail MSRP with no minimum order on in-stock items.

Interior Door Specifications Every Contractor Must Know

Ordering the wrong door specification is one of the most costly mistakes on a job site. A door ordered with the wrong STC rating, wrong AWI grade, or wrong jamb depth can delay a project by weeks and add significant cost. This guide covers every specification parameter contractors need to order correctly the first time.

STC Rating: Sound Transmission Class for Interior Doors

Sound Transmission Class (STC) measures how well a door blocks airborne sound. Higher numbers mean better sound isolation. For residential projects, the minimum acceptable STC rating for bedroom and bathroom doors is STC 28–33. For multifamily and commercial applications, STC 38–45 is the industry standard. Premium acoustic applications such as home theaters and recording studios require STC 45+.

Hollow core doors typically achieve STC 20–28. Solid core doors with MDF or particleboard cores achieve STC 28–38. Solid wood doors with acoustic seals can reach STC 38–45. When specifying doors for apartment buildings, confirm local building codes — many jurisdictions require a minimum STC 50 for party walls, which affects door selection for units sharing a wall.

AWI Grade Classifications: Economy vs. Custom vs. Premium

The Architectural Woodwork Institute (AWI) defines three grade levels for interior doors that determine material quality, tolerances, and finishing standards. Economy Grade uses lower-grade veneers and allows more variation in grain and color matching — appropriate for utility spaces, closets, and rental properties where aesthetics are secondary to function. Custom Grade is the most commonly specified grade for residential and light commercial construction, offering consistent grain matching and tighter tolerances. Premium Grade requires the highest quality veneers, book-matched panels, and the tightest manufacturing tolerances — specified for high-end residential, hospitality, and commercial interiors.

WholesaleDoorHub stocks Custom Grade as the default for all product lines, with Economy Grade available for high-volume rental property projects and Premium Grade available on special order.

Pre-Hung Door Rough Opening Calculations

The rough opening is the framed opening in the wall into which a pre-hung door unit is installed. Calculating the correct rough opening size is critical — too small and the door won't fit, too large and shimming becomes excessive and structurally compromised.

The standard formula: Rough Opening Width = Door Width + 2.5 inches. Rough Opening Height = Door Height + 2 inches. For a standard 32×80 door, the rough opening should be 34.5×82 inches. For a 36×80 door, the rough opening should be 38.5×82 inches.

Door Jamb Depth: 4-9/16 vs. 6-9/16 Inch

Door jamb depth must match the wall thickness at the installation location. Standard 2×4 stud walls with 0.5-inch drywall on each side measure 4.5 inches total — requiring a 4-9/16 inch jamb. Standard 2×6 stud walls with 0.5-inch drywall on each side measure 6.5 inches total — requiring a 6-9/16 inch jamb. Always measure the actual wall thickness at the installation point before ordering, as framing inconsistencies are common in older construction.

MDF vs. HDF Door Core Specifications

Medium Density Fiberboard (MDF) cores (density 600–800 kg/m³) are standard in most hollow core and economy solid core doors. They accept paint well, resist warping in stable environments, and are cost-effective for high-volume projects. High Density Fiberboard (HDF) cores (density 800–1,100 kg/m³) are used in premium solid core doors, offering better screw-holding strength, improved sound attenuation, and greater resistance to denting and impact.

Door Slab vs. Pre-Hung Unit: Which to Order

A door slab is the door panel only — no frame, no hinges, no hardware. A pre-hung unit includes the slab, frame, and hinges, ready to drop into a rough opening. For new construction and full gut renovations, pre-hung units save significant labor time. For replacement projects where the existing frame is in good condition and square, door slabs are more cost-effective. WholesaleDoorHub offers both formats across all 20 product categories.

Mortise and Tenon vs. Dowel Door Construction

Traditional mortise and tenon joinery uses interlocking rectangular cuts to connect door rails and stiles, creating a mechanically strong joint that resists racking forces. This construction method is found in solid wood doors and premium stile-and-rail doors. Dowel construction uses cylindrical wooden pegs — faster to manufacture and adequate for most residential applications, but less resistant to long-term racking. For commercial applications with heavy use, specify mortise and tenon construction for maximum durability.

Frequently Asked Questions

What STC rating do I need for apartment interior doors?

For interior doors within an apartment unit (bedroom, bathroom), STC 33–38 is typically sufficient. For doors opening to shared corridors, STC 38–45 is recommended. Check local building codes for specific minimum requirements.

What AWI grade should I specify for a rental property?

Economy Grade is appropriate for rental properties where durability and cost-efficiency are priorities. Custom Grade is recommended for mid-market rentals. WholesaleDoorHub's default stock is Custom Grade.

How do I calculate rough opening size for a pre-hung door?

Add 2.5 inches to the door width and 2 inches to the door height. For a 32×80 door, the rough opening is 34.5×82 inches.

What jamb depth do I need for a 2×6 wall?

A 2×6 wall with 0.5-inch drywall on each side measures 6.5 inches total. Order a 6-9/16 inch jamb depth.

Does WholesaleDoorHub offer doors with specific STC ratings?

Yes. Our solid core door line includes options rated STC 28, STC 33, STC 38, and STC 42. Fire-rated doors are available with STC ratings up to STC 45. Contact our wholesale team for specific STC requirements and we'll match you with the right product at contractor pricing.