Interior Doors Guide: Rough Openings, Hardware & IRC Code Compliance

The Eight Door Types Every Residential Plan Has to Pick From

Every interior door in a US home is one of eight types: pre-hung passage, slab passage, bifold, bypass / sliding closet, barn (wall-mounted sliding), pocket, French / double pair, or Dutch. Each carries its own rough-opening rule, hinge schedule, hardware kit, and casing demand. Mixing them up at the lumberyard is the most common reason a framing crew has to redo a header.

This guide is built on the standards the trade actually uses: ICC IRC 2021 (R311.2 egress, R302.5.1 garage-to-dwelling, R308.4 safety glazing, R310 EERO); the 2010 ADA Standards (§404 clear width, §309 operable parts); ANSI/BHMA A156.1 (butt hinges), A156.2 (bored locks), A156.13 (mortise locks), and A156.18 (finishes); NFPA 80 for the garage fire-rated door; and manufacturer technical data from Masonite, JELD-WEN, Reeb, L.E. Johnson, Eclisse, Cavity Sliders, Real Sliding Hardware, Schlage, Hager, and Stanley.

Standard Interior Door Dimensions

US residential doors are sold in nominal width × height × thickness. Heights default to 80″ (6′-8″) unless the plan specifies 84″ (7′-0″) or 96″ (8′-0″) for taller-ceiling rooms. Standard thickness is 1-3/8″ for hollow-core and most solid-core slabs, and 1-3/4″ for solid wood, French / double pairs, and the garage-to-dwelling fire-rated door.

Two width rules every plan should hit: the egress door per IRC R311.2 must produce a 32″ clear opening (which requires a 36″ nominal slab because thickness, hinge offset, and stop eat ~2-2-1/2″), and ADA-targeted projects per §404.2.3 want 32″ clear minimum, 36″ preferred. Other interior doors are not bound by R311.2 — IRC explicitly says “other doors shall not be required to comply.”

Rough Opening Rules (the part framers need)

Every door type has a different rough-opening formula. The pre-hung swing rule is universal across Masonite, JELD-WEN, Reeb, MMI, and Builders Surplus install guides; the pocket and barn rules vary by manufacturer and the calculator below uses the conservative value.

Pre-Hung vs. Slab: When to Use Which

A pre-hung door ships as a complete assembly — slab pre-mounted on three hinges inside a manufactured jamb (head + 2 sides) with the strike plate and hinge mortises already routed in. New construction and full door replacement default to pre-hung. A slab is the door panel only, used to replace a door in an existing jamb that is plumb and square.

Casing — the trim that frames the door on the room-facing side — is not included with a pre-hung kit. It's purchased and applied separately, and feeds into the trim & baseboard calculator. When ordering a slab, specify pre-bored (2-1/8″ face × 1″ edge at 2-3/8″ backset) and pre-mortised hinges if you want to skip field-routing.

Hollow Core vs. Solid Core: The Bedroom-Door Decision

The single biggest comfort upgrade in a remodel is swapping hollow-core doors for solid-core in bedrooms and bathrooms. Hollow-core is honeycomb cardboard between molded skins (~25–35 lb, STC 17–22). Solid-core is a particleboard or MDF slab between skins (~50–80 lb, STC 28–35) — about a 10-point STC bump, which is the difference between hearing every conversation in the next room and hearing none.

Hinges: How Many, What Size, What Bearing

ANSI/BHMA A156.1 sets hinge count by door height — and Hager, Stanley, and Bommer publish the same chart. The hinge-count rule is dead simple: 3 hinges for any 60″–90″ door (which covers the standard 80″ and 84″ slabs), 4 hinges for 96″ doors, plus one additional hinge for any door wider than 48″ or heavier than 200 lb.

Plain-bearing hinges (BHMA Grade 2 / 3) are fine for hollow-core and light solid-core slabs. Ball-bearing hinges are recommended for any door over ~50 lb and required for doors with closers — including the garage-to-dwelling fire-rated door. Standard residential placement is the 5/10 convention: top hinge 5″ from the top of the door, bottom hinge 10″ from the bottom, middle centered. Commercial-style heavier slabs use 7/11.

Locksets and Door Bores

Per ANSI A115.2 / BHMA A156.115, the universal residential bore is a 2-1/8″ face bore with a 1″ edge bore at a 2-3/8″ backset. (Heavy 1-3/4″ doors and commercial sometimes use a 2-3/4″ backset; most consumer locksets ship with an adjustable latch that does both.) Knob / lever centerline is 36″ above finished floor — comfortable for most adults and compliant with ADA §404.2.7's 34″–48″ window.

BHMA grade tracks cycle and impact resistance: Grade 3 (200,000-cycle test) is the residential default for passage and privacy; Grade 2 (400,000-cycle) is appropriate for premium residential and front-of-house openings; Grade 1 (800,000+ cycle) is commercial and rarely justified inside a home except for a high-traffic entry.

Bifold Closet Doors

A bifold pair is two panels joined by a continuous hinge that pivot from a top track. The pivot panel is fixed at the corner via a top pivot pin and an adjustable floor-bracket pin; the leading panel rides the track on a guide pin. Sold as a pair (2 panels) for openings up to 36″, or as a double pair (4 panels) for 48″–72″. Standard heights are 80″ and 96″.

Track is cut to nominal RO width and fastens flush to each end-jamb bracket. A standard kit (Johnson 1700, National 6970, Acme bifold) includes the track, top + bottom pivot brackets, the guide pin, screws, and a center alignment plate for double pairs. Knobs are typically purchased separately — 1 per pair, mounted on the leading panel.

Bypass Sliding Closet Doors

Two parallel tracks (front + rear) carry top-hung rollers, with a floor guide centered in the opening. Each door has 2 rollers — one at each top corner. The track length equals the opening width, and each door is sized at (opening / 2) + 1/2″ overlap so the meeting edges close the light gap when the doors are pulled together.

A bypass kit (Johnson 138, Stanley 2800, Prime-Line N 6517) includes the parallel tracks, 4 hangers, and a floor guide. Pulls are flush finger pulls mortised into the door face — typically 1 per door, so 2 per opening for the standard 2-door bypass.

Barn (Wall-Mounted Sliding) Doors

Barn doors mount to the wall on a surface track and do not change the rough opening — but they require a track at least 2× the slab width, which means the wall to the side of the opening must accommodate the full slid-open length plus the track.

For privacy coverage with no light gap on either side, size the slab wider than the opening:

Mount the track into solid blocking — either lag into wall studs at 16″ o.c. or, much better, into a continuous 1×4 or 1×6 backer board secured to studs along the entire track length. Pre-drilled track holes rarely line up with random stud spacing, so the continuous backer is the real-world answer. Standard residential hardware kits are rated 200 lb per pair of hangers (sufficient for any wood slab up to 1-3/4″ × 36″ × 84″); heavy-duty kits go to 400 lb for glass barn doors and oversized slabs.

Pocket Doors

Pocket doors retract into the wall cavity, which is the right answer when wall space is too tight for a swing — primary baths, ensuites, narrow halls, butler's pantries. The rough-opening rule is the headline number: for a single pocket per L.E. Johnson 1500, plan RO width = (2 × door width) + 1″ and RO height = door height + 4-1/2″. That means a 30″ door needs a 61″ rough opening.

Major frame brands and their capacities:

For privacy, mortise an edge pull with a thumbturn (Johnson 1535, Emtek 2103) into the leading edge of the slab; the thumbturn engages a pin into the strike jamb, with an outside coin slot for emergency entry. A passage pocket needs only an edge pull plus an inside flush pull — no thumbturn.

French and Double Doors

A double door is a pair of slabs that meet at center; French just means the same pair has glass lites. The hardware schedule is the same either way: 6 hinges (3 per leaf), an active lockset on the daily-use leaf, a dummy handle on the inactive leaf, and a pair of flush bolts top + bottom that hold the inactive leaf closed. An astragal — a vertical strip on the inactive leaf's meeting edge — overlaps the active leaf and closes the gap.

Per IRC R308.4, glass in doors and within a 24″ arc of door edges below 60″ AFF must be safety-glazed (tempered or laminated). The interior doors calculator's “has glass” toggle flags any glazed slab that doesn't carry the safety-glazing spec.

Dutch Doors

A Dutch door is a single door split horizontally into two leaves, each independently hinged. A Dutch door bolt (quadrant) locks the two leaves together so the assembly behaves as a single door. The most common residential split is roughly 2/5 top to 3/5 bottom — a 32″–34″ top leaf opens at adult chest height for service into a kitchen or pet containment in a mudroom or nursery. The hardware: 4 hinges (a pair per leaf), the Dutch bolt, a passage or privacy latch on the bottom leaf, an optional astragal between leaves, and an optional 7″–12″ shelf mortised onto the top edge of the bottom leaf.

Code: The Three Rules That Actually Matter

Most interior doors in a single-family home are not code-driven — IRC R311.2 explicitly says non-egress doors don't have to comply with the egress dimensions. Three rules are load-bearing:

The interior doors calculator emits explicit warnings when any door schedule violates these three rules — and refuses to validate a layout that puts a door from the garage into a bedroom.

Casing: How Many Linear Feet Per Door

Door casing is calculated separately and feeds into the trim calculator. The formula for a fully-cased opening, both sides, with 10% waste:

A typical 14-door, 3-bedroom / 2-bath home runs about 480 LF of casing — pass that directly into the trim & baseboard calculator to convert to sticks of 16′ stock plus fastener counts.

Worked Example: 3-Bedroom, 2-Bath House

15-door inventory for a typical 3 BR / 2 BA single-family home — the kind of list you'd hand to the lumberyard. The interior doors calculator's “Load 3 BR / 2 BA preset” button builds something close to this.

Aggregated bill of materials:

• 11 pre-hung passage units (10 hollow / solid core 1-3/8″ + 1 fire-rated 1-3/4″)
• 3 bifold pairs (single)
• 1 bypass kit (2-door, 72″)
• 1 pocket frame kit (28″, std-duty Johnson 1500 or equivalent)
• 33 hinges 3-1/2″ + 3 ball-bearing hinges 4″ (the fire-rated garage door)
• 6 passage locksets (F75) + 4 privacy locksets (F76) + 1 pocket privacy + 1 keyed entry (F81/F82)
• 3 bifold knobs + 2 bypass finger pulls
• 11 door stops (baseboard or hinge-pin)
• ~482 LF of 2-1/4″ colonial casing

That casing demand drops straight into the trim calculator; the wall openings drop into the drywall calculator as deductions; and the painted surfaces feed the interior paint calculator. That's the room-composer logic in action — one set of inputs, multiple coordinated trades.

Sources: ICC IRC 2021 (R311.2, R302.5.1, R308.4, R310, R311.6); 2010 ADA Standards (§404, §309); ANSI/BHMA A156.1 / A156.2 / A156.13 / A156.18 / A156.115; NFPA 80; manufacturer technical data from Masonite, JELD-WEN, Reeb, MMI Door, Builders Surplus, L.E. Johnson, Eclisse, Cavity Sliders, Real Sliding Hardware, Schlage, Kwikset, Hager, Stanley, and Bommer; Steel Door Institute SDI 111; Architectural Woodwork Institute (AWI) and WDMA construction standards.