Architrave profiles: pencil round, half-splay, lambs tongue, colonial and shadowline

TL;DR

Architrave is the trim that frames door and window openings, hiding the gap between the frame and the wall lining. Profile choice is a styling call, not a structural one: match the architrave family to the skirting profile, scale the width to the opening (42-67 mm for contemporary, 90-185 mm for heritage), and pick the material to suit the location (FJ pine in wet zones, MR MDF for painted finish elsewhere, hardwood for stained or natural finish). The two specification decisions that drive cost and rework: profile width (wider widths cost more and need cleaner stud setouts) and the corner detail (mitred 45-degree joints are default; a square-set or shadowline reveal is a separate trade-off that affects sequence, not material choice). Intrim, Porta, and Woodhouse supply the bulk of the Australian residential market; most profiles are available in matching skirting and architrave widths.

What it is

Architrave is the moulded or flat trim board fixed around the perimeter of door and window openings. Two jobs:

Cover the construction gap: the gap between the jamb or window frame and the wall lining, typically 3 to 10 mm depending on how the chippy set out the frame
Frame the opening visually: provide a finished line that completes the architectural style of the room

The profile is the cross-section shape of the architrave board. The same profile families are offered as matching skirting (taller, at the floor) and architrave (narrower, around openings), scaled down for the narrower width.

Also known as: architrave moulding, door trim, casing (US).

Category: Internal trim.

Sizing rules of thumb

Element	Typical residential range
Architrave width	42 to 67 mm contemporary, 90 mm and above for heritage and traditional
Architrave thickness	12 mm (slim contemporary), 18 mm (standard residential), 25 mm (hardwood, heritage)
Reveal (the visible flat between the architrave outer edge and the door jamb)	3 to 8 mm; defines whether the door reveals as a shadow line or a flush detail
Architrave-to-skirting relationship	Architrave outer face typically lines up with the skirting outer face, or proud by 2-3 mm. Architrave inside the skirting face is a defect.
Mitre angle	45 degrees standard at top corners; 22.5 degrees on splayed openings

The width call is largely a styling decision. The thickness call is more practical: 18 mm is the residential default because it pairs with standard 90 mm or 138 mm jamb depths and accepts a 38 mm or 50 mm bullet head nail without splitting.

Profile types

The same profile names used in skirting profiles apply to architrave, scaled down. The most common profiles in Australian residential work:

Pencil round

The simplest decorative edge: flat-back board with a small rounded top edge (approximately 3 mm radius). Suits contemporary, coastal Scandinavian, and Art Deco interiors. Volume builders’ default for new estate housing.

Intrim and Porta both offer pencil round in FJ Pine, MR MDF, and American Oak. Common architrave widths: 42, 50, 60, 67 mm (verified 2026-05-13, Intrim Mouldings architrave range).

Half-splay

A flat-back board with the top face angled at 45 degrees from back to front. No curves; a sharp clean chamfer. The default modern minimalist trim. Pairs with shaker-style cabinet doors.

Widths typically 42, 66, 90, 115 mm. The narrower widths read cleanly around contemporary internal doors; 90 mm and above start to feel heavy unless the ceiling height supports it.

Lambs tongue (NSW colonial)

The “S-bend” ogee profile, curving concave-then-convex from the architrave outer edge into a V-joint at the inner edge. Traditional NSW colonial detail. Widely available in FJ Pine and MR MDF.

Typical widths 42 to 90 mm in architrave; the larger sizes (115, 185 mm) are matched-skirting widths, less commonly used as architrave.

Colonial (VIC colonial and Federation)

A multi-stepped profile with two or three distinct bands separated by small flat shadow lines. The Federation, Victorian, and Edwardian eras all used variants. Sometimes called Federation architrave; some suppliers distinguish by step count or curve radius.

Widths 67 to 135 mm typical; heritage renovations may go to 185 mm to match original room scale.

Ovolo (quarter-round and Roman)

A single convex curve on the architrave face. A quieter heritage option that suits Edwardian and Californian Bungalow homes. Often used where a colonial profile would feel too ornate.

Widths 67 to 115 mm common.

Square-set with shadowline reveal

Not a profile of the architrave itself; an alternative to architrave. The wall lining returns into the door frame via a shadow line or a square-set bead, dispensing with the architrave entirely. The detail requires the wall sheeter and the door frame setter to coordinate before the linings go on; it cannot be added retrospectively without re-sheeting.

Square-set gives a flush plaster-to-jamb meeting; shadowline gives a controlled 5 to 10 mm recess. Both are higher-cost, higher-aesthetic details suited to contemporary architectural work. The architrave is omitted but the detail moves into the plasterer’s scope and adds days to programme.

Materials

Material	Where to use	Cost (2026 indicative, per linear metre, ex-GST)	Watch for
FJ pine (finger-jointed pine, primed)	Wet areas, laundries, high-humidity zones; anywhere paint will cover the finger joints	$5 to $12 per LM (width-dependent)	Visible finger joints under thin paint; needs 2-coat undercoat
MR MDF (moisture-resistant medium-density fibreboard, primed)	All internal dry-zone trim; the volume default for painted finish	$4 to $10 per LM	Absorbs water at any cut or unsealed end; do not use in wet areas
Standard MDF (primed, non-MR)	Bedrooms and living-area trim in low-humidity locations	$3 to $8 per LM	Swells if it ever sees water; some builders refuse to spec it in AU climates
American Oak (clear or stain grade)	Stained or natural-finish work; high-end joinery	$25 to $60 per LM	Cost; movement with humidity in unsealed timber
Hardwood (Tasmanian Oak, Vic Ash, Spotted Gum)	Heritage restoration to match existing trim; commissioned work	$30 to $80+ per LM	Long lead times; expect to mill or order custom
PVC / cellular composite	Wet rooms, pool surrounds, exterior soffits	$8 to $20 per LM	Limited profile range; some products do not paint well

MR MDF and FJ Pine dominate the residential market by volume. The pine premium over MDF is roughly 20 to 40% but reads better at the wet zone boundaries and resists denting from second-fix knocks.

Suppliers (Australian residential market)

The same three suppliers dominate skirting and architrave; profiles in their architrave catalogue match the skirting profiles, scaled to width:

Intrim Mouldings: broadest catalogue, all material classes (FJ Pine, MR MDF, American Oak) in matched skirting and architrave widths. NSW-based but national delivery.
Porta: strong on contemporary profiles (pencil round, half-splay) and the Meranti timber range; common in eastern-states volume builders.
Woodhouse: heritage and traditional focus; FJ pine and primed MDF in colonial and Federation profiles. Strong in Victoria.

Brand selection is mostly a function of who the local timber merchant stocks. For a specifier-led job, Intrim’s profile catalogue is the broadest single reference.

Installation notes (cross-reference to the install guide)

Profile choice has knock-on effects for the second-fix chippy:

Mitre joints: 45-degree cuts at the top corners of all openings is default. The mitre must close cleanly on both faces; gaps over 1 mm are a defect under workmanship standards.
Square-cut head, mitred jambs: some traditional profiles (Federation, Colonial) sit better with a square-cut top architrave with mitred jambs returning into it. Specify on the SoW.
Glue-jointing at mitres: the mitre is glued (PVA or MS polymer) before nailing. Glue creep under paint is one of the most visible defects six months after handover; wipe clean before the coat goes on.
Nail spec: 38 mm or 50 mm bullet head nails through the architrave into the jamb and stud. Brad-nailed or hand-nailed; either works. Punch and fill before the painter is on site.

The matching install procedure lives in practical/skirting-and-architrave-install.

Common defects to look for

Mitre gaps: a 1 to 2 mm gap shows through paint. Cause is usually an out-of-square door frame or careless cutting. Close gaps with paintable caulk only as a last resort; recut the mitre where the gap exceeds 1 mm.
Reveal inconsistency: the visible flat between the architrave inner edge and the door jamb varies opening to opening. Spec the reveal width (typically 5 mm) and confirm at first opening before fitting the rest of the floor.
Architrave behind skirting: a defect almost always caused by skirting installed after architrave with the wrong sequence. Fit architrave first, skirting butts up to it.
MR MDF swelling at wet zones: a year on, the MDF blooms at the laundry, bathroom, and ensuite. Use FJ pine architrave in any wet zone.
Visible MDF finger joints showing through paint: low-cost MDF flexes through finger joints under thin paint. Three coats minimum on FJ pine; 2-coat undercoat + topcoat on MDF if budget allows.
Architrave too narrow for ceiling height: 42 mm architrave around 2700 mm-high doors reads thin. Match the architrave width to opening size and ceiling scale.

Standards and references

Intrim Mouldings, Skirting and architrave product catalogue. https://intrimmouldings.com.au/skirting-boards-and-architraves/architraves/ (verified 2026-05-13).
Australian Building Codes Board, NCC 2022 ABCB Housing Provisions (no specific DTS for architrave trim; falls under workmanship and second-fix standard practice). https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions (verified 2026-05-13).
Housing Industry Association, HIA Guide to Materials and Workmanship (paywalled; workmanship tolerances for second-fix trim including mitre tightness and reveal consistency). https://hia.com.au (verified 2026-05-13).