Running a second-fix (fix-out) carpentry quote or ordering internal timber mouldings requires far more than just measuring wall perimeters. To avoid paying for excessive offcuts or running short mid-job, you need to subtract door jamb openings from your skirting run, calculate double-sided architrave sets for passage doors, account for 45° scarf joint overlaps, and convert net requirements into standard Australian 5.4-metre trade lengths sold by suppliers like Porta, Intrim, Hume, and Bunnings Trade.
How to Calculate Skirting Board & Architrave Lineal Metres
A clean material take-off breaks down internal timber mouldings into two distinct components: base skirting boards along the bottom of the wall, and vertical/horizontal architrave frames enclosing door and window openings.
1. Measuring Gross Wall Perimeter
Measure the length of every individual wall in the room along the floor line. For a standard rectangular room measuring 5.0m × 4.0m, the gross perimeter is (5.0 + 4.0) × 2 = 18.0 metres.
2. Subtracting Doorway Openings
Skirting boards terminate at the door architrave block or casing; they do not cross doorway openings. For every doorway, deduct the opening width plus the architrave reveal:
- Standard Single Internal Door (820mm door leaf): Deduct 0.87 metres (870mm) per opening to account for the clear door jamb and 67mm architrave casing.
- Standard Wide / Double Door (1640mm opening): Deduct 1.70 metres (1700mm) per opening.
- Large Sliding / Bi-Fold Doors (2400mm+ opening): Deduct the full rough opening width plus 100mm.
3. Calculating Door Architrave Sets
Architraves frame the perimeter of the door jamb. Each side of an internal doorway requires three pieces of moulding: two vertical legs and one horizontal head.
Single Door Architrave (1 Side) = (2 × 2.1m Legs) + (1 × 1.0m Head) = 5.2 Lineal Metres
Because standard internal passage doors (e.g. between bedrooms and hallways) require architraves on both sides of the wall, a single doorway consumes 10.4 lineal metres of moulding. Wardrobes and external doors generally require architrave on the internal side only (5.2 Lm).
4. Calculating Window Architraves
Unless your window reveals are finished with plasterboard square-set bead, windows require a 4-sided architrave frame (2 vertical legs + 1 head + 1 bottom apron/sill piece).
Window Architrave (Lm) = (2 × Window Height) + (2 × Window Width) + 0.4m (Corner Overlaps)
For example, a standard 1.2m × 1.2m domestic window requires approximately (2 × 1.2) + (2 × 1.2) + 0.4 = 5.2 lineal metres of architrave.
5. Ordering in Standard 5.4m Stock Lengths (+10% Waste)
Timber merchants supply primed pine and MR MDF mouldings in 5.4-metre lengths (as well as 4.2m and 2.7m lengths). Always add a 10% wastage allowance to your gross lineal metres to cover 45° angle cuts, corner scribes, and scarf joint offcuts before dividing by 5.4 to determine how many whole lengths to order.
Skirting Board Height & Profile Guide for Australian Ceilings
Choosing the correct skirting profile and height depends on the ceiling height and architectural era of the home. Undersized skirting boards in tall rooms look flimsy, while oversized mouldings in low-ceiling rooms make spaces feel compressed.
| Ceiling Height | Recommended Skirting Height | Matching Architrave Width | Typical Australian Home Style |
|---|---|---|---|
| 2.4 m (Standard Ceiling) | 67 mm to 90 mm | 42 mm or 67 mm | Modern project homes, apartments, post-war brick veneer, budget renovations. |
| 2.7 m (9ft High Ceiling) | 90 mm to 140 mm | 67 mm or 90 mm | Contemporary custom homes, modern Hamptons, mid-century renovations. |
| 3.0 m to 3.6 m (High Ceiling) | 140 mm to 185 mm | 90 mm or 115 mm | Victorian terraces, Federation homes, Queenslanders, classic period restorations. |
| 3.6 m+ (Grand Period) | 185 mm to 230 mm+ | 115 mm to 140 mm | Heritage estates, grand Victorian homesteads with high decorative cornices. |
Popular Australian Timber Moulding Profiles
- Single Bevel / Pencil Round: Sleek 45° top chamfer. The number one choice for modern minimalist and contemporary Australian project homes because it doesn't collect dust and wipes down effortlessly.
- Lambs Tongue: Classic S-curved decorative profile with a traditional heritage look. Ideal for Federation, colonial, and Victorian cottage renovations.
- Half Splayed: Subtle curved taper transitioning into a flat face. A timeless versatile profile found across thousands of 1980s–2000s Australian homes.
- Stepped / Shadowline: Square profile with one or two recessed horizontal steps. Very popular in architecturally designed minimalist and industrial interiors.
- Colonial / Regency: Deep intricate routing suited for period restorations, dado wall panelling, and grand entrance halls.
Material Comparison: Primed Finger-Jointed Pine vs MR MDF vs Hardwood Trims
Selecting the right substrate ensures clean cuts, easy nailing, and long-term durability against vacuum cleaner knocks and mop water:
1. Primed Finger-Jointed Pine (FJ Pine)
Manufactured from solid plantation Radiata Pine pieces finger-jointed together to eliminate natural knots, then coated with an ultra-smooth factory acrylic primer.
- Pros: Flexible enough to bend along slightly wavy or bowed stud walls; holds 15-gauge finish nails securely; moisture-resistant compared to standard chipboard; easy to hand-plane and scribe with a coping saw.
- Best For: Renovation sites with imperfect plasterboard, timber stud framing, and high-traffic family hallways.
2. Moisture Resistant (MR) Green Core MDF
Engineered from fine wood fibres bonded with high-density moisture-repellent synthetic resins.
- Pros: Completely knot-free, dead straight, and provides a glass-smooth spray or brush finish without grain raise; generally 20% to 30% cheaper than solid timber.
- Cons: Brittle on sharp mitre edges; produces very fine dust when cut requiring P2 respirator masks; less flexible on wavy walls.
- Best For: Brand new straight stud framing, modern square-set homes, and budget-conscious second-fix fit-outs.
3. Solid Hardwoods (Tasmanian Oak / Victorian Ash / Merbau)
Kiln-dried Australian native hardwoods machined into decorative profiles for clear polyurethane or oil finishes.
- Pros: High natural density and surface hardness that resists dents and scratches; rich natural timber grain that matches hardwood or engineered timber flooring.
- Cons: Requires pre-drilling near board ends to prevent splitting; significantly higher material cost ($15–$30+/Lm).
- Best For: High-end architectural homes and matching stained timber floorboards.
If you are installing timber or hybrid flooring prior to fixing skirting, calculate your flooring packs and underlay with our Flooring Calculator.
Cutting & Jointing Guide: Internal Scribing vs External 45° Mitres vs Scarf Joints
How you join skirting boards and architraves separates a rough amateur finish from professional second-fix carpentry:
1. Why You Should Never 45° Mitre Internal Corners (Always Scribe)
In Australian residential construction, room corners are rarely perfectly square (90.0°). If you cut standard 45° mitres on inside corners, seasonal timber frame expansion and timber shrinkage will cause the heel or toe of the mitre to open up, leaving an ugly gaping seam.
The Trade Solution — Scribed (Coped) Joint:
- Run the first skirting board square (butt joint) right into the plasterboard corner.
- Cut the second board at a 45° inside mitre on your drop saw. This highlights the exact profile outline on the front timber face.
- Using a hand coping saw (or angle grinder with a sanding flap disc), cut back along that pencil-thin profile line with a slight 5° back-bevel.
- Slide the scribed profile over the face of the first board. It interlocks seamlessly and remains invisible even if the wall frame moves or shrinks.
2. External Corners (45° External Mitres)
Outside corners on chimney breasts, nib walls, or hallway returns must be cut on a 45° external mitre. Measure corner angles with a digital angle finder—if the corner is 92°, cut each board at 46.0°. Check your saw turntable angles using our Mitre Angle Calculator. Always apply PVA wood glue or instant cyanoacrylate (mitre glue) to external joins and pin the tip with 18-gauge headless brads.
3. Scarf Joints on Long Wall Runs (Over 5.4m)
When a wall length exceeds your 5.4m timber moulding, join two pieces using a 45° scarf joint directly over a timber wall stud. Never butt two boards square on a flat wall—a straight butt joint will eventually crack along the paint line. Overlapping the boards at 45° allows the joint to be nailed into the stud and sanded dead flat.
4. Architrave Jamb Reveals (5mm to 6mm Setback)
Never install door architraves flush with the inside face of the door jamb. Always leave a consistent 5mm to 6mm reveal (margin) on the door jamb edge. This provides clearance for door hinges, prevents latch strike plates from fouling the moulding, and creates a neat shadowline.
Nailing Patterns, Fasteners & Caulking Rules
Skirting boards must be fastened directly into the structural timber frame behind the plasterboard, not merely into the 10mm Gyprock sheet:
- Fastening to Bottom Plate & Wall Studs: Drive finish nails into the timber bottom plate (angled slightly downward 15mm off the floor) and double-nail into every vertical wall stud (spaced at 450mm or 600mm centres). Locate studs using a magnetic stud finder or our Wall Framing Calculator layout.
- Nail Gun Selection: Use a 15-gauge or 16-gauge angled finish nailer with 50mm DA brad nails for securing skirting through 10mm plasterboard into framing. Use a lighter 18-gauge C1 brad nailer (32mm–38mm pins) for pinning delicate architrave mitres and quad trims.
- Construction Adhesive: On masonry or brick veneer walls where timber studs are absent, apply generous daubs of polyurethane construction adhesive (HB Fuller Max Bond or SikaBond) to the back of the board and secure with masonry pins or temporary prop sticks until cured.
- Flexible Acrylic Gap Filler: Run a continuous fine bead of paintable flexible acrylic caulk (Selleys No More Gaps) along the top joint where the skirting meets the plaster wall. This hides minor wall undulations and absorbs seasonal timber movement without cracking.
Real-World Worked Example: Master Bedroom & Ensuite Take-Off
Here is an accurate second-fix material order for a 4.5m × 4.0m Master Bedroom with 2 standard internal doors (Hallway entry & Ensuite) and 1 window (1.8m wide × 1.2m high):
- Calculate Gross Room Perimeter:
(4.5m + 4.0m) × 2 = 17.0 metres. - Deduct Doorway Openings: 2 single doors × 0.87m deduction = -1.74 metres.
- Net Skirting Required: 17.0m - 1.74m = 15.26 lineal metres.
- Add 10% Wastage for Skirting: 15.26m × 1.10 = 16.79 Lm → 4 lengths of 5.4m (21.6 Lm ordered).
- Calculate Door Architrave: 2 doors × (2 sides) × 5.2 Lm per side = 20.8 lineal metres.
- Calculate Window Architrave: (2 × 1.8m width) + (2 × 1.2m height) + 0.4m overlaps = 6.4 lineal metres.
- Total Net Architrave: 20.8m + 6.4m = 27.2 lineal metres.
- Add 10% Wastage for Architrave: 27.2m × 1.10 = 29.92 Lm → 6 lengths of 5.4m (32.4 Lm ordered).
- Consumables Required: 1 box of 50mm 15-gauge DA finish brads (~500 nails) + 2 tubes of Selleys No More Gaps.
- Total Estimated Cost: 4 lengths 90mm skirting ($97.20) + 6 lengths 67mm architrave ($123.12) + fixings/caulk ($34.00) = $254.32 AUD (incl. GST).
Trade Tips for Flooring Expansion, Uneven Floors & Painting Prep
Follow these pro second-fix chippy practices for a flawless finish:
- Floating Floor Expansion Clearance: When installing laminate, hybrid, or engineered timber floating floors, always leave a 10mm to 12mm expansion gap between the flooring edge and the wall plasterboard. Install the skirting board over the top of the flooring to conceal this expansion perimeter. Never pin or nail the skirting down into the floorboards—nail exclusively into the wall studs so the floor can expand freely beneath.
- Fitting Over Existing Skirting (Scotia / Quad): If you are laying new floating floors without removing existing skirting boards, install matching 19mm Scotia or Quad moulding pinned horizontally into the base of the skirting to cover the floor expansion gap.
- Scribing to Uneven Floors: If an old timber floor or tiled bathroom has a slight sag or hump, place your skirting board against the wall, set a carpenter's pencil on a small timber block running along the floor, and scribe the floor contour onto the bottom edge of the skirting board. Plane down to the line with an electric planer for a seamless floor contact.
- Pre-Priming & First Coat: Always apply your first coat of satin or semi-gloss enamel paint onto your timber mouldings while they are resting on sawhorses outside before installation. It is 10 times faster to paint mouldings on horses than cutting in on your knees next to brand new carpet. Once nailed and gap-filled, apply only a final light finish coat.