Understand the relationship between door leaf sizes and clear width for accessible doors.

In architectural documentation, one of the most frequent technical errors occurs when a graduate confuses the size of a door leaf with the compliant clear opening. While it is tempting to simply drop a standard 870mm or 920mm door into a floor plan, these dimensions rarely represent the actual width available for a person to pass through.

Failing to account for the physical reality of frames, stops, and hardware can lead to significant accessibility non-compliance and costly site variations. To document with precision, you must understand the relationship between standard manufacturing sizes and the functional clear opening width.

1. Understanding Standard Australian Door Sizes

Before performing any calculations, you must be familiar with the standard door leaf widths available in the Australian market. Designing around these sizes prevents unnecessary custom fabrication costs.

Standard residential and commercial timber door leaves typically come in the following widths:

• Common Standards: 720mm, 770mm, 820mm, 870mm, and 920mm

• Large Standards: 970mm and 1020mm

• Custom: Anything > 1020mm

2. Defining the "Clear Opening width" vs. the "Leaf width"

The Door Leaf width refers to the physical dimension of the door panel itself. In contrast, the Clear Opening Width is the unobstructed space available when the door is fully open.

For a path of travel to be considered accessible under AS 1428.1, a minimum clear opening width of 850mm is required.

3. Calculating the Hinged Door Clearance

For a standard hinged (swing) door, the clear opening width is measured from the face of the door stop to the face of the door leaf when the door is open at 90°.

The formula for a hinged door leaf is as follows:

Minimum Leaf Size = Required Clear Width + Door Stop thickness + Hinge Gap + Leaf Thickness - (2 x 3mm clearance each side)

Step-by-Step Verification:

1. Start with your required 850mm clear width.

2. Add the thickness of the door stop and hinge gap. 

   1. Timber frames: 11–12 mm 

   2. Steel frames: 15mm (non-fire rated doors) & 25mm (fire rated doors)

   3. Hinge gap: ~5mm

3. Add the thickness of the door leaf itself:

   1. Standard door thickness: 35 mm & 40 mm

   2. Fire door thickness: 

      1. Maxi doors (45 to 48 mm) provide an FRL up to 2 hrs for double doors and 3 hrs for single doors.

      2. Mini doors (36 to 38 mm) provide an FRL of 1 hr for single doors

4. Subtract the 2 x 3mm gap on each side of the door leaf to fix the door into position in the frame.

5. Calculate the minimum leaf width using the formula above.

6. Choose a standard door leaf size that is larger than the minimum leaf size calculated.

4. Calculating the Sliding Door Clearance

Sliding doors (both cavity and surface-mounted) operate on a different logic. Per accessibility standards, a sliding door must not retract fully into the pocket; it requires a "hand-hold" clearance so the hardware remains accessible.

The formula for a sliding door leaf is as follows:

Minimum Leaf Size = Required Clear Width + (Stile Offset * 2) + Handle width

Step-by-Step Verification:

1. Start with your 850mm clear width.

2. Add a 60mm offset for the leading stile and a 60mm offset for the trailing stile (to ensure the handle is accessible from both sides).

3. Add the width of the handle. 

4. Calculate the minimum leaf width using the formula above.

5. Choose a standard door leaf size that is larger than the minimum leaf size calculated. 

Architecture is in the details. If you want to move beyond basic plans and start documenting like a Lead Architect, explore our comprehensive detailing modules at ArchiUpskill.

Disclaimer: This guide provides general oversight only. All project-specific documentation must be verified against AS 1428.1 and the National Construction Code (NCC) to ensure site-specific compliance. Professional advice should be sought for unique design conditions.