According to Indian modular brick practice, what is the standard actual size of a modular brick (excluding mortar thickness)? (Note: Distinguish between actual and nominal dimensions.)

Introduction:
Masonry measurements often distinguish between actual unit size and nominal (including mortar). This question checks recall of the standard actual size of a modular brick used in India.

Given Data / Assumptions:

• Modular brick systems in India specify both actual and nominal sizes.
• Mortar thickness is typically around 10 mm, leading to a larger nominal size.
• The question explicitly asks for actual size.

Concept / Approach:
Actual size is the physical brick dimension measured without mortar; nominal size adds the intended mortar joint to simplify layout modularity on site.

Step-by-Step Solution:

Verification / Alternative check:
Codes and handbooks list 19 × 9 × 9 cm as actual, with 10 mm mortar joints giving nominal 20 × 10 × 10 cm module for coursing and openings.

Why Other Options Are Wrong:

• 10 × 10 × 9 cm: not a recognized standard module.
• 22.5 × 10 × 8.5 cm and 22.5 × 8.0 × 9 cm: resemble non-modular or historical sizes; not the Indian modular actual size.

Common Pitfalls:
Confusing actual with nominal; ignoring mortar thickness when setting out openings and lintels; mixing regional sizes.

Final Answer:
19 × 9 × 9 cm (actual size)