Timber standards (IS 399:1963) – reference moisture content for specifying weight According to IS 399:1963, the weight of timber is specified at which reference moisture content?

Introduction / Context:
The moisture content of timber significantly affects its weight, strength, and dimensional stability. Standards specify a reference moisture content to ensure comparable measurements and fair trade. This question checks the Indian Standard convention used when specifying the weight of timber for engineering and commercial purposes.

Given Data / Assumptions:

• Indian Standard IS 399:1963 covers timber characteristics and related data.
• Weight (density) varies strongly with moisture; a standard reference is required.
• We choose the commonly adopted reference for seasoned timber specifications.

Concept / Approach:

Seasoned timber used in buildings is often referenced at approximately equilibrium moisture content for many service environments. IS practices and engineering texts commonly specify properties (including weight) at 12% moisture content, a representative target for seasoned wood in moderate climates, permitting consistent comparison across species and batches.

Step-by-Step Solution:

Verification / Alternative check:

Handbooks summarizing IS practices align mechanical and physical timber properties around 12% MC, reinforcing its status as the reference condition.

Why Other Options Are Wrong:

8% / 10%: Too low for standard building service conditions in many Indian climates.

14%: Used in some contexts but not the canonical reference for weight in IS 399:1963.

Common Pitfalls:

Confusing air-dry equilibrium for specific climates with the standard reference; assuming “kiln-dry” values apply universally.

Final Answer:

12% moisture content