Lead Structural Engineer • Published: August 2026 • 10 min read
NBC 105:2020 vs NBC 105:2025: Critical Code Shifts
For several years following the 2015 Gorkha earthquake, structural calculations in Nepal referenced the interim NBC 105:2020 draft. With the official gazetting of NBC 105:2025 by the Government of Nepal, municipalities such as Itahari Sub-Metropolitan, Dharan, Biratnagar, and Kathmandu have updated their permit vetting benchmarks.
Submitting engineering documentation citing outdated NBC 105:2020 or NBC 105:1994 can result in municipal approval delays or rejection during e-BPS scrutiny. Here is an engineer’s breakdown of what changed.
Summary of Major Code Differences
| Design Parameter | NBC 105:2020 (Interim) | NBC 105:2025 (Current Gazetted Standard) |
|---|---|---|
| Status & Legal Enforcement | Interim draft guidelines | Legally gazetted national building code |
| Seismic Hazard Map (Z) | Generalized regional contours | Finer municipality-specific probabilistic seismic hazard grid |
| Inter-Story Drift Limit | 0.025 $h_s$ (2.5% story height) | 0.020 $h_s$ (2.0% story height for standard occupancy) |
| Torsional Irregularity | Basic 1.2 drift ratio check | Mandatory 3D eccentric modal mass participation checks |
| Soil Stratification | Four broad soil classes | Stringent V_s30 and $N_60$ depth-weighted criteria |
Why This Matters to Building Owners
The tighter drift limit (2.0% vs 2.5%) under NBC 105:2025 significantly reduces non-structural damage (such as partition wall cracking, plumbing breakage, and facade shattering) during moderate earthquake tremors. For home owners and commercial developers, designing to NBC 105:2025 ensures superior building longevity, lower post-earthquake repair costs, and frictionless municipal approval.
Regulatory Citations:
- Nepal Gazette, Ministry of Urban Development (DUDBC) — NBC 105:2025
- DUDBC Electronic Building Permit System (e-BPS) Technical Vetting Guidelines
- Nepal Engineering Council (NEC) Code of Ethics & Practice Standards
Upgrade Outdated Structural Drawings
Ensure your pending building design is fully compliant with NBC 105:2025 before municipal submission.
Request Structural Vetting