Substantial damage threshold (50% of pre-disaster value) triggers full flood-code compliance on repair
FEMA P-2325 §Flood Hazard ProvisionsDescription
Homes in a Special Flood Hazard Area that have sustained damage equal to or greater than 50% of their pre-disaster market value are considered 'substantially damaged' and must be brought into full compliance with current flood provisions of the IRC when repaired — including elevation to BFE.
Why this exists
The substantial-damage rule is the primary mechanism by which existing nonconforming homes are converted to flood-resistant construction over time. Designers should plan with this trigger in mind for any home that has been or could be damaged near the 50% threshold.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
damageRatio | max | 50 | % of pre-disaster value | Damage at or above this threshold triggers full flood-code compliance |
Categories
Source
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Continuous load path from roof to foundation · HUD RSDG §2.4
- Residential structural reliability targets 1-in-100 to 1-in-1000 annual probability of failure · HUD RSDG §2.5
- Residential floor live load: 40 psf minimum (30 psf sleeping rooms) · HUD RSDG §3.4
- Wind load design uses ASCE 7 basic wind speed for the locality · HUD RSDG §3.6
- Ground snow load for Virginia: 25 psf eastern, up to 40 psf western mountains · HUD RSDG §3.7
Last reviewed 2026-05-11.