Unreinforced masonry homes carry elevated seismic collapse risk

Description

Older homes built of unreinforced brick or concrete block (URM) are more vulnerable to earthquake collapse than wood-frame or reinforced-masonry equivalents because of their mass and lack of internal reinforcement. URM construction is no longer permitted in seismic zones under current ICC codes; existing URM homes should be evaluated by a qualified design professional and retrofitted where feasible.

Why this exists

URM is one of the most consistently-documented vulnerable building types in seismic post-event surveys. FEMA P-2325 names it explicitly: 'an older unreinforced masonry homes... are more vulnerable to collapse in an earthquake because of their mass and lack of adequate reinforcement.'

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.

Plan symbols this applies to

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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