FEMA Building and Contents Debris Estimate

ScopeA debris estimate for a street of destroyed houses, a mobile home park, or a flooded neighborhood is built one structure at a time from FEMA's field formulas. A destroyed single-family house is its length times width times stories times 0.20 cubic yards per square foot, times a vegetative cover multiplier for the trees and shrubs that come down with it -- a single-story 40 by 50 ft house under medium canopy is 520 cubic yards, matching FEMA's table. The formula for a two-story house has a trap the field guide spells out: the vegetation belongs to the lot, not to each floor, so the multiplier applies to the first story's debris only. A two-story 30 by 40 ft house under medium canopy is 480 cubic yards of house plus 72 of vegetation, 552 in all; multiplying the whole house by 1.3 gives 624, 13% high, and over a neighborhood that becomes a contract for debris that does not exist. Mobile homes use FEMA's fixed figures (290 cubic yards single-wide, 415 double-wide) because they have little air space. A flooded house still standing produces only its ruined personal property, 25 to 30 cubic yards on a slab and 45 to 50 with a basement, so twelve flooded homes with basements put 540 to 600 cubic yards on the curb. Other buildings use length times width times height times 0.33 for air space, over 27: a 100 by 60 ft outbuilding 20 ft high is about 1,467 cubic yards, 733 tons at 2 cubic yards per ton. It does not replace load tickets, handle hazardous materials, asbestos, white goods, or electronics that must be segregated, or cover partial damage beyond flooded contents. FEMA Public Assistance and the applicant's debris management plan govern.

Formula or tablesingle-family house = L x W x S x 0.20 + L x W x 0.20 x (VCM - 1) cy, the VCM (none 1.0, light 1.1, medium 1.3, heavy 1.5) applied to the first story only; mobile home 290 cy single-wide, 415 cy double-wide; flooded personal property 25-30 cy slab on grade, 45-50 cy with a basement; other building = L x W x H x 0.33 / 27 cy; tons = structure cy / 2 + vegetative cy / wood factor.

Source and editionFEMA 329, Debris Estimating Field Guide (September 2010): single-family residence formula from the Hurricane Floyd study, vegetative cover multipliers and the first-story rule for multiple-story residences, the single-story table, mobile home figures, flooded personal property figures, the general building formula, and the USACE conversion factors; FEMA-325 (2007) Chapter 6 carries the same formulas.

Free accessFEMA 329 is a free federal field guide on fema.gov; every figure is a public-domain FEMA or USACE value.

What governsEstimate. AHJ and licensed professional govern.

API field namesstructure_type, structure_count, length_ft, width_ft, stories, height_ft, vegetation, wood_type, per_structure_cy, structural_cy, vegetative_cy

• VCM on the first story only for multiple-story residences the vegetation is computed as if S = 1FEMA 329 (2010)
• Floor area includes attached garages the total living space at and above ground level, measured from the foundation if the house is goneFEMA 329 (2010)
• 0.33 for air space the general building formula assumes a third of the building volume becomes debrisFEMA 329 (2010)