Manufactured Home Diagonal Tie-Down Anchor Count

ScopeManufactured homes are the housing most damaged by wind, and the temporary housing units FEMA places after a disaster are installed to the same federal standard. 24 CFR 3285.402 does the engineering for the common cases and prints the result as a maximum diagonal tie-down strap spacing, by wind zone, nominal floor width, strap attachment height, main I-beam spacing, and in Zones II and III the near-beam or second-beam method. The calculator looks up the cell in Tables 1 to 3, places a strap within 2 ft of each end as the table note requires, and fills the length between at no more than the tabulated spacing. A single-section 14 ft wide home 66 ft long with straps at 25 in and 82.5 in beam spacing has 62 ft between end straps: at 18 ft 2 in in Zone I that is 5 anchors per side and 10 in all; at 7 ft 7 in in Zone II, 10 per side, 20 in all, plus 20 vertical ties; at 6 ft 2 in in Zone III, 12 per side and 24, plus 24 vertical ties -- the same home more than doubled. Cells the regulation marks N/A are refused by name, not extrapolated. The tables assume anchors certified to a 3,150 lb working load, a 90 in sidewall, a 20 degree roof pitch, and a 30 to 60 degree strap angle, and do not apply in flood or seismic hazard areas, where the anchorage is engineered. It does not cover longitudinal anchorage, soil class certification, frost depth, homes within 1,500 ft of the coast, or piers. 24 CFR 3285, the manufacturer's installation instructions, the licensed installer, and the state administrative agency govern.

Formula or tablemaximum diagonal strap spacing s from 24 CFR 3285.402 Table 1, 2, or 3 by wind zone, floor width, strap height, I-beam spacing, and (Zones II, III) method; per side = ceil((length - 2 x 2 ft) / s) + 1; total = 2 x per side x sections; vertical ties at every diagonal location in Zones II and III; N/A cells refused.

Source and edition24 CFR 3285.402, Tables 1-3 and notes (maximum diagonal tie-down strap spacing, Wind Zones I-III), and 3285.402(a)(2) (3,150 lb working, 4,725 lb ultimate anchor load); transcribed from the regulation. The manufacturer's installation instructions, the installer, and the state administrative agency govern.

Free access24 CFR 3285 is federal regulation in the public domain; the tables are transcribed and were checked cell by cell against the Cornell LII copy on 2026-09-30.

What governsEstimate. AHJ and licensed professional govern.

API field nameswind_zone, floor_width_row, home_length_ft, strap_height_row, beam_spacing_row, method, sections, max_spacing_in, anchors_per_side, total_anchors, vertical_ties

• Anchor capacity 3,150 lb working load; a lower rating requires closer spacing24 CFR 3285.402 table notes
• End straps a strap within 2 ft of each end of the home24 CFR 3285.402 table notes
• Table limits 90 in sidewall, 20 degree roof pitch, 30-60 degree strap angle, no flood or seismic hazard area24 CFR 3285.402 table notes