Plan a secure refuge with clear construction inputs. Estimate space, ventilation, and material quantities easily. Export results instantly for crews, budgets, and compliance today.
| Scenario | Occupants | Hazard | Duration (h) | Planned Size (ft) | Wall/Roof (in) |
|---|---|---|---|---|---|
| Residential interior safe room | 6 | Tornado | 8 | 8 × 10 | 8 / 8 |
| Small site command refuge | 12 | Hurricane | 24 | 12 × 14 | 10 / 10 |
| Security upgrade room | 4 | Ballistic | 6 | 7 × 9 | 8 / 8 |
Floor area is calculated from occupants, a selected area-per-person value, and an allowance factor. For quick planning, many teams target 5 sq ft/person for short tornado sheltering and 10 sq ft/person for longer hurricane refuge. Add 10–20% allowance for circulation, seated posture, storage, and door swing clearance.
Ventilation flow is based on occupants multiplied by a CFM-per-person target, then increased by a safety factor. A practical planning range is 10–20 CFM/person depending on filtration, duct losses, and occupancy density. For projects that include filters or backdraft dampers, a 1.10–1.30 multiplier helps maintain airflow under resistance.
Wall and roof quantities are derived from room perimeter, ceiling height, and selected thicknesses. The tool converts cubic feet to cubic meters using 0.0283168466. Rebar is estimated using a density (kg/m3) multiplied by concrete volume. Many preliminary budgets start near 100–150 kg/m3, then refine with structural design detailing.
Anchors are estimated as perimeter divided by spacing. Typical concept spacing is 1.5–3.0 ft, but final spacing depends on load path, substrate condition, and tested assembly requirements. Door type should match the hazard: impact-rated for wind events, ballistic-rated where required, and fire-rated where separation is needed.
Total cost combines concrete, rebar, door, ventilation allowance, and supplies, then applies labor and contingency percentages. Early estimates often use 15–25% labor and 5–15% contingency to cover detailing, logistics, and regional price spread. After schematic design, replace unit allowances with vendor quotes for accuracy.
The score is a planning index from 0 to 100. It combines thickness, ventilation per person, space adequacy, and door type. It is not a certification and should never replace tested assemblies or code-based design.
No. If you leave dimensions blank, the tool assumes a square room sized to the target area. Enter length and width when you already have a floor plan and want quantities based on that layout.
Allowance adds practical margin for circulation, seating, stored supplies, and door swing clearance. It also covers irregular layouts where some area is not usable. Typical factors range from 1.10 to 1.20.
Start with 10–20 CFM per person for preliminary planning, then refine based on filtration, fan capability, and local standards. Use the safety factor to account for pressure drop across filters and louvers.
No. They are early estimates based on simple geometry and density assumptions. Final quantities should come from structural drawings, including openings, laps, splices, and reinforcement layout for walls, roof, and connections.
Include supply, frame, hardware, installation labor, sealants, and any testing requirements. For ventilation, include fans, ducts, louvers, dampers, filters, controls, and electrical connections if applicable.
Yes, as a conceptual estimator. Increase inputs for duration, occupancy, and equipment needs. For regulated facilities, confirm required standards, tested assemblies, and inspection requirements before using results for procurement or permitting.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.