Fire Rating Estimate Calculator

Project / Area Name

Optional label for exports and history.

Date

Used for record keeping.

Assembly Type

Choose the closest assembly category.

Primary Material System

Estimator uses different base curves by system.

Main Thickness (mm)

For boards, use stud depth or overall assembly depth.

Total Board Layers (all exposed faces)

Example: 2 layers each side ⇒ 4 total.

Stud / Framing Type

Only impacts stud-and-board systems.

Cavity Insulation

Mineral wool can help; foam may reduce performance.

Additional Protection Thickness (mm)

For fireproofing, wraps, or protection boards.

Penetrations (count)

Includes pipes, conduits, boxes, and sleeves.

Openings (% of area)

Glazing, grilles, vents, large cut-outs, access panels.

Firestopping Quality

Continuity at penetrations is a major driver.

Fire Exposure Sides

Two-sided exposure can reduce lining effectiveness.

Work Quality & Continuity

Small gaps can erase large material gains.

Unknowns / Voids / Moisture

Uncertainty reduces confidence and expected rating.

Target Rating (minutes)

Examples: 30, 60, 90, 120 minutes.

Safety Margin (0.00–0.40)

Reduces the estimate to be more conservative.

Result appears above this form after submission.

Example Data Table

Sample scenarios to show how inputs influence the estimate. Values are illustrative only.

Scenario	System	Thickness (mm)	Layers	Penetrations	Openings	Protection	Estimated (min)
Office Partition	Stud + board, mineral wool, basic stopping	100	4	6	10%	0	≈ 75
Concrete Stair Core	Reinforced concrete	150	0	2	0%	0	≈ 180
Mechanical Shaft Wall	Stud + board, good stopping, two-sided exposure	125	6	18	5%	0	≈ 120
Steel Column Upgrade	Steel baseline with added protection	20	0	0	0%	25 mm	≈ 95

Formula Used

This calculator estimates fire resistance time (minutes) using a simple scoring model:

Base minutes come from the selected material system and thickness.
Additions include lining layers, protection thickness, insulation, and continuity quality.
Penalties subtract minutes for penetrations, openings, and uncertainty.
Safety margin reduces the result to be conservative.

Estimated Minutes = clamp( Base(material, thickness) + Adds(layers, insulation, protection, quality) − Penalties(openings, penetrations, unknowns) ) × (1 − SafetyMargin)

The model is intentionally transparent for quick comparison. Use tested assemblies and professional review for final decisions.

How to Use This Calculator

Select the closest assembly type and material system.
Enter thickness and total board layers across exposed faces.
Choose framing, insulation, and any added protection thickness.
Estimate penetrations and openings percentage realistically.
Set firestopping and work quality based on what is installed.
Add a target minutes value to see if you meet it.
Use a safety margin when inputs are uncertain.
Submit to view results above the form, then export CSV/PDF.

Why estimates help early decisions

Early design teams often need a quick sense of how long a wall, slab, or protected steel member may resist fire exposure before detailed listings are selected. This estimate supports preliminary budgeting, coordination, and risk screening. For example, a 60 minute target can guide whether a typical partition should be upgraded with additional layers, improved stopping, or protection on a steel element. Use it during design and procurement planning.

Inputs that change resistance time

The strongest drivers are material system, thickness, and continuity. Concrete and masonry generally gain minutes with added thickness, while stud-and-board assemblies rely heavily on total layers across exposed faces. Openings and penetrations reduce performance because they introduce weak paths for heat and smoke. Work quality and verified firestopping also matter, especially around boxes, sleeves, and joint intersections.

How the estimate is calculated

The calculator combines a base curve for the chosen material and thickness with additions for lining layers, insulation choice, and added protection thickness. It then subtracts penalties for penetrations, opening percentage, and uncertainty. The result is clamped to practical bounds and reported in minutes and hours. This transparent structure makes sensitivity checks easy: change one input and see the impact.

Interpreting targets and safety margin

Set a target rating to compare the estimated minutes against a required level, such as 30, 60, 90, or 120 minutes. Add a safety margin when inputs are uncertain or workmanship varies; a 0.10 margin reduces the reported value by 10 percent. Use this feature to keep decisions conservative, especially when drawings change or MEP routing adds new penetrations.

Limitations and field documentation

This tool does not replace certified assemblies, lab tests, or local code review. Treat results as directional and document assumptions: thickness source, layer counts, penetration estimates, and firestopping scope. For higher confidence, align selections with tested systems and record product data sheets, detailing notes, and inspection photos. Exporting CSV and PDF helps maintain an auditable trail across revisions.

FAQs

1) Is the estimate a certified fire rating?

No. It is a planning estimate based on general behavior and continuity factors. Use listed, tested assemblies and local requirements for compliance and permitting.

2) Which inputs usually move the result the most?

Material system, thickness, and total lining layers have the biggest effect. Penetrations, openings, and poor firestopping can quickly reduce minutes, even when materials are upgraded.

3) How do I enter board layers correctly?

Enter the total layers across all exposed faces. For two layers on each side of a partition, enter four layers in the field.

4) What does the safety margin do?

It reduces the reported minutes by a chosen percentage to stay conservative. Use a higher margin when access is limited, workmanship is uncertain, or the design is still changing.

5) Can I use this for doors and glazing?

Only as a rough indicator. Doors and glazed systems depend on specific listings, hardware, seals, and frame details. Always select products with tested ratings that match the required duration.

6) What should I keep with the export files?

Record assumptions, drawings, product data sheets, and inspection notes. Track changes in penetrations and openings across revisions so the estimate remains comparable and auditable.

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