Expansion Joint Gap Calculator

Calculate sealant volume, packing depth, and system type for expansion joint firestop based on gap width and movement.

Inputs

Gap width (in)

Joint length (ft)

Expected movement (in)

Fire rating (hrs)

Gap depth (in)

Tab to move between fields

Results

Width-to-depth ratio

2

Movement (%)25%

Packing depth (in)5

Sealant volume (fl oz)398.9

Cartridges (20 oz)20

System type (1-3)2

Material Cost$236.04

How to Use This Calculator

Enter Gap width (in), Joint length (ft), and Expected movement (in).
Set Fire rating (hrs) and Gap depth (in).
Review the Width-to-depth ratio result.
Use Movement (%) (%) and Packing depth (in) to inform your decision.

What each input means

Gap width (in): Current width of the expansion joint gap.
Joint length (ft): Total linear feet of expansion joint.
Expected movement (in): Maximum expected joint movement.
Fire rating (hrs): Required fire resistance rating.
Gap depth (in): Depth of the gap from surface to bottom.

What each result means

Width-to-depth ratio: Sealant width vs depth ratio (target 2:1).
Movement (%): Movement as percentage of gap width.
Packing depth (in): Mineral wool packing depth behind sealant.
Sealant volume (fl oz): Total firestop sealant needed.
Cartridges (20 oz): Sausage packs needed.
System type (1-3): 1 = Standard, 2 = Flexible, 3 = Bellows/composite.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Gap width (in) = 2, Joint length (ft) = 30, Expected movement (in) = 0.5, Fire rating (hrs) = 2 = 5 input(s) provided
Calculate Width-to-depth ratio
Width-to-depth ratio
2 = 2
Calculate Movement
Movement
25 = 25%
Calculate Packing depth
Packing depth
5 = 5

Engine last updated August 5, 2026.

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