Set joint openings that match real conditions. Compare hot and cold gaps with safety checks. Download a clear report for design and site records.
| Scenario | Material | Run (m) | Tmin / Tmax / Tinstall (°C) | Joints | Other move (mm) | Recommended gap (mm) |
|---|---|---|---|---|---|---|
| Parking slab strip | Concrete | 30 | 0 / 40 / 20 | 1 | 2 | ≈ 48.40 |
| Steel walkway bay | Steel | 18 | -5 / 45 / 15 | 2 | 1 | ≈ 23.08 |
| Aluminum canopy run | Aluminum | 12 | 5 / 55 / 25 | 1 | 1.5 | ≈ 33.00 |
Thermal movement is estimated using linear expansion:
ΔL = α × L × ΔT
For multiple joints, the calculator assumes thermal movement is shared evenly:
ΔL_per_joint = ΔL_total / N
Directional allowances include additional movement and safety factor:
Allowance = (Thermal + Other) × (1 + Safety%)
Sealant movement capability limits allowable movement each direction:
Movement ≤ (Capability%) × JointWidth
Expansion joints control length change caused by daily and seasonal temperature swings. The calculator converts your run length to millimeters, applies a material coefficient, and evaluates movement from the installation temperature to the hottest and coldest service temperatures. When the element warms, the joint must compress without bottoming out. When it cools, the joint must open without tearing the seal.
Long elements often include multiple joints between fixed points or anchors. This tool assumes the total thermal movement is shared evenly across the number of joints entered. That assumption is appropriate for repeating joints with similar stiffness and restraint. If one joint is stiffer, closer to an anchor, or partially blocked, it may attract more movement and should be checked separately.
Real projects include more than temperature effects. Settlement, drying shrinkage, creep, racking, and construction tolerances can change the joint width. The “other movement” input is added as a worst case in both directions, then a safety factor increases the movement allowances. The reported compression and opening allowances are the values your joint system should accommodate reliably.
Sealants are commonly rated by percent movement relative to joint width. The calculator converts that rating into a movement limit per direction and computes the minimum joint width that satisfies both compression and opening demands. The recommended install gap also respects a minimum constructible gap so backer rod, tooling, and bond breaker details remain practical. Where restraint conditions differ, consider adding joints or using slip details to limit stress in adjacent components.
Use the hottest and coldest predicted gaps to confirm that joint edges, fillers, plates, or covers have adequate clearance. Compare the movement range with product data for sealants, fillers, and cover assemblies, and document assumptions in submittals. During inspection, verify joint cleanliness, correct depth-to-width ratio, and that obstructions are removed before sealing.
Enter the continuous length between fixed points such as anchors, corners, or stiff diaphragms. If the element can freely slip at one end, use the restrained length that actually builds force and drives joint movement.
Use the preset for common materials or enter a value from the project specification or manufacturer data. For composites, select a conservative coefficient that matches the dominant material in the movement direction.
Joint width is set when the work is installed. The calculator measures expansion and contraction from that baseline, so the hottest and coldest gaps reflect the same day the joint was formed or sealed.
It represents non-thermal effects per joint, such as shrinkage, settlement, racking, or fabrication tolerance. The tool adds it to both opening and compression as a worst-case allowance for planning.
Use the product’s rated movement class or percent movement, then enter the corresponding value. If durability is critical, choose a conservative rating and include a safety factor to reduce the risk of early failure.
They are an estimating and documentation aid. Always confirm joint geometry, substrate restraint, edge strength, and sealant detailing with project requirements and a qualified professional, especially for critical structures or unusual exposure.
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.