Inputs
Example data table
| Example | Type | Length (m) | Microstrain (µε) | Allowable (mm) | Movement (mm) | Suggested spacing (m) |
|---|---|---|---|---|---|---|
| Office corridor wall | Concrete block | 24 | 650 | 10 | 17.16 | 15.38 |
| Facade brickwork bay | Clay brick | 18 | 450 | 10 | 8.91 | 20.20 |
| AAC partition line | AAC | 30 | 300 | 8 | 9.90 | 24.24 |
| Stone veneer run | Stone | 20 | 150 | 8 | 3.30 | 48.48 |
Formula used
The calculator estimates drying shrinkage movement along a wall length using strain.
- Shrinkage strain = microstrain × 10-6
- Effective strain = strain × effective movement factor
- Movement (mm) = effective strain × length (mm) × safety factor
- Recommended spacing = allowable movement (mm) ÷ (effective strain × safety factor)
How to use this calculator
- Choose the masonry type, then review the suggested microstrain.
- Enter wall length, height, and thickness with your preferred units.
- Adjust effective factor if restraint will limit free movement.
- Set allowable joint movement based on joint and sealant design.
- Apply a safety factor for variability and construction tolerances.
- Press Calculate to view results above the form.
- Use Download CSV or PDF to save the latest calculation.
Professional overview
Masonry walls experience gradual volume change as moisture conditions stabilize after construction. This drying shrinkage is usually small in percentage terms, yet it can create meaningful movement over long runs. If the wall is restrained by returns, slabs, stiff frames, or heavy finishes, the strain may translate into cracking, debonding, or distress at openings. A practical way to manage this behavior is to anticipate the expected movement and distribute it through appropriately spaced movement joints and compatible sealants.
This calculator estimates linear shrinkage movement using shrinkage strain (microstrain), an effective movement factor, and a safety factor. Microstrain values are typically obtained from material data, testing, or project specifications. The effective movement factor lets you reflect restraint: values near 1.0 represent freer movement, while lower values reflect partial restraint or reduced strain transfer. The safety factor adds conservatism for variability in materials, curing, workmanship, and exposure conditions.
Example data: consider a 30 m concrete block wall with an assumed shrinkage of 600 µε, effective factor 1.00, and safety factor 1.10. The estimated total movement is approximately 19.8 mm along the wall length. If a joint or sealant system can reliably accommodate 10 mm of movement, the recommended spacing is about 15.15 m. That suggests one movement joint for a 30 m run, plus standard detailing at corners and openings. Use the example data table above to compare other materials and lengths quickly.
For professional use, treat this result as an early sizing check. Confirm microstrain values from your selected units, verify joint movement capability from manufacturer data, and coordinate joint layout with architectural modules, reinforcement, control joint requirements, and moisture barriers. Where finishes are brittle or tolerances are tight, consider closer joint spacing, improved slip details, or staged construction to reduce restraint. Always align final detailing with local standards, project specifications, and engineer-of-record guidance.
Quality joint layout is as important as the math. Place movement joints where stresses concentrate, such as changes in wall height, returns, long uninterrupted runs, and at interfaces with concrete frames. Keep joints continuous through finishes, provide compressible fillers, and avoid bridging with rigid plaster or tile. Where reinforcement is present, confirm whether joints should be full-depth or partial-depth control joints per project requirements. After construction, monitor early cracking during the first drying season, and maintain sealants promptly to preserve movement capacity. Document the assumed microstrain, joint widths, and installation checks so repairs follow the original intent.
FAQs
1) What is shrinkage microstrain?
Microstrain (µε) is shrinkage strain expressed in millionths. For example, 500 µε equals 0.000500 strain. It represents expected length change per unit length as masonry dries.
2) Does wall thickness affect shrinkage movement?
Thickness does not directly change linear movement from strain. However, thickness can influence restraint, stiffness, and cracking behavior, so keep it for context and coordination with structural and detailing decisions.
3) How do I choose the effective movement factor?
Use 1.0 for near free movement. Use lower values when the wall is strongly restrained by frames, returns, or slabs. If uncertain, start at 1.0 and run a sensitivity check at 0.7–0.9.
4) What allowable joint movement should I enter?
Enter the movement capacity you can confidently achieve with your joint width, sealant class, backing, and installation quality. Prefer manufacturer guidance and project standards over generic values.
5) Why is a safety factor included?
Shrinkage varies with moisture, curing, temperature, unit variability, and workmanship. A safety factor provides conservative allowance so joint spacing remains reasonable when real conditions differ from assumptions.
6) Can I use this for expansion as well?
This tool is focused on shrinkage movement. For thermal or moisture expansion, use expansion coefficients and temperature or moisture change ranges. You can still compare magnitudes to support joint design decisions.
7) What should I do if the suggested spacing is very small?
Review input strain, restraint, and allowable movement values first. If they are correct, plan more frequent joints, use joints with higher movement capacity, or introduce slip layers and details that reduce restraint.