Movement joints
Expansion joints of clay brick masonry and control joints of concrete masonry: the movement of the wall over the joint spacing, the strain it puts on the sealant in extension and compression, the joint width needed and the largest spacing a joint width allows, with the spacing limits of the industry guides. US and metric units; a serviceability calculation, so there is no strength or allowable stress switch.
Edition and sources. The movement coefficients are those of TMS 402 4.2.3 to 4.2.5 (read in the 402-16 text; the numbering is unchanged in 402-22). BIA Technical Notes 18 and 18A and CMHA TEK 10-2C and 10-3 are not on hand: the closing formula of brick expansion joints, the freezing expansion coefficient, the 25 ft brick spacing and the TEK 10-2C empirical criteria are written from knowledge and marked "to confirm against the code text" in the steps. Every one of them is an input you can change.
Inputs of the movement joints #
- Wall and joints: clay brick (expansion joints) or concrete masonry (control joints); the wall length (for the number of joints) and height; the joint spacing and width; the minimum joint width (3/8 in. prefilled); the sealant's ASTM C920 class (±25, ±35, ±50 or +100/−50 percent).
- Temperatures: the rise of the wall temperature above its installation temperature and the drop below it (of the wall, not the air; dark walls in the sun run hotter).
- Clay: the thermal coefficient (4 × 10⁻⁶ /°F, TMS 402 Table 4.2.3), the moisture expansion (300 × 10⁻⁶, 4.2.4), the freezing expansion (200 × 10⁻⁶ where brick freezes wet, BIA TN 18; 0 in mild climates) and your spacing limit (25 ft, BIA TN 18A).
- Concrete masonry: the thermal coefficient (4.5 × 10⁻⁶ /°F), the drying shrinkage εs of the units (0.065 %, the ASTM C90 maximum; km = 0.5 εs, 4.2.5.1), the panel length-to-height limit and the spacing limit (1.5 and 25 ft, TEK 10-2C) and the horizontal reinforcement per foot of height.
Auto-design (editor toolbar) varies the joint spacing and width. Objective: the fewest joints, then the narrowest. The wall, temperatures, coefficients, sealant class and spacing limits are kept.
Checks performed #
| Check | Basis |
|---|---|
| Sealant compression | Clay: Δc = (ke + kf + kt ΔT) S with ΔT the full temperature range (BIA TN 18A form); concrete masonry: Δc = kt ΔT_rise S. Δc / w at most the compression capability |
| Sealant extension | Clay: Δo = kt ΔT_drop S (moisture expansion is irreversible); concrete masonry: Δo = (km + kt ΔT_drop) S. Δo / w at most the extension capability |
| Joint width | At least the minimum entered |
| Joint spacing | Clay: at most your limit; concrete masonry: at most min(ratio × H, limit) (TEK 10-2C empirical criteria) |
| Horizontal reinforcement (concrete masonry) | Advisory: the empirical spacing assumes at least 0.025 in.²/ft of height |
Results: the required joint width, the largest spacing for the width entered and the number of joints in the wall. The drawing is the wall elevation with the joints.
Limitations #
- Joints are located at regular spacing; the joints at openings, corners, offsets, changes of height and at the ends of shelf angles (BIA TN 18A, TEK 10-2C) are yours.
- The sealant depth, backer rod, bond breaks, shelf angles, ties and the shear transfer across control joints are not designed.
- Restraint (the wall's friction on its base or flashing) is not credited: the free movement is used.
- The engineered method of TEK 10-2C (spacing from the amount of horizontal reinforcement) is not built in.
Verification examples #
Verification status: 11 values compared in 2 examples (0 published, 2 hand calculations from the cited equations): 11 within tolerance, 0 recorded deviations. No published example: every value is a hand calculation. That checks the program against this reading of the code, not the reading itself. Code basis: not yet recorded for this module.
No published example is on hand: hand calculations of the closing, opening, sealant strains, required width and largest spacing for a brick wall and a concrete masonry wall. BIA TN 18 / 18A and CMHA TEK 10-2C / 10-3 are listed as documents needed; when they arrive, the formula, kf and the spacing limits are to be compared.