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Selected Northwest Details: Expansion And Contraction Joint Details - Masonry Control Joints
1) General
2) Details
1. Control Joints
Control joints are employed in crack control to reduce restraint by accommodating movement of the masonry wall, or movement of structural elements adjacent to the wall. They are vertical or horizontal separations built into the wall at locations where cracking is likely due to excessive horizontal stress or due to expansion of brick. Their spacing along the wall length will depend upon: (1) expected movement(s) of wall or other elements, (2) resistance of wall to horizontal tensile stress, and (3) the extent and location in the wall of windows, doors, recesses, chases, and other causes of stress concentration. Control joints may be used alone for crack control or they may be used in conjunction with either or both bond beams and joint reinforcement.
Common methods of constructing control joints are illustrated the following pages. The joints permit free longitudinal movement, but they should have sufficient shear and flexural strength to resist lateral loads. They also must be weathertight when located in exterior walls.
Locations for control joints include:
1. Changes in wall height or thickness.
2. At construction joints in foundation, in roof, and in floors.
3. At chases and recesses for piping, columns, fixtures, etc.
4. At abutment of wall and columns.
5. At return angles in "L", "T", and "U" shaped structures.
6. At one or both sides of wall openings.
Generally, a control joint is placed at one side of an opening less than six feet in width and at both jambs of openings over six feet wide. Control joints can be omitted if adequate tensile reinforcement is placed above and below wall openings.
Where concrete masonry is used as backup of brick:
1. Extend control joints through facing if it is rigidly bonded (masonry bond).
2. Control joint need not extend through facing when bond is flexible (metal ties).
Control joint should extend through plaster applied directly to masonry units. Plaster applied on lath which is furred out from masonry may not require vertical separation at control joints.
Provide horizontal slip plane where reinforced lintel beam terminates at a control joint. Provide horizontal slip plane at junction of roof and load-bearing masonry terminating at a control joint. Bond between roof and wall should be broken 12-15 feet back from corners, with slip plane.
Differential movement only creates problems if excessive stress is allowed to develop. Flexible anchorage, expansion and contracting joints, reinforcement counteract or relieve excessive stresses.
Thermal Expansion Coefficients Table of Various Building Materials
| Material | Average coefficient of lineal thermal expansion X 10-6 (in/F) | Thermal expansion, [in. per 100ft for 100F temperature increase (to closest 1/16-in.) |
| Clay Masonry | ||
| Clay or shale brick | 3.6 | 0.43 (7/16) |
| Fire clay brick or tile | 2.5 | 0.30 (5/16) |
| Clay or shale tile | 3.3 | 0.40 (3/8) |
| Concrete Masonry | ||
| Dense aggregate | 5.2 | 0.62 (5/8) |
| Cinder aggregate | 3.1 | 0.37 (3/8) |
| Expanded-shale aggregate | 4.3 | 0.52 (1/2) |
| Expanded-slag aggregate | 4.6 | 0.55 (9/16) |
| Pumice or cinder aggregate | 4.1 | 0.49 (1/2) |
| Stone | ||
| Granite | 4.7 | 0.56 (9/16) |
| Limestone | 4.4 | 0.53 (1/2) |
| Marble | 7.3 | 0.88 (7/8) |
| Concrete | ||
| Gravel aggregate | 6.0 | 0.72 (3/4) |
| Lightweight, structural | 4.5 | 0.54 (9/16) |
| Metal | ||
| Aluminum | 12.8 | 1.54 (1-9/16) |
| Bronze | 10.1 | 1.21 (1-3/16) |
| Stainless Steel | 9.6 | 1.15 (1-1/8) |
| Structural Steel | 6.7 | 0.80 (13/16) |
The NW Masonry Guide Table of Contents
Masonry Institute of Washington
Washington State Conference of Mason Contractors
