Masonry Magazine January 1966 Page. 41
weather tight when located in exterior walls.
Table I gives L/H ratios for walls without openings that are constructed of Type "H" Q BLOCK concrete masonry units. Other 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 other materials:
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.
TABLEI
CONTROL JOINT SPACING FOR MOISTURE CONTROLLED, TYPE I, Q BLOCK UNITS
| Recommended Spacing of Control Joints | Vertical Spacing of Joint Reinforcement |
| --- | --- |
| | None | 24" | 16" | 8" |
| Expressed as Ratio of Panel Length to Height L/H | 2 | 2½ | 3 | 4 |
| With Panel Length (L) Not to Exceed [Regardless of Height (H)3 | 40' | 45' | 50' | 60' |
| NOTE: When bond bean spaced vertically armed in of joint reinforcement, corest joints may be spaced 60 maximum. | |
AT INTERSECTING WALL CHANGE IN WALL HEIGHT OVER OPENING AT PILASTER FIG. 3 TYPICAL CONTROL JOINT LOCATIONS OVER OPENING
LOCATION OF JOINT REINFORCEMENT
1. Place in first and second bed joints immediately above and below wall openings.
2. Joint reinforcement at openings should extend not less than 24 inches, or to the end of the panel, whichever is the smaller.
3. Place in two or three courses immediately below the top of the wall.
4. Joint reinforcement need not be located closer to a bond beam than 24 inches.
5. Joint reinforcement should be interrupted at control joints and at expansion joints.
6. Joint reinforcement is not required between openings where the relationship of distance between openings (L) and opening height (H) is not more than shown in Table I in the column marked "none" for joint reinforcement.