Control joints are typically required in exposed above grade concrete masonry walls, where net aesthetic shrinkage cracking may detract from the appearance of the wall, and to limit moisture or air infiltration. Shrinkage cracks in concrete masonry are not a structural concern.
Where do control joints go in masonry walls?
In vertically reinforced masonry walls with masonry lintels, vertical control joints should be located between openings, or at least 24-inches away from the opening – not to exceed 25-feet on-center (Figure 1).
What are control joints used for in masonry?
Control joints are used to relieve stress induced by small amounts of movement caused by shrinkage during curing or small expansion and contraction movements as the result of absorption and expulsion of moisture in concrete or masonry (brick, CMU, etc).
How often do you need control joints in masonry walls?
A: When no joint reinforcing is used, National Concrete Masonry Association (NCMA) TEK 53, “Design of Concrete Masonry for Crack Control,” recommends spacing control joints in straight wall sections without openings no farther apart than twice the height of the wall, 40 feet maximum.
Why are control and expansion joints required in masonry walls?
Expansion joints must be located so that the structural integrity of the brickwork is not compromised. A control joint determines the location of cracks in concrete or concrete masonry construction due to volume changes resulting from shrinkage.
Where do you put a control joint?
Normally, horizontal control joints are placed every floor over the windows. However, they could also be placed at every floor line with loose lintels over the windows. The control joint could be spaced every two floors, however, the size of the shelf angle and the width of the joint would have to be larger.
What type of joint is typically required in a concrete masonry wall?
Control joints
Control joints are typically used in concrete masonry to reduce the occurrence of shrinkage-related cracking. A control joint is a continuous vertical joint filled with mortar, but with a bond breaker on one side so that tensile stress cannot develop across the joint.
What is the difference between a construction joint and a control joint?
Both isolation and construction joints are formed before the concrete is poured; contraction joints (or control joints) are “placed” in the fresh concrete before it has a chance to create its own joints—also known as cracks.
What are some common reasons that masonry structures fail?
What Are the Most Common Causes of Masonry Damage?
- Moisture Penetration. One of the biggest threats to a masonry structure is moisture.
- Cracking. Cracks are a common problem with masonry construction.
- Staining. Staining is a big problem for exterior-facing masonry walls.
- Bond Failure.
- Displacement.
- Spalling.
What is the purpose of control joint?
Control joints are preplanned cuts in concrete that help control where and how cracks appear in poured concrete. Concrete shrinks as it cures and will change in response to temperature. A large area of poured concrete is likely to crack, especially when up against a foundation or street curb.
What is a controlled joint?
WHAT ARE CONTROL JOINTS? Control joints are planned cracks which allow for movements caused by temperature changes and drying shrinkage. In other words, if the concrete does crack-you want to have an active role in deciding where it will crack and that it will crack in a straight line instead of randomly.
What is the purpose of joint reinforcement in masonry walls?
There are multiple uses for joint reinforcement in masonry structures. Joint reinforcement can be used to provide crack control, horizontal reinforcement, and bond for multiple wythes, corners and intersections. The following list highlights only those requirements specific to joint reinforcement.
What is spacing for control joints for retaining wall?
Control joints are spaced at 30′ but in the stem only. We don’t run the bars through the control joints. RE: Reinforced Concrete Retaining Wall – Specifications for expansion joints? Control joints are spaced at 30′ but in the stem only. We don’t run the bars through the control joints.
What is the spacing of concrete slab control joints?
Recap On Cutting Concrete Control Joints Control Joints are not intended to stop cracking but rather control cracking It is best to cut joints as early as possible either while finishing with a concrete groover or within 6-18 hours after finishing with a concrete saw. Plan out your control joint spacing 24-36 times the depth of your concrete slab
What are Masonry movement joints?
Movement joints such as control joints are one method used to relieve horizontal tensile stresses due to shrinkage of the concrete masonry units, mortar, and when used, grout. They are essentially vertical planes of weakness built into the wall to reduce restraint and permit longitudinal movement due to anticipated shrinkage, and are located where stress concentrations may occur.
