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.
How often do you need control joints in masonry?
The National Concrete Masonry Association (NCMA TEK 10-2C) recommends that control joints be spaced at 25 feet or 1.5 times the height of the wall, whichever is less.
What is a control joint in masonry wall?
Control joints in masonry are vertical weak planes intentionally built or cut into masonry to control where cracking occurs. Control joints should be installed in any masonry assembly that expected to experience net shrinkage over time. Usually, we think of control joints in concrete masonry (CMU).
What are control joints in a house?
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 do control joints work?
Contraction joints (sometimes called control joints) are used in unreinforced and lightly reinforced slabs-on-ground to minimize random cracking. By creating straight-line weakened-planes in concrete, contraction joints “control” the cracking location by inducing cracks at predetermined locations.
Are control joints required in masonry walls?
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.
Why a control joint is necessary?
IMPORTANCE OF CONTROL JOINTS Placing control joints in a slab will help keep cracks from becoming visually noticeable and spreading. In an ideal pour and control joint location, any cracks formed by concrete shrinking will actually occur inside the control joint.
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.
Why are control joints used?
What is the difference between control joint and construction 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 is control joint in construction?
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. If control joints are not provided, a concrete masonry wall may crack as it shrinks over time.