Table of Contents
What is control joint in construction?
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).
What is the purpose of a control joint?
The goal of the control joint is to allow the slab to crack, during expansion and contraction, in a known location and in a straight line. Expansion joints are put in place before the concrete is poured. Expansion joints are used to allow the slab to move and not put stress on whatever it abuts.
What is a control joint in concrete?
Contraction/Control Joints. Contraction/control joints are placed in concrete slabs to control random cracking. When shrinkage is restrained by contact with supporting soils, granular fill, adjoining structures, or reinforcement within the concrete, tensile stresses develop within the concrete section.
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.
Where do control joints go in concrete?
Control joints are generally placed into the concrete during the finishing process or within 24 hours of being poured.Control joints are commonly found in concrete: Garage floors. Driveways. Sidewalks. Patios. Basement floors. House slabs.
What is a control joint in drywall?
General: Control joints are predetermined separations that are designed to relieve internal stresses created by expansion and contraction of the gypsum board, commonly created from thermal or humidity movement, while external stresses are generally a result from physical movement of the structure.
Do you need expansion joints in concrete slabs?
Expansion joints are virtually never needed with interior slabs, because the concrete doesn’t expand that much—it never gets that hot. Expansion joints in concrete pavement are also seldom needed, since the contraction joints open enough (from drying shrinkage) to account for temperature expansion.
Do I need expansion joints in concrete driveway?
Concrete expansion joints are important for your sidewalk or driveway. Keeping your joints watertight will prevent moisture from seeping under concrete pads and causing them to heave or sink.
What is another name for a control joint?
Contraction joints (also sometimes called control joints).
How big can a concrete slab be without control joints?
Rule #1 – Keep joints as square as possible. Rule #2 – In order to prevent intermediate cracking, space joints (in feet) no more than 2 – 3 times the slab thickness (in inches).
What is the difference between a control joint and isolation joint?
Contraction or control joints also absorb some movement; however, their main function is to control the location and geometry of the natural cracking pattern in the concrete slab. Isolation joints isolate the pavement from a structure, another paved area, or an immovable object.
Are control joints structural?
Why are control joints used in slabs on grade but not on structural floors? Control joints are permissible because of the subgrade support. On structural slabs it is necessary for the concrete to be continuous between supports, thus making it impossible to use control joints.
Are control joints necessary?
There is a reason control joints are considered essential for whatever projects you have in design. Thermal expansion and contraction will occur in buildings – that’s a given – and control joints help prevent resulting cracks and damage. Control joints relieve these stresses by allowing for movement.
Is it too late to cut control joints?
WHEN TO SAW CONTROL JOINTS Cutting freshly poured concrete too late can lead to unwanted cracks in the concrete, rendering the joints ineffective. For most concrete work, cutting should take place within the first 6 to 18 hours and never beyond 24 hours.
Do concrete control joints need to be sealed?
Expansion joints need to be sealed periodically to protect against water, dirt, and debris. These elements can hurt the structural integrity of concrete over time. Water can also lead to mold and interior leaks that are costly to repair.
What are the seams in concrete called?
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.
How often are control joints in drywall?
Ceilings: in long expanses of ceilings at 30-foot intervals, with the drywall expansion joint extending the full width of the ceiling, from partition wall to partition wall. Technically, according to expert sources like National Gypsum, drywall movement control joints are recommended at intervals of 30 feet.
Does plasterboard need expansion gaps?
The gap is recommended for the edge of inside corner pieces that you need to cut. This is because if you cut it a little too wide, you can mess up the edge forcing it into place. It does NOT recommend gaps between full sheets.
What happens if you don’t put expansion joints in concrete?
If you have a concrete floor in your commercial building, you know expansion joints are necessary to allow for the natural expansion and contraction that occurs from temperature changes. Without these joints, large cracks can travel across your floor, creating costly damage.
