When should control joints be cut?

When should control joints be cut?

Joints should be sawed as soon as the concrete can withstand the energy of sawing without raveling or dislodging aggregate particles. For most concrete work, cutting should take place within the first 6 to 18 hours and never beyond 24 hours.

Where are control joints required?

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.

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.

How often should control joints be placed in a sidewalk?

Usually, expansion joints should be no farther apart than 2 to 3 times (in feet) the total width of the concrete (in inches). So for a 4 inch thick concrete slab, expansion joints should be no more than 8 to 12 feet apart.

What is the difference between expansion joints and control joints?

In building materials, a control joint is used to control cracking while an expansion joint is designed to handle structural movement. A control joint can be formed during placement of the building material or cut after the material is placed.

How big can a concrete slab be without control joints?

Concrete control joints should be no less than ¼ of the total thickness of the slab (1” deep for a 4” thick pour) and placed no less than 2-3 times (in feet) the thickness (in inches) of the slab (8-12 feet apart for a 4” thick pour).

Do brick walls need expansion joints?

Structures that support the brick wythe on shelf angles, usually at each floor, must have horizontal expansion joints under each shelf angle. Larger sized expansion joints may be required to accommodate the differential movement of taller story heights or where a shelf angle supports more than one story of brickwork.

What happens if you don’t cut concrete?

Cutting too early can mark the pavement surface as well as cause joint raveling. Late sawing can result in random concrete cracks. Shallow cracks aren’t sufficient to prevent uncontrolled cracking while deep cuts are excessively labor intensive and undermine the aggregate interlock in the concrete.

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.

Does all concrete need expansion joints?

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.

Where do you put expansion joints?

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. These joint are placed where a slab meets a building, where a slab meets another slab, and where a pool deck meets the coping.

Do I need expansion joints in a concrete slab?

All concrete will shrink slightly as it dries and, when it’s set, will expand or contract depending on the ambient temperature. To prevent cracks from forming, concrete expansion joints should be incorporated to allow for movement, particularly in slabs with a surface area exceeding 6m2.

When to know when to saw control joints?

When to Saw Control Joints. Sawcut depth is up to 13/8 inch and sawcut widths range from a 1/8-inch straight groove to a 1/2-inch T-cut. Electric-powered lightweight models use a smaller-diameter saw blade and cut notches 3/4- to 1-inch deep at sawing speeds of 4 to 11 feet per minute. For more information on these saws,…

When to reduce the spacing of Control joints?

If Type II nonmoisture-controlled units are used, reduce the control joint spacing. In such cases, James Amrhein, in his book, Reinforced Masonry Engineering Handbook for Clay and Concrete Masonry, recommends reducing control joint spacing by as much as one-half.

When to cut the control joints in concrete?

WHEN TO CUT CONTROL JOINTS Make sure you are cutting joints soon enough. In hot weather, concrete might crack if joints are not cut within 6-12 hours after finishing concrete.

How tall should control joints be on a wall?

Thus, for a 10-foot-high wall, control joints should be placed 20 feet on center. If joint reinforcing is used, the spacing can be increased as shown in the table. Note that the recommendations in the table are for Type I moisture-controlled units. If Type II nonmoisture-controlled units are used, reduce the control joint spacing.