It’s worth mentioning whether you’re using reinforcement. My rule of thumb is squares up to 12′ don’t need control joints (similar to ecnerwal) but rectangles do when the length is more than 150% of the length or a 4 foot wide pad longer than 6′ needs a control line since this is 8′ I would put one at 4′.
Do small concrete slabs need expansion joints?
Concrete expansion joints give the slabs just enough room to move which helps prevent cracks & buckling. Without these joints, even a little movement creates pressure and stress on the concrete. Eventually weak spots can crack or buckle.
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).
Does a slab need control joints?
Early-entry saws are available which may allow cutting to begin within a few hours after placement. Contraction/control joints must be established to a depth of ¼ the slab thickness (Figure 2). Proper joint spacing and depth are essential to effective control of random cracking.
Do you have to cut control joints in concrete?
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.
What size concrete slab needs an expansion joint?
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.
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.
How far apart should the control joints be for a 6 slab?
12 to 15 ft.
Rule #5: For better crack control keep the maximum distance between joints in feet at 2 to 2.5 times the slab thickness in inches. For a 6 in. thick slab, the maximum joint spacing should be limited to 12 to 15 ft. Exceeding a joint spacing of 15 ft.
Where do you need expansion joints in concrete?
Concrete expansion joints are particularly important where there have been consecutive concrete pours and are also useful when laying concrete within an area bordered by walls or buildings or if objects such as manhole covers need to be incorporated.
What is the difference between a control joint and a construction joint?
Control joints focus the cracking so that it’s not ugly or dangerous. Construction joints are interruptions in the slab between different pours of concrete. Since you can’t pour concrete non-stop, there is a break between sections of the pour. Each time you stop the pour, you get a construction joint.
What happens if you don’t cut concrete?
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.
How often should you cut control joints in concrete?
Cuts should be approx. 2-3 times the thickness of your slab in feet. For example, a 6” slab would have cuts 12′ – 18′ apart. This is strictly a guideline to work from.
Where do you cut control joints in concrete slab?
Cut joints 25% of the depth of the slab. A 4″ thick slab should have joints 1″ deep. Groover tools cut joints in fresh concrete. Saw cutting cuts joints as soon as the concrete is hard enough that the edges abutting the cut don’t chip from the saw blade.
What is the difference between control joint and expansion joint?
Control joints can be isolated within the plane being treated (brick facades, concrete sidewalks) while expansion joints must bisect the entire structure thereby creating a gap throughout all of the building elements—foundation, walls, curtainwalls, plaza decks, parking decks, floors, and roof.
Do you need expansion joints in a garage floor?
Many people understand that wood shrinks and expands as temperature and humidity ebb and flow through the year. But the same thing happens with concrete. That’s why it is necessary to include expansion joints along the edges of the concrete garage floor as well as around posts or other protrusions in the slab.
Do you need expansion joints in concrete sidewalk?
A.: According to several industry sources, expansion joints, even at 50-foot intervals, are not necessary for the sidewalk project. Long stretches of concrete do not require intermediate expansion joints.
What is the purpose of control joints in concrete?
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.
How far apart should concrete joints be?
The following recommended tips should be observed: Maximum joint spacing should be 24 to 36 times the thickness of the slab. Joints should be spaced about 10 feet and a maximum of 15 feet. When using joint groove for contraction joints, the joint should be a minimum depth of 1/4 thickness of the slab.
Should concrete control joints be caulked?
Caulking Concrete Cracks and Expansion Joints
Caulking the joints and cracks is the best way to stop this from happening. Even expansion joints in your concrete driveway should be caulked. They can be the biggest culprit of water under your slabs.
Is expansion joint necessary?
Expansion joint failure can happen for several reasons, but regardless concrete needs a buffer as it goes through the natural cycles of expansion and contraction. So, this has always been the case, and this is why expansion joints are necessary.
How do you seal concrete slab joints?
Quote from the video:
Quote from Youtube video: You want to place a backer rod a foam cell backer rod in between the expansion joint.
