Table of Contents
Can you add expansion joints after concrete is poured?
You can install concrete expansion joints before or after the concrete is laid.
How far apart should expansion joints be in concrete?
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.
Do you need expansion joints in concrete?
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.
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.
How big can a concrete slab be without expansion 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).
Why do they cut lines in concrete?
To prevent sidewalks from cracking in random spots and breaking apart, builders make lines in sidewalks. The technical term for sidewalk lines is contraction joints. Contraction joints are placed in fresh concrete before the concrete dries and has a chance to create its own joints, which we call cracks.
What is the best concrete expansion joint material?
Why Silicone is the Best Expansion Joint Filler Silicone provides an excellent alternative to the three expansion joint fillers above, and for a few reasons.
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. By contrast, an expansion joint (or movement joint) is sized and formed at a width prescribed by the building design team and sealed and bridged later by an expansion joint system.
What is the black stuff between concrete slabs?
An expansion joint is a material placed in the cracks (or joints) between concrete slabs to protect the slabs from cracking when they contract and expand as the temperature changes. This material acts as a shock absorber, absorbing the stress from the slab’s movement.
What is the distance between expansion joints?
Expansion joint spacing is dictated by the amount of movement that can be tolerated, plus the allowable stresses and/or capacity of the members. As with contraction joints, rules of thumb have been developed (Table 3). These range from 30 to 400 ft (9 to 122 m) depending on the type of structure.
Where are expansion joints required?
Expansion joints occur through all parts of a structure to provide complete separation – through floors, walls, ceilings, and roofs (interior & exterior).
Do I need to fill expansion joints?
It might sound like a good idea, but if the joints are filled with a solid material and then covered with epoxy, it defeats their purpose. Improperly filled expansion joints is where the chips and cracks in floors are born. We do not fill the expansion joints; we paint epoxy over them to get the color continuity.
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.
Where do you put expansion joints in concrete?
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.
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.
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.
How many times do you float concrete?
For a really smooth finish, repeat the troweling step two or three times, letting the concrete harden a bit between each pass. At first, hold the trowel almost flat, elevating the leading edge just enough to avoid gouging the surface.
Do you push or pull a concrete saw?
Always let the saw do the work; simply guide its direction, but don’t push it down into the concrete. You only need a quarter-inch cut at this point, but if the saw bites in a bit deeper, that’s fine too. This first guided cut will ensure you keep your cuts straight during the rest of the project.
How much do expansion joints cost?
The price to repair expansion joints and control joints greatly depends on how bad the damage is. Preventative joint filling can cost between $1.50 and $3 per lineal foot, but once expansion joint repair or control joint repair is required, the costs can vary from $15 – $100 per lineal foot of joints.
