Expansion Joints in Concrete Slabs of Driveway: Best Practices
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Where Should Expansion Joints in Concrete Slabs of Driveway be Placed?
Expansion Joints in concrete slabs of the driveway should be placed wherever the new slab abuts an existing slab or any other rigid obstruction. A long concrete driveway is often poured in sections and expansion joints are used to isolate one section from another.
Expansion Joints in concrete slabs are often confused with Control Joints. They have similarities but they are not the same.
Control Joints (aka Contraction Joints) should be 2 – 3 times (in feet) of the concrete thickness (in inches) apart from each other.
For example, Control Joints should be 8’ – 12’ apart in a 4” thick concrete driveway and 12’ – 18’ apart in a 6” thick concrete driveway.
Control Joint Vs Expansion Joint: What Is the Difference?
Concrete develops shrinkage cracks as it cures. The purpose of Contraction Joints (aka Control Joints) is to encourage shrinkage cracks to stay within the joint. The appearance and spread of shrinkage cracks is controlled to a degree.
Expansion Joints in concrete slabs serve a somewhat different objective. Expansion Joints (aka Isolation Joints) separates one concrete slab from another or from a rigid object such as a lamp post or drain pipe.
Expansion Joints give space for a concrete slab to expand, when temperatures go up, without pushing on the adjoining slab, foundation or any other rigid obstruction.
Where Do Expansion Joints Go in a Concrete Driveway?
Expansion joints in the concrete driveway are required in following situations:
Driveway Edge with Apron
A concrete driveway is sure to have a concrete apron where the driveway transitions into the street. The concrete apron is a separate slab usually thicker than the concrete driveway.
An expansion joint should be placed where the concrete driveway meets the concrete apron.
Concrete driveways lead up to the garage. A garage apron is installed at the garage door as a transition between the driveway and the garage floor which are two different slabs.
An expansion joint should be placed where the driveway meets the garage apron and the garage apron meets the garage floor.
Driveway Edge with House Foundation
More often than not the main driveway or a branch will lead to the front porch of the house. The concrete slab of the driveway will be in contact with the house foundation.
The two structures must be isolated from one another by installing an expansion joint.
Rigid Obstruction
You may install lamp posts, concrete planters or drain pipes along the driveway. These objects should have their own slabs or foundations. Moreover, they should be kept separate from the concrete driveway slab so that thermal expansion can take place freel without any stress.
Expansion joints are required to isolate the concrete driveway slab from any rigid obstructions.
Isolating Sections of a Driveway
When installing a long driveway it is better to pour it in smaller, more manageable sections.
Concrete begins to cure and set immediately after water is added to the cement-aggregate mix. The window to pour, screed and finish a section is short. Pouring a driveway in sections reduces risk of ending up with unworkable concrete.
However, this also requires that each section be poured & finished separately and the sections isolated from each other by an expansion joint.
Should You Caulk Expansion Joints in Concrete Driveway?
It is absolutely essential that you caulk expansion joints in a concrete driveway using a flexible, self-leveling, waterproof silicone caulk.
The expansion joint is as deep as the concrete slab thickness and usually ¾ “ wide. Unless it is caulked, water will fill up in the joint and penetrate into the concrete substrate.
The caulk has to be both waterproof (to prevent water ingress) and flexible ( to permit thermal expansion). The caulking should fill up the entire expansion joint but be just slightly below the driveway surface. This will prevent it from wear & tear from vehicular traffic.
Backer rod can be inserted in the expansion joint to reduce the consumption of the expensive caulk.
Once you have caulked the expansion joints in concrete slabs of your driveway, you must seal the entire driveway surface with a high quality topical sealer.
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Thank you very much for reading this post. I do hope you found it informative and helpful.
