3 Types of Concrete Construction Joints

What are the Different Types of Concrete Construction Joints?

There are three different types of concrete construction joints: Butt-Type, Keyway, & Dowel.

Why are Concrete Construction Joints Necessary?

Whether we like it or not, dirt moves. In turn, concrete slabs are going to move. Concrete construction joints are what keep the two slabs from shifting between one another. In other words, the construction joint keeps the concrete from shifting up and creating a tripping hazard.

#1 Butt-Type Construction Joint

The Butt-Type construction joint is very simple. One concrete slab is poured directly up to another concrete slab and the connection at the top of the two slabs is edged for aesthetics. Butt-Type joints are only applied where light vehicle and foot traffic are the heaviest loads on the slab.

#2 Keyway Construction Joint

The keyway construction joint is probably the most complex construction joint. This joint requires the time to build or buy a wooden, plastic, or metallic keyway and install the material into your formwork. The keyway will act as the slab edge for the pour. When forces push one slab vertically from the other, the keyway construction joint will hold the two slabs together. Keyways are typically applied in commercial settings.

#3 Dowel Construction Joint

The dowel construction joint is no different than the butt-type, except it has smooth dowels connecting the two slabs at approximately eighteen inches on center. In the case that the subgrade pushes one slab vertically, the smooth dowel will hold the two slabs together, while still allowing the slabs to expand and contract independently. The dowel construction joint is often used in commercial slab settings where heavy equipment such as forklifts will be regularly crossing the joint.