Types of Joints in Construction

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  Most fundamentally, construction is the act of joining different materials together. A wide variety of different ways to do this exist. For instance, to construct smaller items, such as furniture, several types of wood joints are used, which usually involve cutting the two sides of the joint to dovetail with one another. To build larger structures from wood, the parts of the joint are secured with nails. Concrete is also used in construction which involves three main styles of joints. These joints come into play during the course of a construction project.
  
  

Small-scale Construction Wood Joints

• For smaller construction projects, these are some of the most popular joints:
  
  Biscuit joints are made with oval-shaped pieces of composite wood that are inserted into specialized grooves cut into each side of the joint.
  
  Dovetail joints consist of two joints whose sides are cut into a series of small trapezoidal shapes, which are then fitted together.
  
  Box joints are similar in concept to dovetail joints, but in this case the two sides of the joint are cut into very basic square shapes and then joined together.
  
  Dado joints are often used to make bookshelves. They consist of a groove cut into one side of the joint into which the other side fits snugly. Sometimes the side that fits into the other is cut so that a long lip protrudes from the piece which fits into the other side of the joint.
  
  Domino joints are two small, domino-shaped pieces of wood that fit into holes cut in each side of the joint. These joints are similar in concept to biscuit joints.
  
  

Building Construction Wood Joints

• For constructing buildings and other structures, three types of joints are primarily used:
  
  Barefoot joints consist of one piece of lumber resting upon another at a perpendicular angle. A nail is inserted at an angle to connect the two pieces together.
  
  Oblique butt joints are necessary when a piece of wood must run at an angle. The angle is cut into one side of the piece and rests upon the other board at the appropriate angle. Nails are then used to connect the two pieces together.
  
  Mortise and tenon joints provide a stronger bond between the two pieces of wood. A rectangular hole is cut into one side of the joint, and a rectangular protrusion of equal measurement is cut into the other side. The two sides are then joined together.
  
  

Concrete Construction Joints

• Concrete construction involves three major types of joints:
  
  Contraction joints are used to avoid cracking from concrete shrinkage. They consist of two sides with mated, waved cuts at a right angle to the ground with a dowel or metal rod connecting them.
  
  Construction joints are used to join two masses of concrete poured at different times. They are usually cut in a straight line or have a single protrusion for stability, with a bar between them.
  
  Isolation joints connect concrete to a building or structure to allow for any building shifts without affecting the concrete. They consist of a gap between the two slabs with filler inside of it.