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What is the Tongue and Groove Joint (Why Do We Use It?)

A look at two pieces of wood with tongue and groove joint.

Learn more about the wood joinery technique of tongue and groove joint, where it is best used, how to make it, its adavantages and what equipment you need to achieve it.

There is something inherently special about going into an antique store and observing the detailed craftsmanship of the wooden furniture. Hinges with ornate designs, initials carved into corners,… the care and attention put into these pieces are obvious and make for a meaningful and timeless item. Unfortunately, certain methods of woodworking become obsolete over time as more convenient and less time-consuming methods are innovated.

The classic wood joinery technique of the tongue and groove joint is just one example of this loss. Although not entirely forgotten, this sleek and satisfying way is harder and harder to come by.

Related: Mortise and Tenon Joint | Rabbet Joint | Dowel Joint | Dovetail Joint | Miter Joint | Dado Joint | Butt Joint | Lap Joints

What is a Tongue and Groove Joint?

The tongue and groove joint is the wood joinery method of fitting panels of wood together by their edges. This is done by conjoining the two pieces with a groove and a tongue! There are two types of tongue and groove joints: The Solid Tongue Joint or The Slip Tongue Joint.

The Solid Tongue Joint

The groove is a deep ridge cut along the entire edge (usually in the shape of an open-ended teardrop). The tongue is on the opposite edge and is of the appropriate shape to fit like a puzzle piece into the groove.

The tongue is made to be slightly smaller than the area of the groove, to aid in smoother assembly. They are put together by sliding them down the edge to edge, starting at the tips of each panel. Then the glue is added to the joint, and the tongue slightly absorbs some of the moisture and expands into the groove to make for a wonderfully snug fit.

The Slip Tongue Joint

This is entirely similar to the solid tongue joint, with the only difference being that each panel of wood has a groove put into their edges, and a third party spline is created to join them together. A splice is a wafer of wood that is cut to the perfect size to fit into the correlated grooves.

The solid tongue joint gives you the option of not glueing the pieces together to finish (when fabricating a table designed to have removable slats), but the slop tongue joint must be glued for the panels to stay together.

A wooden flooring with tongue and groove joint.

When is a Tongue and Groove Joint Used?

The principle place where the joint can be found is with wood flooring. Once the introduction of plywood and composite wood boards were innovated, tongue and groove joints became very rare methods for flooring. This type of woodworking is pricey and time-consuming, whereas plywood is inexpensive and makes for incredibly easy assembly.

The tongue and groove joint can still be found in the fabrication of high-quality table making and cabinetry.

And don’t forget about parquetry! This is woodworking purely for aesthetically pleasing purposes. Parquetry is the art of geometrically placed mosaics of dyed wood.

Why the Tongue and Groove Joint?

The tongue and groove joint is basically just a mortise and tenon joints, but really really long. The reason for them having different names is to describe their differences in appearance and overall nature. The mortise and tenon joint is to introduce rigidity and strength to wood joinery and are connected at right angles. Whereas the tongue and groove joint is joined in parallel wood pieces (thus the need for a longer area for joining).

This joint is typically stronger than a butt joint, as the tongue and groove joint relies on surface tension which extends throughout the entire panel of wood. The butt joint uses external hardware to hold the joint together, which ends up causing stress on specific areas.

A man installing wood paneling onto the ceiling.

What is Needed?

The most common supplies needed to make your very own tongue and groove joint are:

  • wood shaper (spindle moulder or router – used for trimming and shaping pieces of wood using a rotary mechanism
  • circular saw bench 
  • hand plane

There are several places that instruct you on how to create your own tongue and groove joint, here are some reliable options:

FAQ

What are the types of tongue and groove joints?

The two types are the slip tongue joint, and the solid tongue joint. The slip tongue has grooves of the same size that are connected by a third party spline that is then glued into place. The solid tongue joint has a groove on one edge, and a tongue on the other edge that fit together like puzzle pieces. Glue can also be used with the solid tongue joint as reinforcement.

How is a tongue and groove joint made?

These can be made by hand whittling (welcome to 1832) or a circular saw, spindle moulder or router. Just scroll up to find instructional videos and articles on how to achieve a groove joint.

How strong is a tongue and groove joint?

They are very strong! When the joint is reinforced throughout the entire surface area of the piece of wood, its strength will always be greater than if third party hardware is introduced.

Why aren’t tongue and groove joints popular?

They have been replaced with cheaper and less time-consuming panel joinery methods like plywood sheets. Tongue and groove joints take time, and when you’re planning on covering them with an entire floor, that is a lot of grooves and tongues to create. Time is money and money is time!

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