Tongue and Groove

Tongue and Groove

An edge joint that involves one board to have a groove and the matching one to have a ridge or “tongue” that interlocks with the groove is the basic mechanics of a tongue and groove joint. Presto! The tongue goes into the groove and the boards are joined!

Similar to the other well-known dovetail joint, the tongue and groove joint allows two flat pieces to be joints strongly together to make a single flat surface. We see this a lot in today’s flooring, many of which now snap together the wooden floorboard pieces using tongue and groove joinery. It’s also commonly used in expensive cabinet- work, where dovetail and multiple tongue and groove are used.

In furniture making, the tongue and groove is excellent for edge-to-edge glue-ups and angles. The precise design allows adjoining boards to come flush while constructing and gluing.  As well the effect of wood shrinkage is concealed when the joint is beaded or otherwise molded.

The key to this joint are the proportions. Good proportions are essential to produce a strong joint. A joint that is too tight or to loose is detrimental. Even if a tongue is slightly too fat but still sits in the groove it can give stress to the groove’s sidewalls and in time may split the wood. So precision is necessary. Gives more weight to the measure twice, cut once mantra!

Historically the tongue and groove joint was also used for aligning vertical paneling in early homes (which allowed the joint to adhere to seasonal expansion & shrinkage while also creating an airtight wall). It became more popular once strip hardwood flooring came into being around 1885 and modern machine made tongue and groove hardwood flooring was created.

In the end there are a lot of uses for this little joint and its popularity isn’t going anywhere any time soon. Where do you see a tongue and groove joint in your home? We bet you’ll start seeing them everywhere you go now!