Traditional joinery is a term we’ve all heard as a hallmark of historical millwork. But what is it and why is it so important in preservation of historic buildings?
What is Traditional Joinery?
Joinery in general is the woodworking technique that joins together two pieces of wood. What a joint looks like, how strong it is, how long it will last, and other characteristics are all determined by the joining materials and how they are used in the joints. Traditional joinery techniques use only wood elements, while modern joinery techniques use fasteners, bindings, and/or adhesives. Sometimes the two techniques are combined to marry wooden elements and joints with modern adhesives.
Traditional joinery uses the following joints:
Butt joint: The end of a piece of wood is butted against another piece of wood. This is the simplest, and weakest, joint in traditional joinery.
Miter joint: Similar to a butt joint, but both pieces have been beveled (usually at a 45 degree angle) before being joined together.
Lap joints: One piece of wood overlaps another.
Box joint (or finger joint): Several lap joints at the ends of two boards; used for the corners of boxes.
Dovetail joint: A form of box joint where the fingers are locked together by diagonal cuts.
Dado joint: A slot is cut across the grain in one piece for another piece to set into; shelves on a bookshelf having slots cut into the sides of the shelf, for example.
Groove joint: The slot is cut with the grain.
Tongue and groove: Each piece has a groove cut all along one edge, and a thin, deep ridge (the tongue) on the opposite edge. If the tongue is unattached, it is considered a spline joint.
Mortise and tenon: A stub (the tenon) will fit tightly into a hole cut for it (the mortise). This is a hallmark of Mission Style furniture, and also the traditional method of jointing frame and panel members in doors, windows, and cabinets.
Birdsmouth joint: A V-shaped cut in the rafter connecting roof rafters to the wall-plate.
Comb Joint: A joint used as a way of conserving timber, as a means of joining random lengths of timber to be machined to a finished piece.
Source for pictures and joint descriptions: Wikipedia’s Entry on Traditional Woodworking Joints
Why it’s Important in Preservation
There are many advantages to using traditional joinery in the preservation or restoration of a historic building. Using traditional joinery in repairs, restorations, and other preservation ensures the structural integrity of a historic building by matching existing joinery with a joinery technique that’s sure to be compatible with it. Since traditional joinery is stronger, more durable, and expands and contracts in different ways than modern joinery – using modern joinery alongside traditional joinery can compromise the structure of a historic building.
Traditional joinery is a time-tested method that is much stronger than modern joinery and lasts for generations, even thousands of years. The mortise and tenon joint is the most ancient traditional joint and has been found in the wooden planks of a vessel 43.6 meters long that dates to 2,500 BCE. Traditional Chinese architecture as old as Chinese civilization itself used this method for a perfect fit without using fasteners and glues. The 30 stones of Stonehenge were also fashioned with mortise and tenon joints before they were erected between 2600 and 2400 BCE.
Proving itself to be able to stand the test of thousands of years, traditional joinery is clearly a higher quality and more stable joinery method than modern techniques. That test of thousands of years also demonstrates traditional joinery’s ability to withstand the rigorous use we often demand of our structures joints because it is a higher quality, more stable joinery method than modern techniques.
One of the reasons traditional joinery like mortise and tenon joints withstands the test of time so well is that it allows a joint to naturally expand and contract with moisture and temperature changes in the environment without devastating separation that weakens the joint and causes (often irreparable) damage to the wood pieces it’s joining together.
But most importantly, traditional joinery ensures authenticity in the preservation of our built history by more completely matching the existing materials and construction methods used by traditional trades. Since the traditional trade methods that originally constructed a building (along with regional variances in those methods) are a large contributor to a building’s historic fabric, this is the best way to make sure that historic fabric is not lost to our preservation efforts. Traditional joinery also better allows for selective repair or reconstruction of individual components than modern joinery methods – a major advantage that helps preservationists retain more of the woodwork original to a historic building.