Wood Connections There are basically five different types of connectors: Interlocking (carpentry joints), Dowel, Metal Connectors, Special Formed Connectors and Adhesives. I Interlocking (Carpentry Joints)

• Mortise and Tenon The most common traditional timber joint, the mortise is a slot made into a member that receives the tenon, a projecting tongue of wood on the end of the connecting member. Pegs, small dowels inserted into holes that pass through the mortise and tenon of each member, act to prevent movement at the joint. This type of joint creates only a ‘post and beam’ type of connection; no resistance to rotation and hence stability is provided. There are many variations of the basic mortise and tenon joint.

Wedged dovetail tenon Stub tenon joint Bridle scarf and side-halved scarf

• Butt Two pieces of wood meeting with flat sides adjoining usually at right angles. Some type of connector is needed to prevent movement.

Butt joint with dowels Butt joint with ‘biscuit’ Butt joint with screws or nails

• Miter or mitre Two pieces of wood meeting at right angles with each piece cut at 45º.

• Lap A very common type of joint in which a portion of each connecting member is removed in order to create a flush interlocking connection. Some type of connector (dowel, glue, screw, etc.) is required to prevent movement.

Halving joint

• Finger A strong joint that creates a flush connection. II Dowel

• Staples Useful to fix thin panels or other materials to a wood frame.

• Nails Most widely used dowel-type fastener. Many types of nails of different sizes, shapes and materials (steel, galvanized, etc.). Each nail has a specific strength in shear. The number of nails required depends on the total shear transfer between the connected members. A smooth or shank profile nail is the most basic. Nails with annular rings are called threaded nails and have improved withdrawal strength.

• Screws Larger and with greater strength than nails. Used in smaller number than nails. Can be used to connect wood to wood or metal to wood. Most common types are: countersunk head screw, round head screw and coach screw.

Coach screw (countersunk) Wood screw (countersunk)

• Bolts Threaded dowel-type fasteners designed to be fitted with a nut to prevent pullout. Strongest of dowel-type fasteners and larger in cross section. Common types are: hexagonal head bolt, square head bolt and carriage bolt.

Hexagonal head bolt Carriage bolt

• Dowels Plain, circular rods that are fitted snuggly into drilled holes. They transfer load entirely by shear.

III Metal Connectors

• Metal plates 2D Metal plates are typically flat plates that lap across two pieces of wood to be connected and rely on the shear resistance of both the metal plate and the nails that penetrate into the wood members. Plates can have holes into which are driven nails, or they may be formed in which case the nail is incorporated as part of the metal plate. These are often referred to as nailing plates.

Metal plate with holes Punched metal plate fastener with teeth

• Metal Plates 3D Three-dimensional metal plates are formed to facilitate connections between wood members. Common types are: joist hangers, truss clips and brace anchors. These are provided by various manufacturers.

Joist hanger Truss clip Anchorage for brace

• Connectors with bolts Metal conectors with bolts are usually hidden within the wood member. There are three types: split-ring, shear-plate and toothed-plate.

Split-ring connector

Shear-plate connector Toothed-plate connector

• Metal Gusset Plates Mainly used for connecting multiple members together in a truss, Can have a wide variety of shapes to fit the geometry of the joint. Can be bolted or screwed.

IV Special Formed Connectors

• Nodal connector Nodal connectors are specially designed metal components that conform to the geometry of the desired connection. They can be fabricated from plate steel or alternatively, formed from casting.

A complex nodal connector of interlocking steel plates A pin-type connector of welded plate

Cast steel pin-type connector

V Adhesives

• Adhesively bonded connections All engineered lumber products use adhesives for the manufacture of panels (plywood, particle board, strand board, etc.), laminated lumber (glulam, LVL, PSL, LSL, etc.) and for special sectional components: timber I-joists, box beams and stressed skin panels.

• Resin-anchored bolts Adhesives applied to a bolted connection to improve the performance of the overall connection.

• Glued gusset plates Plywood gusset plates can be connected with adhesive replacing nails.