Whats the difference between a Bent and Bay System and a Post and Beam System?
The term Bent and Bay System has remained primarily the same in the industry since the beginning of Timber Framing. This refers to a construction process where individual bents are created and raised into place. (Refer to diagram A) The space between the Bents is referred to as Bays. This style was created for ease of manual erection of a frame. Each Bent can be assembled on the ground and raised into place by man, horse power, or modern day crane; then connected together with Plates and Girts.
The term Post and Beam has changed in time and has several
different meanings; this depends on who you are receiving your information
from. Log Home Outfitters considers Post and Beam a style of Timber Framing
where the tradition Bent and Bay System is not used. (Refer to diagram B). The
traditional Joinery methods are still used, but the traditional layout method
of the Bent and Bay system is abandoned lending to a more of free-form style of
Mortise: Most commonly used joinery in Timber Frame construction. The mortise is the notching into a post or truss plate to receive the tenon. Used in conjunction with a tenon, this joint resists both gravity and lateral loads.
Tenon: The tenon is used in conjunction with the Mortise. The tenon is the removal of end material of a post,
plate, brace, or girt to fit into a mortise joint.
Housing: Creating a secondary edge on a Tenon or Dovetail to increase the gravity load capabilities of a joint. Housing, can be fully concealed or exposed depending on the design preferences of the owner.
Dovetail: Dovetail joints are strictly used at gravity load conditions; such as Rafters, Purlins, and Joists. The ends of the Rafters, Purlins, and Joists are shaped to slide into a pre-cut slot within the plate. The connection has a back cut to resist pulling out of the plate.
are used as the primary element to resist lateral loads in a Timber Frame.
Braces are used at the horizontal to vertical member transitions of a Timber
Scarf Joint: A scarf joint is used when a horizontal member, primarily a plate, is so long that two or more individual members are required to meet the length requirements. In timber frame joinery the most structurally sound connection when two plates need to be joined is to connect the plates beyond the post instead of on the post.
Shoulder Joint: Shoulder joints are used where a Top Plate and Bottom Plate of a truss meet to help resisting the outward thrust created on an angled connection created by roof loads. The Bottom Plate of the truss is notched to receive the notched end of the Top Plate.
are used where more then 3 members are coming into a single connection point. 2
horizontal members can use the standard mortise and tenon joint into a post.
The other 2 members have a simple house connection on the ends onto the post to
take care of the gravity loads. A Spline is cut thru the post and into the top
or bottom of the other 2 horizontal members and those members are pegged to the
Spline to resist the pulling out forces
on the connection.
Chamfer: A Chamfer is a beveled edge of a Member. A Chamfer was originally uses at the end of Tenons to help in the fitting into a Mortise. In today's Timber Frames it is used as a decorative element on the timber framing pieces.
Post: Vertical members in a Timber Frame.
Plate: Primary horizontal members used in a Timber Frame, found at the Floor, Roof Framing Planes, and Top and Bottom members of a truss. Used as a connection between Posts, Bents, and Trusses to receive Joists, Rafters, or Purlins.
Girt: Secondary horizontal members used in a Timber Frame, found between the Floor and Roof
Framing Plates. Used as a connection point for exterior veneer, or window and door headers.
Purlins: Framing elements between plates of a truss for roof veneer connections.
Rafters: Framing elements running parallel with plates of a truss connecting Ridge Plate of a Roof and Eave Plate. Used a connection point for roof veneer.
Joists: Horizontal framing elements between plates at floor line for floor supports.
Gravity Load:Vertical loads created by weight of Timber Frame members and loading of floor or roof system. Includes Snow Loads.
Lateral Load:Horizontal or angled loads created by angled roofs, wind, or seismic loads.