Tuesday, May 26, 2009

Types of Timber Framing

There are two general types of timber frame systems, each having several variations: Common Purlin systems consisting of King Post, Queens Post (see modified Queen Post Truss below), and Hammer Beam frames for example, and Common Rafter systems such as Collar Tie, Principal Purlin, and Ridge Beam frames. There are many reasons to choose one frame type over the other and costs vary as well.

Common Purlin systems, or timber frame bents, are typically assembled on the first floor deck, then raised as whole units into place by a crane (see photos bottom), connected with the joinery, and secured with wooden pegs. Because of the structural integrity of these bents, this system of timber framing allows for an open, flexible floor plan.

Common Rafter systems are raised either as ‘walls’, one timber at a time. Timbers are erected in succession; one end post erected first, then a connecting beam at the second floor level is secured to the post, then another end timber is joined to the beam. Timber ends are fastened with some form of mortise & tenon joinery. Joints are typically fastened with pegs, which can be cut flush to the joinery or left protruding for decoration.

If you already have a timber frame design in mind, most likely the design will dictate which kind of timber frame will be used according to spans and interior walls; however if you would like to incorporate a specific timber frame (or a combination of timber frames) into your home design, your timber frame architect can design the home around the timber frame.

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