Diagram of a common rafter timber frame. Shows walls, aisles, common rafters and plates.

Timber Frame Anatomy – Common Rafter system

Diagram of a common rafter timber frame. Shows walls, aisles, common rafters and plates.
Common Rafter Frame

The Common Rafter system

The second in a series of articles exploring some common types of timber frame configurations. The common rafter and long plate system in timber framing is consider by many to be the traditional style of American timber framing. Roof joinery is a little more involved than with the principal rafter and common purlin system. Assembled and raised as wall-lines this configuration lends itself to a hand raising.

Advantages

  • Most of the timbers have smaller section which are easier to cut with -"standard" power tools.
  • Platform nature of the assembly lends itself to a hand raising
  • Preferred by people who want the appearance of lots of timber

Disadvantages

  • More timbers
  • Joinery is slightly more involved
  • Long timbers might be hard to source for large structures

Parts of the Frame

In this simple frame there are three wall-lines, that form two aisles. Plates connect the corner posts along the exterior wall-lines. Ties/Girts connect the exterior wall-lines with the interior wall-line.

Frame parts
  1. Wall-line – a longitudinal sectional assembly of timbers that are parallel to the ridge.
  2. Aisle – the area between the two wall-lines.
Timbers List
  1. Corner post – Main posts that connect to plates.
  2. King post – Central post that leads to the ridge.
  3. Common Rafter – Repetitive angled roof timbers.
  4. Girts/Ties – Horizontal beam that ties the outer posts with the interior king post. Located along exterior walls means they are also girts.
  5. Plates – Horizontal timber that support rafters.
  6. Brace – Angles scantlings that provide rigidity to the frame.
Timber frame with common rafters
Timber frame with common rafters