Double Bobtail Truss
A plated timber double bobtail (double stub) truss: two rafters meeting at the apex, a ceiling tie, a vertical post at each end that carries the rafter at the stated end height, a diagonal from each post foot to its rafter and a W of webs between the rafters and the tie, drawn as members without connector plates. Span, pitch and overhang, End height, the vertical at each end, Member thickness and chord and web depths
Details
Category: Roof Framing › Timber Roof Framing › Straight Truss Roofs › Timber Trusses
By Huu Khanh Nguyen · Updated November 4, 2026
Parameters
| Name | Default | Unit |
|---|---|---|
| Span | 8000 | mm |
| Pitch | 35 | ° |
| Overhang | 450 | mm |
| Member Thickness | 35 | mm |
| Chord Depth | 97 | mm |
| Web Depth | 70 | mm |
| Slope | Math.tan((pitch * Math.PI / 180)) | |
| Heel Height | chordDepth / Math.cos((pitch * Math.PI / 180)) | mm |
| End Height | Math.max(Math.max(chordDepth + heelHeight + 2 * webDepth, 600 - span / 2 * slope, span / 6.67 - span / 2 * slope), Math.min(span * 0.113, span / 2 * slope)) | mm |
| Rafter Node Fraction | 0.184 | |
| Tie Node Fraction | 0.286 | |
| Width | span + 2 * overhang | mm |
| Depth | chordThickness | mm |
| Height | endHeight + span / 2 * slope - Math.min(0, endHeight - heelHeight - overhang * slope) | mm |