A king post truss has a single vertical post from the ridge down to the centre of the bottom chord — the simplest truss there is. Typical span: commonly up to about 26 ft. Truss count comes from the building length rather than the span — divide the length by the spacing, add one, then add two gable-end trusses.
A king post truss has a single vertical post from the ridge down to the centre of the bottom chord — the simplest truss there is. This page gives the truss count at 24 and 16 inch centres, the rafter length and the ridge height for the spans a king post truss is normally used at, along with what distinguishes it from a standard fink truss, where it fits, and the constraint that decides whether it will work on your building. Typical span: commonly up to about 26 ft.
| Span | 4/12 rafter | 6/12 rafter | 8/12 rafter | 6/12 ridge height |
|---|---|---|---|---|
| 16 ft | 8.4 ft | 8.9 ft | 9.6 ft | 4 ft |
| 20 ft | 10.5 ft | 11.2 ft | 12 ft | 5 ft |
| 24 ft | 12.6 ft | 13.4 ft | 14.4 ft | 6 ft |
| 28 ft | 14.8 ft | 15.7 ft | 16.8 ft | 7 ft |
| 32 ft | 16.9 ft | 17.9 ft | 19.2 ft | 8 ft |
| 40 ft | 21.1 ft | 22.4 ft | 24 ft | 10 ft |
A king post truss changes the webbing inside the outline, not the outline itself, so the rafter length and ridge height are the same as any other truss at that span and pitch.
Truss count comes from the building length, not the span. Divide the length by the spacing, add one for the final end, then add the two gable-end trusses.
| Building length | At 24 in centres | At 16 in centres |
|---|---|---|
| 24 ft | 15 | 21 |
| 32 ft | 19 | 27 |
| 40 ft | 23 | 33 |
| 48 ft | 27 | 39 |
| 60 ft | 33 | 48 |
Counts include the two gable-end trusses, which are a separate component from the commons and are ordered as such.
| Typical span | Commonly up to about 26 ft |
|---|---|
| Best for | Short spans: garages, porches, small outbuildings and open-frame feature roofs |
| Watch for | Span is limited — beyond about 26 ft a queen post or a fink carries the load more efficiently |
A king post truss has a single vertical post from the ridge down to the centre of the bottom chord — the simplest truss there is.
Commonly up to about 26 ft. The exact limit depends on the timber species and grade, the spacing, and the snow and wind loads for your area, so the truss designer sets it rather than a table.
Divide the building length in inches by the spacing and add one, then add two gable-end trusses. A 40 foot building at 24 inch centres needs 21 common trusses plus two gable ends.
No. Cutting, notching or drilling any truss voids its engineered design. If it does not fit, the answer is a redesign from the truss plant, not a saw.