There comes a time when a roof will need replacing, repairing or modifying. In these days of prefabricated trusses it's not every carpenter that can build a cut roof, but few jobs are more satisfying to a skilled carpenter than creating this solid structure from individual lengths of timber.
Some roofs are more complex than others. Four hips, two valleys and a gable end had to be incorporated into this roof and as it was for a conservatory everything was on show, leaving no room for error.
The king post truss is one traditional method of supporting roofs over a large span. The trusses support purlins on which are sat the rafters. The trusses shown are made from green oak and were incorporated into a barn conversion.
The trusses are constructed using mortice and tennon and bridle joints, the only mechanical fixing being a bolt inserted through the tie beam and into the king post, the end of the bolt being accessible via a slot cut into the king post.
This series of photographs shows an oak king post truss under construction, in this image half of a bridle joint has been formed in the tie beam, into this will sit the corresponding half which will be formed at the lower end of the princpal rafter.
Here the two section of the bridle joint have been formed and the principal rafter and tie beam are ready to go together.
The king post is located in the centre of the tie beam and joined to it with a stop mortice and tennon joint.
The tops of the principal rafters are joined to the king post using stop mortice and tennon joints. A notch is cut in the top of the king post into which the ridge board sits.
The finished article waiting to be lifted into position.
This douglas fir roof truss was bolted together as specified by a structural engineer.
The timbers are held together with steel plates and the purlins are in position.
