
If your roof is going to be either a hip roof or a valley roof, then you will need to include jack rafters in the design, as they comprise most of the shorter lengths of rafter used to make up the construction of the roof. Jack rafters are generally made from wood. They essentially perform the function of an infill piece rather than forming one of the main lengths of timber used in the construction process.
Obviously if you have jack rafters then you are likely to have a conservatory that is completely made from hardwood. This can look stunning, and it has the advantage that your conservatory will be distinctive by its exposed beams and wooden surfaces. This can make the conservatory look older than it actually is, and give it a classic good look.
Jack rafters form part of a more complex roof design. If you are intent on building your conservatory yourself then you will need to have an in depth knowledge not only of roof building, but of the angles required to cut the jack rafters and the other timber to the correct length.
If you want a conservatory that looks rather more solid than the more common uPVC appearance, then using a solid wooden structure complete with jack rafters inserted into the roof design will no doubt meet your needs.