Purlins help to form and strengthen the roof framing in a structure, and they support the roof decking or sheathing. They run horizontally, parallel with the ridge of the timber frame. There are three basic types of purlins: Purlin plate, principal purlin, and common purlin.
Timber Frame Construction Details
Cross lap joints are a great solution when you want to create clean, continuous lines in a timber frame. The edges of the joint are completely flush, making it almost appear that the timbers are magically connected. To create a cross lap joint, you cut halfway through the width of both timbers that you are connecting , and they slide together into an extremely solid joint.