Standard trusses may span up to 11 meters in 35mm wood and 15 meters in 47mm wood. Spans greater than this can be created, but are often supplied as many trusses joined together. The weight of the roof is divided between the trusses. The type of wood used to make a truss has little effect on its strength. However, heavier wood is usually more stable when drying out which is important when making large-scale structures. Redwood and maple are commonly used because they are heavy and strong. Other options include sycamore, hickory, and fruit trees leaves and branches. It's also possible to use metal for the main beams of a truss-based structure. These would be the main supports under the roof with trusses attached only at their ends. They would need to be very thick to be able to take the weight of the roof. The size of the timber used to build a truss depends on how long it is expected to last. A standard truss should be built from wood that is 45-60 mm thick. This gives it enough strength to carry its own weight and those of any additional roofs it might have. Larger or smaller trusses can be made by using thicker or thinner wood, respectively. Most truss manufacturers will tell you what size timber they use when they quote prices for their products.