There are ways to build a truss for your house or deck, even a bridge if you are so inclined. But to do it the right way one must adhere to some pretty old and pretty strict rules of construction.
First a definition. A wooden truss is a very strong and stable frame made of wood and held together with metal connector plates. It is of an ancient design. A truss adds support and shape to a roof, bridge et al. Some others describe it as an open web type of design that is appropriate for supporting roofs, decks, or floors.
A wooden truss can be constructed by a carpenter but most are designed buy a contractor or an architect and are kept to very strict standards. Important items to remember are; peak of the truss, pitch, clear span and overall length, and overhang. Also some of the types of wooden trusses include the step-down hip, the cove, and the Polynesian.
Some of the items needed to construct your own truss include; Lumber-make sure it is not too moist. There are strict regulations on the moistness of lumber. Make sure the lumber is flame retardant according to specs. Metal plate connectors-these must be connectors that are rust free and meet certain steel specifications for thickness and ability to resist corrosion.
And because of the preceding two paragraphs it is recommended that a do-it-yourself project should be a pre-fabricated truss made by a reputable manufacturer of which there are legion. Costs vary but wooden trusses are less expensive than those made of other materials.
Once a pre-fab truss is purchased there are instructions included that must be followed very closely. Accuracy is the word here. They come with a list of tools needed and recommendations also.
If the truss is sizable, and they usually are, special hoisting lifts help put them in place. That will be the toughest part of putting together a pre-fab truss. Once in place follow directions on how to fasten and what angles and degree of pitch should be used. It is best done by more than two people.
As always safety is an issue that must be considered. After it is in place and the metal connectors are in the whole affair should be inspected by a certified contractor. There is a multitude of designs and other connectors but the metal connectors are the key to a safe and stable wooden truss. It costs money but installing a big truss for do-it-yourself jobs is a daunting task.
But it can be done. And of course smaller trusses are much easier to install. Sometimes it makes sense to attempt to install a small less complicated truss as practice before tackling a major size wooden truss.
As stated before the truss also shapes the roof or deck or floor, so keep this in mind when choosing a design.
Sometimes it is wise to consider using a metal truss. This would be expedient in moist environments where the metal can be dipped or treated to last much longer without suffering from corrosion. But metal trusses are less user friendly, and more expensive.