Trusses or Conventional "Stick" Framing.
What's the Difference? cont.

By Bob Linnert, Better By Design LLC

Trusses are engineered roof components that are designed by a truss designer (that used to be me) using computer software that engineers each truss for its specific location within the roof system. A simple rectangular house with a gable roof may only have one truss type repeated multiple times (usually at 2’ on center spacing) to form the entire roof. But I can remember designing trusses for a very large and complex roof that had over 60 different truss types to form the completed roof system. Some builders feel that only simple roof designs can be trussed and that complex roofs must be stick framed. That is not true at all. As a former truss designer that really enjoyed the challenge of designing truss systems for complex roofs, I feel that the more complex a roof is, the more reason for using trusses so that the roof loads are made to bear where they should.

Here’s what I mean by the term truss system. Each truss in the roof system is engineered for its specific job based on where it is located within the roof. That way you can be assured that the roof system will carry all the maximum loads as required by code. And because trusses are rarely designed to use interior walls for load bearing, all the roof load forces are transferred to the exterior walls of your home. And those walls sit directly on the foundation which is exactly where those loads need to be placed. In fact, when using trusses it is possible to build and brace the exterior walls, set the trusses on top, and then build the interior walls under roof. Also, remodeling a home that has a trussed roof is easier because you can usually remove any interior wall and change the layout of the interior without affecting the roof.

Now for a side note for those of you who might be interested in the engineering of trusses. Truss design software actually calculates the loading of each piece of lumber and connector plate in the truss. The forces, tension or compression, are calculated as well as the bending tendency of each piece of wood. And the steel connector plates are sized according to the forces at each joint as well as the grade of lumber being used. So there is no guesswork when you use an engineered truss system to form your roof.

Can there be problems with roof truss systems? Absolutely. Anytime people are involved there can be mistakes. So it’s just as important to get your trusses from a reputable truss company as it is to choose a reputable builder. Truss designers can make mistakes. (even me) And so can the truss installers, which is usually the framer.

Each truss system is delivered with a layout showing the location for each truss in the roof. There will also be a truss drawing of each individual truss showing its engineering criteria and also how that truss is to be braced. Bracing must be done exactly as shown on the truss drawing or the truss manufacturer will not be responsible for the truss system’s performance. In my experience, this is the biggest problem with truss systems. Framers simply do not look at the truss bracing diagrams and install the truss based on their ‘professional’ guess. So in a way, that turns the truss system back into a stick framed roof instead of an engineered roof system.

So bottom line is that either a stick framed roof or a trussed roof may be done correctly. And either type of roof framing may be done incorrectly. It all depends on the people you choose to work with.

One other point I’m sure you want to know about. How does the cost of stick framing a roof compare to trusses? In general terms it should be about the same. Trusses are manufactured in a plant by people. That takes time and materials. A stick framed roof is built onsite by people using materials. The cost for time and materials should be approximately the same. But some framers want to charge you as much to set trusses with a 3 man crew and a crane in one day as they charge you for framing the roof using a 5 or six man crew for several days. That’s just wrong. Again you need to choose people who are reputable and whom you can trust. Roof designs, materials, and labor are different in different locations at different times. So the only way you will know which roof system is cheaper is to have it priced both ways.

I hope this article has given you at least a good overview that will be a helpful basis for discussing the roof framing of your new home with your builder.