Who Decides Roof Truss Layout Placement & Orientation?

I would like to post a question for discussion.  In this discussion, I am referring to a roof that is required to have sealed engineering. I would love to hear everyone’s opinion on this topic, as this is a question I am sure every single one of us has pondered at one time or another.

truss-placement-orientation

Who decides how and why a trussed roof gets laid out?  Is it:

  • The Customer who is purchasing the roof trusses?
  • The Building Designer or Architect that drew the plans?
  • The Roof Truss Manufacturer who will be producing the roof trusses?

Should the Customer (Usually the home builder) determine:

  1. Where the starts and stops should be?
  2. What the hip setbacks should be?
  3. Where the girders should be placed?
  4. What types of jacks and hips are to be used?

Ultimately the Customer is paying for the truss package that is delivered.  They are the ones responsible for erecting and installing the truss package properly.  And they are also responsible for any potential over framing there might be associated with a specific truss package.

For instance, do they want valley trusses included behind girders?  Do they want their hips to follow all roof planes, in what I call a “Rocky Mountain truss?”  It is after all, what they are paying for and they are going to pay for it in the truss package or through the framers on the job.

Should the Building Designer/Architect determine everything that has to do with the roof?  These people have spent more time looking at the individual project than anyone else involved and should have a better idea of where the roof structure should be placed to best transfer through all levels.

On a lot of plans I see 6×6’s placed vertical in exterior walls to pick up loads from hip masters or other girders.  The designer here has a plan for transferring load from the roof down, and potentially through multiple levels.  If the setback of a Hip Master or girder is moved to suit the desires of the customer or truss manufacturer, who’s to say that the 6×6 or the material below it, has been adjusted to compensate for the move?

On the “flip side” of that coin is what we have all seen: framing plans that just are not feasible. Such as trusses running the 80’ span, rather than the 40’ on an 80’x40’ building. Or maybe a Hip Jack that is 30+ feet long tying into a hip girder without consideration of that connection. More common though is when we have a ceiling condition that runs through a girder system that just is not possible.

Should the Truss Manufacturer determine how a roof gets laid out?  Ultimately, the truss manufacturer and their engineers are the ones responsible for the structural stability of the roof.  They are also the ones that are often times held to a set price that was determined long before the trusses ever went into production.  The truss manufacturer also has a deadline to meet in the delivery date.  So time is of the essence in the manufacturing plant.  If the process can be streamlined to simplify production, decrease costs, and hit delivery dates, it is beneficial for the truss plant to manipulate the roof layout to suit their needs.  Adding trusses to a layout that pick up all roof planes tends to add time to production versus building a straight run of trusses that are easier to produce, but a customer may have to do a little work in over framing.

Ultimately, who should have the right or ability to determine the roof layout of a non-engineered structure?  The Customer who is ultimately the one paying for it?  The Building Designer/Architect that has spent the most amount of time working on the structure?  Or the Truss Manufacturer who is responsible for the roof, price, and delivery date?

Design Administration

Gould Design, Inc