I Need Somewhere to Land This Thing
In the past few years I have noticed a trend in the residential construction industry. It seems that structures, many times by request from home owners, are becoming more and more wide open. What I mean is that many of the floor plans are increasingly free-flowing from room to room with less and less interior walls to break things up. With wall height variations and numerous roof and ceiling planes, it seems that long gone are the days of the ranch style home.
I will be the first to admit that much of the architecture that we are seeing now is very pleasing to the eye aesthetically. Additionally, some of the combinations of architectural styles are just down right interesting, and challenging to work with. With that being said there are at times some difficulties in designing trusses for them. Simply put, they just don’t consider it.
When a home owner or architect wants to make adjustments to room dimensions, ceiling height steps or when contractors or engineers run into site issues that change the bearing points, things can become difficult. With girders, engineered lumber, and steel it is amazing what can be accomplished. But sometimes I find myself saying “I need somewhere to land this thing”. After all, these are structural components, right?
How many times have you witnessed:
- An architect specifying a 12” coffer, 24” inside the wall on a common heel?
- Maybe an AHU recess on a shallow pitch?
- How about a 10’ ceiling on a 9’ wall?
- The list goes on and on…
This truss referenced below, the architect called out a 12” coffer, 36” inside the wall on a common heel.
Let’s see…on a 2×4 heel, that’s 3”15/16 (heel) + 9” (3/12 run of 3’) + 2” (3/12 run on 8” CBS) = 1’2-15/16”. This would leave only 2”15/16 for the top chord, which on a 3/12 run is 3”11/16 deep!
Well, we got something to work, but it was not what they specified. We ended up with a 5”15/16 heel, an 8” coffer step at 36” inside the wall. It worked alright, but it was expensive! The 30’ span flat-top hip trusses were all 2-ply and the 6’ setback hip girder was 4-ply!!! And every single one of those trusses required a top chord scab, making the common hip trusses a 3-ply there and the hip girder a 5-ply.
At this point in the design process, it is imperative that all parties involved communicate and work together to come up with a solution. Very rarely does a project go off without a problem of some kind (No phone calls back on this one, but I doubt they actually applied those scabs). This is what makes this construction industry so interesting. The chance to learn from others and from every experience and to work with people who are problem solvers as well. There is nothing like being able to look back at the end of the day and know that you were involved in the construction some one’s dream home.
What kind of things have you experienced that helped you?
Rolin Phillips – Design Professional
Gould Design, Inc.