Truss Design: Doing the Impossible

As truss designers, we are fortunate to have built into our job description constant mental stimulation. Our job is really about putting “pieces of the puzzle” together and “making everything fit”. Sometimes we run into design project assignments that cover all 3 aspects I have just mentioned. This article is about one such project.


This particular assignment is one of those that have just about every condition you can think of in it. It would have helped if the building designer would have taken the time to figure out how to support all of these unusual conditions, but, thankfully, he left that up to me. This job was so mentally stimulating that I found it hard to walk away from it when it was time to go home.

I won’t take space to relate all of the details of the project; rather I want to focus on 2 particular conditions that a truss designer just does not see every day and hopefully inspire some creativity for when you run into something like this in the future.

Radius Wall Framing

As you can see, this project has a radius tower at the entry. The problem is, below this tower is totally open to below and no bearing is available to support it. In fact, in the first draft of the architectural plans, the radius was pushed back 7’ from where it is now, making it impossible to support. This is what I came up with to solve the problem.


To say this was fun is an understatement. It took a great deal of thought and careful mathematics to even consider this type of solution. It requires trusses on 2 different levels to transfer loads down to the foundation in order to support this 19’9” radius tower.


Upper Loft Framing

This project also had another fun challenge to overcome. There is a sloping flat roof that connects to an upper loft balcony overlook that is open to below.


In order to access this loft, some imagination had to be used, as the ceiling height over the stairway was on a plane sloping down. I ran some butt-cut, tail-bearing monos that bear directly on top of monos at the level below at one end and hang into a sloping flat girder at the other end.  Fun!

In addition, the sloping roof had to be turned and supported by the loft beam to avoid having to place loads down to a beam in the floor system that barely worked carrying only wall, jacks and floor loads.


What types of creative design have you run into recently? How did you “Do the Impossible”