In Texas, residential construction doesn’t always require the use of a structural engineer to design the frame. This is likely because most single-family homes have relatively simple framing. However, a structural engineer should be used when the design becomes complex. A four-story custom home with an unusual floor plan was designed by an architectural designer without consulting a structural engineer to design the wood structural framing. The builder, using the architectural design, hired a truss manufacturer to design and provide open-webbed wood trusses and beams for the home, but the builder did not seek an engineer to design the vertical or lateral-load resisting systems.
After the homeowners occupied the home, cracking of the architectural finishes and water damage were observed inside the home. Several investigations were performed to determine the cause and look for viable solutions.
We were retained to evaluate the design of the truss system to see if it was the cause of the distress. We performed an independent analysis of the truss and beam designs. One of the unusual things that we considered was a hot tub that had been placed on the roof of the house, which had been implicated as a potential cause of the distress by one of the other investigators. We concluded that the trusses and beams supplied by the truss manufacture were adequately designed, even with the hot tub weight. The distress actually resulted from problems with the vertical framing system.
This home showed the importance of having a custom/unique structure properly engineered. Standard construction span tables and framing methods do not fully account for the complexities associated with many custom structures. Had an engineer been involved in the complete design of the home, many costly errors could have been avoided.