Basic Load Paths
Have you ever had an inspector tell you to add a strap (tension tie) to some framing for a “positive connection” and when you asked what that meant, you got a non answer? Truth is it took me a ton of time to find a definition and reference.
In wood framed light construction we’ve become very good at designing and constructing strong buildings that are proving to be very resilient to earthquakes and hurricanes. Fully sheathing our walls contributes greatly to this, but another important component in framing is the load path.
We instinctively understand some load paths. If we have an opening in a wall and a floor or roof above it, we bridge that opening with a header. That header transfers the loads from above to columns or framing that bear on something else, e.g. floor, foundation wall, etc that will transfer that load to the ground. One comment on a webinar by the Engineered Wood Association was that one way or another a load will meet the ground, either through transfer of structural members or building collapse.
Over the years in the field I would have a inspector point out where I had missed “positive connections” between structural members and I didn’t always understand what he was referring to. Thankfully our engineer walked a house I framed and took the time to explain it to me.
Where I live and work, we build to the International Residential Code (2015 currently). R301.1 Application states “Buildings and structures, and parts thereof, shall be constructed to safely support all loads, including dead loads, live loads, roof loads, flood loads, snow loads, wind loads and seismic loads as prescribed by this code. The construction of buildings and structures in accordance with the provisions of this code shall result in a system that provides a complete load path that meets the requirements for the transfer of loads from their point of origin through the load-resisting elements to the foundation. Buildings and structures constructed as prescribed by this code are deemed to comply with the requirements of this section.” (bold mine)
What does a “positive connection mean”? FEMA defines it this way
That statement “otherwise positively fastened without consideration of frictional resistance produced by the effect of gravity” makes this clearer for me. I often thought “well the weight of the building is holding that beam in place plus the joists themselves”. Below are a few examples of “positive connections”.
Walls are strapped together under the beam, but the beam needs to be strapped to triple 2x6.
This balloon framed rake wall needs to be strapped horizontally at the 4x6 “fire blocking” (which is also the panel edge blocking for the sheathing) to the double top plates
The same wall as the previous photo. The upper row of blocking needs to be strapped to the double top plates of the
double top plates of the level portion of the wall
