At first glance, it looks wrong—your I-joists don’t line up flush with the rim board. But that’s not poor framing…it’s how engineered floors are designed to work.

In this Rational Spec episode, we explain why floor systems are built this way and break it down in plain language so it makes sense whether you’re a homeowner, DIYer, or pro framer.

What you’ll learn:

• Why rim boards are taller than I-joists
• How load paths work in engineered wood floors
• The purpose of web stiffeners & squash blocks
• Tricks for staging and cutting long I-joists efficiently
• Blocking details that matter in seismic zones
• Simple tips to frame smarter, not harder

If you’ve ever looked at a floor system and thought “that can’t be right”—this video is for you.

📚 Resources:

• APA Engineered Wood Association → apawood.org
• PWT I-Joist Guides