I-Joist Roof Framing and Construction Details

EWP Training Series: Module D

This module introduces trainees to best practices in the design of engineered roof systems. It includes recommendations for the proper use of joist hangers, squash blocks and web stiffeners for transferring roof loads for a variety of common roof types. It also includes a review of framing details and recommended notching and drilling practices to maintain structural integrity. No CEUs available at this time.

No CEU credits are available, but you may obtain a certification of completion by clicking the "Get Certificate" option that will appear after viewing the entire video on this webpage. Do not navigate to YouTube if you require a certificate; downloadable certificates are unavailable on the YouTube platform.

Training objectives: Upon completing this course, students will be able to identify and describe:

  • Best practices in designing and detailing residential engineered wood roof systems
  • Proper techniques for connecting, notching and drilling I-joists in roof systems
  • Proper techniques for notching and drilling I-joists and Rim Board
  • Correct use of web stiffeners and blocking in I-joist roof systems
 
Approximate length: 25 minutes.

Participant Questions and Answers

Can I-joists be cross ventilated in a roof application?

Yes, of course depending on the depth of the insulation vs. the joist depth, check with your specific manufacturer for guidance as to hole cutting for cross ventilation.

You didn’t cover much on uplift, how do I learn more?

Uplift design is varied based on area wind speeds, building exposure and other factors. Consult with your product manufacturer for details related to your specific situation and location.

Do the joists always need to be doubled next to framed openings in the roof?

Not always, the doubling requirement depends on the size of the opening and the loads involved. Most proprietary software can calculate whether a single or double joist will be required.

Is there a max pitch for I-joist use in roof systems?

Check with the manufacturers for the max pitch or special design requirements stated for specific I-joist brands and situations.

When having a ridge beam supported by I-joists, is there a specific depth you need in regards to the depth of the ridge beam?

Sounds like this question may be referring to a ridge board. With EWP, the beam must support the I-joists, not be supported by them. As a carrying beam, the member should be sized to carry the load required and be large enough for the attachment of the required hangers.

Is the APA Form D710 the APA reference for roof design?

APA form D710 is an installation guide for roof systems which contains the details discussed in the webinar. The guide is available as a free download from our APA website. You should always check the I-joist manufacturer’s literature for their specific roof construction recommendations.

There are a lot of additional required pieces of blocking and stiffeners and their connections. How does this affect the cost of this system vs. dimension or LVL members?

In making any comparisons-- we need to look at the reasons for using an I-joist roof system. An I-joist roof system does things that a dimensional lumber system cannot do. It can provide cross ventilation, holes for mechanicals and longer spans. It is also lightweight compared to the other two choices. While it is also able to span greater distances, LVL requires similar blocking and hangers. It also has more restrictive hole requirements and may have a higher system cost. Dimension lumber may be cheaper per lineal foot but it also requires blocking and sourcing higher grade, straight 2x12’s in long lengths may be difficult. An engineered wood system may cost more but it permits designs that were not previously possible with 2x material..