FHB Logo Facebook LinkedIn Email Pinterest Twitter X Instagram Tiktok YouTube Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Restoration
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In
How-To

Split Jacks When Framing a Window Opening

Split jacks let you work faster, but they introduce another hinge point in the wall, which could be problematic in high-wind and high-seismic-risk zones.

By Andy Engel Issue 270 - Oct/Nov 2017
  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

When framing a window opening, should the jack or trimmer studs be continuous, or should they split around the rough sill?

—Jerry Riga, via email

This is an interesting question with no clear answer. Jack studs (or trimmer studs—the name depends on where you’re located), provide the load path from the header to the bottom, or sole, plate. Not even the IRC is clear about whether they can be split. Section R602.3 reads, “Studs shall be continuous from support at the sole plate to a support at the top plate,” but then includes an exception for “jack studs, trimmer studs, and cripple studs.” The wording is tricky. It could be that the IRC makes this exception because jacks are always cut shorter than regular stud height in order to fit below the header, or it could mean it’s OK for the jacks to be split around the rough sill. While all the drawings in the IRC show continuous jacks, and many inspectors will fail split jacks, this appears to be a regional preference.

Some carpenters like split jacks because it allows them to nail through the king stud into the end of the rough sill (with continuous jacks, the connection to the sill is normally toenailed), and the lower portion of the split jacks support the rough sill without having to add cripple studs. Simply put, using split jacks lets you work faster.

However, split jacks do introduce another hinge point in the wall, which could be problematic in high-wind and high-seismic-risk zones. Another issue is the horizontal wood grain in the rough sill. Wood has much more compressive strength parallel to the grain than across it, so there’s a chance of the rough sill crushing under, say, a heavy snow load. The counter to this point is that all the plates and the header run horizontally, so what’s the difference?

Although it is frowned upon by advocates of advanced framing—who strive to avoid all unnecessary framing—you could also run the jacks continuously and add cripple studs below the ends of the rough sill. This supports the sill and avoids unwanted conversations with your inspector, although placing lumber where insulation could be installed increases thermal bridging.

Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters
×

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

New Feature

Fine Homebuilding Forums

Ask questions, offer advice, and share your work

  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

View Comments

  1. JLYoung | Sep 17, 2017 08:24am | #1

    I suspect that the IRC considers the king stud to carry all the lateral wind load since it acts as a pinned beam form the top plate to the bottom, thereby simplifying the load path and design. The connection from the header to the jack acts as a hinge point so the jack is typically not considered to resist wind loading. I have two arguments against splitting the jack. The first is that though you are correct about the perpendicular grain resistance being lower than parallel to grain. Your comparison to the top and bottom plates is erroneous. The perpendicular to grain resistance depends on how close the applied load is to the edge of a board. When the compression is right at the unsupported edge of the sill there is a higher tendency to crush than say if the load were applied away from the edge. The second argument is one of durability. I would argue that the window sill has a somewhat higher potential for rot than the sole plate so by splitting the jack and placing the end grain of the jack stud ( a structural member) in the plane of higher rot potential is less desirable location than running it to the bottom plate.

  2. EddyWouldGo | Oct 02, 2017 07:59pm | #2

    "Another hinge point in the wall". Seriously? Is this hinge effect not negligible compared to the shear bracing provided by a properly sheathed and nailed wall? Seems like that hinge effect is way off into the margins, but I am happy to be told how I am wrong and learn.

  3. laketime | Dec 12, 2017 02:11pm | #3

    All these are good points, but arguably of very little actual effect, especially if the jack studs are nailed to the king studs like we practice. We try to avoid toenailing an unsupported joint like with the continuous jack stud, where you need to keep things straight and level.

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Up Next

Video Shorts

Featured Story

FHB Podcast Segment: Are Single-Room ERVs the Answer?

Learn more about the pros and cons of single-room ERVs.

Featured Video

SawStop's Portable Tablesaw is Bigger and Better Than Before

The 10-in. Jobsite Saw PRO has a wider table, a new dust-control port, and a more versatile fence, along with the same reliable safety mechanism included in all SawStop tablesaws.

Related Stories

  • Fire-Resistant Landscaping and Home Design Details
  • Making and Installing Wood Wall Paneling
  • FHB Podcast Segment: Sometimes Spray Foam Makes Sense, Sometimes It Doesn't
  • Beat the Heat: Cool Innovations

Discussion Forum

Recent Posts and Replies

  • |
  • |
  • |
  • |
  • |
  • |
View More Create Post

Highlights

Fine Homebuilding All Access
Fine Homebuilding Podcast
Tool Tech
Plus, get an extra 20% off with code GIFT20

"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Video

View All Videos
  • Making and Installing Wood Wall Paneling
  • FHB Podcast Segment: Sometimes Spray Foam Makes Sense, Sometimes It Doesn't
  • Putting Drywall Sanders to the Test: Power, Precision, and Dust Control
  • FHB Podcast Segment: Drywall-Free Half Wall Finish
View All

Windows

View All Windows Articles
  • Window Glazing with Traditional Putty
  • Tom Gensmer, Remodeler and Window-Repair Expert
  • Shim Trim With Screws
View All Windows Articles

Fine Homebuilding Magazine

  • Issue 332 - July 2025
    • Custom Built-ins With Job-Site Tools
    • Fight House Fires Through Design
    • Making the Move to Multifamily
  • Issue 331 - June 2025
    • A More Resilient Roof
    • Tool Test: You Need a Drywall Sander
    • Ducted vs. Ductless Heat Pumps
  • Issue 330 - April/May 2025
    • Deck Details for Durability
    • FAQs on HPWHs
    • 10 Tips for a Long-Lasting Paint Job
  • Issue 329 - Feb/Mar 2025
    • Smart Foundation for a Small Addition
    • A Kominka Comes West
    • Making Small Kitchens Work
  • Issue 328 - Dec/Jan 2024
    • How a Pro Replaces Columns
    • Passive House 3.0
    • Tool Test: Compact Line Lasers

Fine Home Building

Newsletter Sign-up

  • Fine Homebuilding

    Home building tips, offers, and expert advice in your inbox.

  • Green Building Advisor

    Building science and energy efficiency advice, plus special offers, in your inbox.

  • Old House Journal

    Repair, renovation, and restoration tips, plus special offers, in your inbox.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters

Follow

  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X
  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences
  • About
  • Contact
  • Advertise
  • Careers
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2025 Active Interest Media. All rights reserved.

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

  • Home Group
  • Antique Trader
  • Arts & Crafts Homes
  • Bank Note Reporter
  • Cabin Life
  • Cuisine at Home
  • Fine Gardening
  • Fine Woodworking
  • Green Building Advisor
  • Garden Gate
  • Horticulture
  • Keep Craft Alive
  • Log Home Living
  • Military Trader/Vehicles
  • Numismatic News
  • Numismaster
  • Old Cars Weekly
  • Old House Journal
  • Period Homes
  • Popular Woodworking
  • Script
  • ShopNotes
  • Sports Collectors Digest
  • Threads
  • Timber Home Living
  • Traditional Building
  • Woodsmith
  • World Coin News
  • Writer's Digest
Active Interest Media logo
X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Project Guides
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

Online Learning

  • Courses
  • Project Guides
  • Reader Projects
  • Podcast

More

  • FHB Ambassadors
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • X
  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 70%

Subscribe

This is your last free article.

Don't miss another expert tip or technique from building pros. Start your free trial today.

Start your FREE trial

Already a member? Log in

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in

Privacy Policy Update

We use cookies, pixels, script and other tracking technologies to analyze and improve our service, to improve and personalize content, and for advertising to you. We also share information about your use of our site with third-party social media, advertising and analytics partners. You can view our Privacy Policy here and our Terms of Use here.

Cookies

Analytics

These cookies help us track site metrics to improve our sites and provide a better user experience.

Advertising/Social Media

These cookies are used to serve advertisements aligned with your interests.

Essential

These cookies are required to provide basic functions like page navigation and access to secure areas of the website.

Delete My Data

Delete all cookies and associated data