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
Tips & Techniques

Fixing a Broken Floor Joist

A lightweight car jack may be the answer to repairing tricky floor joists.

Issue 164
Click here to enlarge illustration. Edited and illustrated by Charles Miller.

When our 1920s farmhouse was moved in the ’70s, it gained a new foundation and a couple of broken floor joists. The joists never were repaired, so by the time we bought the house, the floor had some distinctly springy spots.

Working from below in a full basement, it seemed an easy proposition to sister a new joist to the side of a broken one. However, my first attempts at bringing the joists together with C-clamps didn’t work very well. I couldn’t exert enough pressure to the top of the new joist to bring it flat against the old one.

As shown in the drawing, I ended up using the lightweight jack from my wife’s compact car to get the job done. It allowed me to work my way along the length of the joist, pressing it into place and nailing it to the broken joist. To keep the joists aligned on each side of the work, I used a pipe clamp to counter the force of the jack.

— John Mares; Dassel, MN

From Fine Homebuilding #164

RELATED STORIES

  • The Science of Simple Spans
  • Straightening a Humped Joist
  • Floor-Joist Reinforcement

Got a Tip?

Do you have any great tips like this one on how to fix broken floor joists? Share your methods, tricks, and jigs with other readers. Tag them @FineHomebuilding on social, email them to us at [email protected], or upload them to FineHomebuilding.com/reader-tips. We’ll pay for any we publish.

Sign up for the Fine Homebuilding Tip of the Day and get daily tips and special offers delivered to 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
×

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

View Comments

  1. user-1102188 | Sep 13, 2016 08:04pm | #1

    Better to use screws verses nails?

    Bob

  2. paul_remodel | Sep 14, 2016 08:44am | #2

    Sometimes the old joists will be bowed. What I do if there is room below the old joists is to place a 4x4 under the old joists where it is the lowest, leaving enough space for a 2 ton jack below the 4x4, and gently jack it up until it matches the new sister joists, and then bolt them together. Just a thought.

  3. ktkcad | Nov 28, 2018 10:54pm | #3

    Nails are good in this situation as they 'flex' as the joist's live load changes. This may add to 'squeeks' but that gives the house 'character'. Either will work in the long run.

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

More Tips & Techniques

View All
  • Hand-Sanding Hack
  • Custom Cabinet Pullout Drawer
  • Old-Sock Safety Kit
  • Simple, Site-Made Trusses
View All

Up Next

Video Shorts

Featured Story

Fast, Accurate Wall Framing

A rear addition provides a small-scale example of how to frame efficiently.

Featured Video

Builder’s Advocate: An Interview With Viewrail

Learn more about affordable, modern floating stairs, from design to manufacturing to installation.

Related Stories

  • Old House Air-Sealing Basics
  • Pressure Washing Made Portable
  • FHB Podcast Segment: Designing and Building an Efficient Slab-On-Grade Home
  • Seven Ways to Remove Paint

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
  • FHB Podcast Segment: Designing and Building an Efficient Slab-On-Grade Home
  • FHB Podcast Segment: Sealing a Floor Cavity in a Slab-on-Grade House
  • Podcast 606: Foam Slabs, Gaps in Click Flooring, and Board and Batten Rainscreens
  • Podcast 587: Members-only Aftershow—Basement Flooring
View All

Maintenance and Repair

View All Maintenance and Repair Articles
  • Seven Ways to Remove Paint
  • Ranch Redux
  • Restoring Polychromed Light Fixtures
View All Maintenance and Repair 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 2025
    • 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.

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

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