FHB Logo Facebook LinkedIn Email Pinterest Twitter Instagram 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

In every issue you'll find...

  • Expert insights on techniques and principles
  • Unbiased tool reviews
  • Step-by-step details to master the job
  • Field-tested advice and know-how
Subscribe Now!
Subscribe
  • How-To
  • Design
  • Tools & Materials
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
  • Join
  • Log In
Subscribe

Discussion Forum

Discussion Forum

replacing floor joists

pino | Posted in General Discussion on April 16, 2004 01:04am

I need to replace three 2 x 8 floor joists in my 1916 bungalow. They have been notched, cut and shaved down to less than 2 x 4 and are worthless. I plan on removing them and adding new 2 x 10’s planed down to match the existing size. Once completed, I’ll be adding a small i-beam on posts to take up some of the bounce in the floor.

My question is how best to attach the new floor joists to the subfloor above? The subfloor looks like 1x run at an angle to the joists with oak T&G on top. Can I glue them to the subfloor from below? I came apply continual pressure with a number of jacks and temporary posts that I have, until the glue sets up.

Also, what should I use to shim the joists up tight on the ends? They sit atop CMUs. Someone suggested metal shims, but I am unfamiliar with these.

Reply

Replies

  1. JohnSprung | Apr 16, 2004 03:01am | #1

    Why not just leave the old joists in place, and sister the new ones to them.  Glue and nail the new ones to the old ones.  Unless you have substantial dry rot or termite damage, this would be easier to do and make a stronger floor.

    As for shims, metal ones could be just about any piece of steel the right size.  Steel would survive being driven into place a little better, but there's no other advantage.  Since you have the equipment to jack the ends up and take the load off while you shove shims in, you can use shims of the same kind of wood as the joists.  There's no advantage to having shims stronger than the joists.

    -- J.S.



    Edited 4/15/2004 8:08 pm ET by JOHN_SPRUNG

  2. davidmeiland | Apr 16, 2004 06:36am | #2

    You could use Simpson A35 clips to attach the subfloor to the new sistered joists. Use joist hanger nails into the joist and 3/4" #10  round head sheet metal screws into the subfloor.

  3. TrimButcher | Apr 16, 2004 05:30pm | #3

    Glue ISN'T structural...at least, none of the glues you are going to use. It can enhance but not replace mechanical fastening.

    Feel free to glue, but you must use a mechanical fastener.  Preferrably screws over nails. The Simpson A35 would work, but they're not cheap.

    I'd be tempted to use a Kreg pocket hole jig.  Anyone have any reason why this would be a bad idea?

    Regards,

    Tim Ruttan

    1. pino | Apr 16, 2004 05:39pm | #4

      My father-in-law has a Kreg jig. What kind of spacing would you recommend.

      1. TrimButcher | Apr 18, 2004 12:36am | #20

        Frenchy's suggestion of toe-screwing without using a Kreg jig was my first thought.  Sheetrock screws certainly weren't.  However, I suggested Kreg because it would give you perfect control of the depth of screw penetration into the subfloor.  Wouldn't want to penetrate the subfloor into the flooring.  Okay with hardwood, not so good with linoleum or tile.

        David's suggestion that the Kreg screws might split the edge off the joist doesn't seem to me to be a likely problem. The predrilled holes and screws don't have the wedging action that nails have that can cause splitting. You can alternate which side of the joist you drill to further prevent splitting.

        As far as a screwing schedule goes, perhaps Piffin can advise.  I don't deal with plank subfloors in my neighborhood.

        Regards,

        Tim Ruttan

        Edited 4/17/2004 5:38 pm ET by TRIMBUTCHER

        1. fdampier5 | Apr 18, 2004 05:09am | #21

          I understand your reluctance to use sheetrock screws,   Heck it's not a major issue with me. use whatever screws you wish,  I certainly can't claim any loyalty to sheetrock screws,  they aren't terribly strong and won't handle much load but the direction of load is in their favor in this instance. 

           I won't use my Kreg screws in this application because they are very expensive and  won't offer any real advantage over simple sheetrock screws.. (in this application..

                I would use one screw per plank. plenty enough to  avoid squeeking (which is the only thing these screws will ever do)

        2. JohnSprung | Apr 20, 2004 02:41am | #22

          Is there really a need for toe-screwing here?  If the subfloor is securely nailed to the old joists, and you secure the sisters properly to the old joists, then the whole thing is structurally sound.  Adhesive as an anti-squeak measure between the subfloor and sisters, and between the old joists and sisters, would be all you'd need.  Why risk effing up the finished floor above?

          -- J.S.

          1. Piffin | Apr 20, 2004 03:12am | #23

            i'll go along with that! 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          2. pino | Apr 20, 2004 03:54am | #24

            And so will I. Thank you all for your advice.

  4. fdampier5 | Apr 16, 2004 06:08pm | #5

    I'd simply sister the new jiost alongside the old and then I'd nail them together well followed by screws(dare I say sheetrock) run in at an angle   as if you were gonna toenail..     Sure kreg screws would look nicer but is that important?  why not save the time and money and just run some screws in place.

      As for the glue idea,  My feelings are that unless the old floor was glued (extremely unlikely) you won't gain anything with glueing the new joist in (except maybe a bigger mess)   I would put the ends on metal though.. you do not want to conduct the ground moisture up into those beams..

      Finally,  I don't know that I would go to all the effort to put a 2x10 in.. sure modern 2x8's are smaller but you could easily make up that differance with a strip of plywood or osb on the bottom for nailing purposes

    1. davidmeiland | Apr 16, 2004 08:59pm | #6

      Pocket screws might be a way of fastening to the subfloor, but bear in mind that most pocket screw applications have the drilled hole and the screw parallel to the grain, not perpendicular. The threads are perpendicular to the piece they bite into. A long row of pocket screws down the edge of a joist will probably just split the edge off, either now or later.

      Drywall screws are useless in a structural application like sistering joists. They are also pretty much useless for hanging cabinets, which everyone does anyway. They are brittle and have very little shear strength. They are good for hanging drywall. You'll never see an engineered detail connecting framing lumber with drywall screws. The accepted fasteners are good ol' fashioned machine bolts, carriage bolts, or spikes. Glue will help prevent squeaking, so definitely use it against the subfloor.

      1. fdampier5 | Apr 17, 2004 01:54am | #7

        I think I can disagree here,  not that I love sheetrock screws but think about what is trying to be achieved here.  there is no real load.  All we are trying to do is insure that the subfloor above doesn't move in relation to the new sistered joist  (and cause the floor to squeek)  the joist is providing the ability to carry the load.  Nails are keeping the joist from moving sideways.  (because it's sistered alongside the original joist)   all the screws will do is provide that last bit of insurance to prevent the subfloor from moving relative to the original sistered joist..

          siting right next to the original joist at the very mosy the subfloor has 1 1/2 inch to expand and contract.. In the inpossible event the joist gets wet while the subfloor remains dry (or visa versa)  there still is too little wood involvement to provide much risk of a squeek over and above what is already there. 

          Mind you they did not glue and screw subfloor down at the time the house was built.. What you are attempting to do is bring a vintage floor up to modern code in amybe 1/100ths of the total area involved..  not real practical..

        1. davidmeiland | Apr 17, 2004 03:38am | #8

          Sorry, Frenchy, misread your original comment. Yes, you could definitely use SR screws from joist to subfloor. In my haste I thought you were saying joist-to-joist. I'd still use deck screws because I think drywall screws break too easy. Maybe that's because I'm so clumsy with my screwguns.

          1. Piffin | Apr 17, 2004 04:09am | #9

            No, it's because SR screws are acheaper grade of meal and not designed for structural applications like this. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          2. fdampier5 | Apr 17, 2004 05:48am | #12

            this isn't structural.. it's to prevent movement..

          3. Piffin | Apr 17, 2004 06:15am | #14

            so what causes movement in a floor?

            Loads, that's what.

            any member subject to loading is structural. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          4. fdampier5 | Apr 17, 2004 05:59pm | #17

            floor joists that have lasted 90 years are probably  strong enough for the loads encountered.. what we are attempting here is to limit the movement of wood relative to other wood in order to eliminate additional squeeks..

               (I'm willing to bet there are spots on this floor that squeek already)  most likely the close proxiity of a sistered joist won't cause much (if any) additional squeeks.  The screws merely ensure that they won't.  Kinda a belt and suspender kind of approach..

          5. Piffin | Apr 17, 2004 11:24pm | #19

            Well, excuse me for my comment, but I was doing something different than you were, apparantly. See,the first post adressed the idea of replacing them because they are worthless. That means the new ones will be bearing a load. I must have moissed the part where you can have a floor joist that does not handle loads.

            stupid me 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          6. rez | Apr 17, 2004 06:06pm | #18

            Only frenchy would want a cheap snack of sheetrock screws to munch on.

            Holy Cow!

            Alright, but the next time I'm charging ya.

          7. fdampier5 | Apr 17, 2004 05:47am | #11

            I'm not a fan of sheetrock screws except where only modest level of strength is called for.  Then I like them because they tend to be sharper and dig into wood easier than deck screws do..

  5. Turtleneck | Apr 17, 2004 04:26am | #10

    I'd go with the sistered 8" stock as well. If you want some extra strength check for full 2" stock at a local saw mill. Probably alot cheaper than kiln dried 2 X10s too. You could lag bolt the old joist to the new or drill and bolt the two of them together. Nails or screws never pull them together like a bolt and ratchet.

    Use sub-floor adhesive for fastening the floor to the new joist. A good bead of it squeezed on the underside of the floor before setting the joist should take care of any future sqeeeeks quickly and permanently.

    I don't see any advantage of using 2 X10s if you have to knotch them for beams.

    My two cents

    Gord

    1. fdampier5 | Apr 17, 2004 05:52am | #13

      Here's a little tip,  always remember to predrill for a lag bolt thru the first layer of wood.    I drill the size of the shank, ie a 1/2 inch lag bolt gets a half inch hole..

        the screw then pulls the second layer of wood tight..

       if you don't predrill the first layer any gap you have between boards will remain..

      1. Turtleneck | Apr 17, 2004 04:42pm | #15

        So...predrill for lags in old joist before the new one goes up?

        1. fdampier5 | Apr 17, 2004 05:47pm | #16

          Yes! I wouldn't use anything larger than 3/8ths for floor joists their shear strength is more than enough if you space them properly (about 12 inches on center)

            I'd rather use a lot of smaller fasteners than a few large ones.  Two reasons,

             first redundancy..

              If the spot that connects the wood is flawed in any way other fasteners are there to carry the load..

             Second,...

               You'll get better connection with a number of fasteners than a few.

            Now I cheat because I use my air impact wrench and it is but a moments work to run a lag in.  if you are going to wrench them in by hand I'd drill a pilot hole once the new joist is sistered in place.  Actually a pilot hole is a great idea to use at any time because it makes the fastener hold much better.. If you jam the lag bolt into the wood,  the threads and shank need to crush the fibers enough to make room for themselves. Predilling a pilot hole avoids that! use a drill bit about 10% smaller than the root of the lag bolt..

          Edited 4/17/2004 11:00 am ET by frenchy

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Video Shorts

Categories

  • Business
  • Code Questions
  • Construction Techniques
  • Energy, Heating & Insulation
  • General Discussion
  • Help/Work Wanted
  • Photo Gallery
  • Reader Classified
  • Tools for Home Building

Discussion Forum

Recent Posts and Replies

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

Up Next

Video Shorts

Featured Story

Tools for Managing Home-Building Financials

Production manager Ian Schwandt explains how financial tools such as QuickBooks or Buildertrend can help companies track project costs for a healthy outcome.

Featured Video

Video: Build a Fireplace, Brick by Brick

Get an overview of the process of creating a traditional-style fireplace that burns well and meets current building codes from experienced mason Mike Mehaffey.

Related Stories

  • Podcast 485: Air-Sealing a Mobile Home, Owner/Builder Tests, and Ready-to-Tile Shower Bases
  • Podcast 485: Members-only Aftershow
  • Fastener System for Solving Deck Fascia Board Expansion
  • Improve Home Efficiency With Inflation Reduction Act Rebates

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

BOOKS, DVDs, & MERCH

Shop the Store
  • Outdoor Projects
    Buy Now
  • Pretty Good House
    Buy Now
  • Code Check Building 4th Edition
    Buy Now
  • 2021 Fine Homebuilding Archive
    Buy Now
  • Shop the Store

Fine Homebuilding Magazine

  • Issue 309 - Aug/Sept
    • 10 Steps to Install Crown Molding on Cabinets
    • How to Get Sturdy Walls Without OSB
    • Choosing the Right Construction Tape for the Job
  • Issue 308 - July 2022
    • Pretty Good House Book Excerpt: Copper Farmhouse
    • 10 Dos and Don'ts for Electric In-Floor Heat
    • A Sturdy Rail for Outdoor Stairs
  • Issue 307 - June 2022
    • How to Raise a Post-Frame Home
    • Trimming Deck Stairs
    • Evolving an Energy-Efficient Envelope
  • Issue 306 - April/May 2022
    • Framing Stairs to an Out-of-Level Landing
    • Building a Zero-Energy Home for Less
    • Good-Looking and Long-Lasting Traditional Gutters
  • Issue 305 - Feb/March 2022
    • The Steady Surge in Residential Solar
    • The Fine Homebuilding Interview: William B. Rose
    • How Good Is Your Air Barrier?

Fine Homebuilding

Follow

  • twitter
  • facebook
  • instagram
  • pinterest

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

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences

Taunton Network

  • Green Building Advisor
  • Fine Woodworking
  • Fine Gardening
  • Threads
  • About
  • Contact
  • Advertise
  • Careers
  • Copyright
  • Terms of Use
  • Site Map
  • Do not sell my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2022 The Taunton Press, Inc. All rights reserved.

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
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Account

  • Log In
  • Join

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

Shop the Store

  • Books
  • DVDs
  • Taunton Workshops

More

  • FHB Ambassadors
  • Reader Projects
  • Podcast
  • 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

  • twitter
  • facebook
  • instagram
  • pinterest

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