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

Discussion Forum

Discussion Forum

Second layer of OSB subfloor

LarryY | Posted in Construction Techniques on July 6, 2012 09:03am

I’m looking for some advice on adding a second layer of OSB to a 3/4″ T&G subfloor.  This is new construction.  3/4″ T&G was rained on several times.  Some flaking.  I-joists are 16″ oc.  I’m thinking of adding a layer of  1/2′ or 5/8″ OSB on top of the 3/4″ T&G after the roof is on, which should be mid-next week.  3/4″ T&G is glued and nailed.  Question I have is “If I add a second layer of OSB should it run the same direction as the first layer and overlap the seams or should it run perpendicular to the first layer?”  Glue and nai lto the joists as the first layer or maybe screw it thru the first layer?  Thanks for any advice.  Larry.

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

Replies

  1. florida | Jul 06, 2012 09:21pm | #1

    A little rain shouldn't hurt OSB but another layer would make your floor stiffer so why not. I'd lap all the joints in both directions and screw it down to the joists.

    1. User avater
      xxPaulCPxx | Jul 08, 2012 04:03am | #5

      I thought - to prevent squeeks - you were supposed to attach the 2nd layer to the subfloor below, not the floor joists.

      1. DanH | Jul 08, 2012 07:20am | #6

        I'm trying to think how that would prevent squeeks.  Certainly one should screw BETWEEN joists as well.

  2. User avater
    LarryY | Jul 06, 2012 11:03pm | #2

    Thanks for the reply, Florida.

  3. calvin | Jul 07, 2012 09:27am | #3

    Larry

    How's the adding going to affect your door openings and stair rise?

    1. User avater
      LarryY | Jul 07, 2012 04:37pm | #4

      I think I can adjust the stairs. More of a concern is the entry doorways.  Ledger board is already attached forthe outside deck so that there's no step up/step down.  Adding new layer of OSB will mean the deck will be 5/8" or 1/2" lower than planned.  No too much of a height difference but just enough to trip and be a real nuisance.  I guess I could add some quarter round treated molding at the doorways/deck .  Any suggestions?  Thanks

      1. calvin | Jul 08, 2012 07:25am | #7

        Suggestion?

        At the deck, cut a trim that will "ramp up" to the threshold of the door.  Feet will sweep up and over with little chance of trippage because there won't be a sharp or severe lippage.

      2. MasterCarpenterAce | Jul 11, 2012 08:14pm | #9

        not to count every door in the house that swings over carpet and its padding or hardwwod or tile will all have to be modified or you headers in every door should go up...also some code say if your windows are below 32" then  and are more than 4.5 sq.ft. then they should be shatter resistant to prevent fall threw accidents...which adds to the cost of the window as well.

        1. calvin | Jul 11, 2012 09:43pm | #10

          Ace

          Are you referring to the newer version of the IRC re. glass?

          I ask because here in NW Ohio, it has always (since in the 70's at least) been glass within 18" of floor, tall glass (6') was always made up tempered and anything within 30/36" of a door (and the door glass itself).  Add to that glass in or within 32" of a tub or shower..............

          But 32"?  Never heard of that.?  I'd question the 4.5 s.f. also-that'd only be less than a 2 x 2'-6" sash.  

          Just trying to clear up the question and/or learn about the newer codes that haven't really hit Ohio yet.

          thanks.

  4. gbaune | Jul 09, 2012 07:13pm | #8

    OSB Flooring

    If you go to the trouble of the second layer, glue and screw.  Overlap the seams in both directions, use screws long enough to reach the joists, should be a nice stiff installation.

  5. ericpaul | Jul 07, 2013 04:19pm | #11

    second layer of subfloor

    i do not understand totally your answer here===I'd lap all the joints in both directions ==does that mean you would alternate the direction that you apply the osb or continue in the same direction but alternate the joints

    1. calvin | Jul 07, 2013 06:54pm | #12

      ericpaul.

      Lap'd both directions means that the long edge would be staggered as well as the end of the sheets----from the first layer.  No edge would line up one layer to the other.

      I think.

      1. DanH | Jul 07, 2013 09:15pm | #13

        Here I was thinking it meant you poured cream along the joints and let the cat in.

  6. IdahoDon | Jul 08, 2013 11:15pm | #14

    If the first layer is only nailed I'd definitely screw through both layers into the floor joists.  Stagger the joints as suggested and use plenty of construction adhesive and screws. I see no benefit to using 1/2" osb - it's so flimsy it won't add much unless it's completely bonded to the lower layer, which it won't be.

    Having said that, what seems like a minor issue isn't.  If your stairs are cut correctly you'll spend two or three times as much shimming everything so your rises work out correctly - EACH riser and tread will need to be shimed and no two risers will be shimmed the same amount.  Havng to screw with every door opening in the house will double the door install times.  In the end you've made more work for yourself.

    However, a double layer of 3/4" osb glued and screwed is super stiff - ideal really.

  7. calvin | Jul 09, 2013 07:20am | #15

    Larry

    Most new construction is rained on and most problems with OSB are at the joints/seams.

    Get a floor sander and hit those expanded edges to even it out and be done.  Adding to the top will only "cover" whats there.  Minor flaking shouldn't be a problem with carpet pad or thin underlays.  Then there's no complications with stairs and entries.

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

FHB Podcast Segment: Efficient HVAC for a New Build

Self-installing an HVAC system requires a lot of thought and planning.

Featured Video

How to Install Exterior Window Trim

Learn how to measure, cut, and build window casing made of cellular PVC, solid wood, poly-ash boards, or any common molding material. Plus, get tips for a clean and solid installation.

Related Stories

  • Podcast Episode 686: Brick Steps, Ground-Source Heat Pumps, and Greenhouses in Nova Scotia
  • FHB Podcast Segment: Efficient HVAC for a New Build
  • Affordable Scans, Accurate Plans
  • FHB Summit 2025 — Design, Build, Business

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

Fine Homebuilding Magazine

  • 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
  • Issue 327 - November 2024
    • Repairing Damaged Walls and Ceilings
    • Plumbing Protection
    • Talking Shop

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

Enjoy unlimited access to Fine Homebuilding. Join Now

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