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

glue lam laid flat july 2001 FHB #140

ponytl | Posted in General Discussion on January 18, 2003 07:08am

In the july 2001 FHB there is a house built by Glen Irani…  where he uses 3 1/8 glue lams laid flat supported on steel i-beams for a loft/second floor area…  I’m doing a project where we need to build a loft area and keep as much headroom up & down as we can and still split a floor… what i need to know is…

what kind of span and loads can i get out of a laid flat 12” wide glue-lam?…

each loft will be aprox 16′ wide and 20′ deep…  i have a brick wall at one 16′ end and a cross beam at 15’… would these span 5′ … 7.5′ ? anyone have a clue on where i could find out

thanks in advance

Craig  [email protected]

Reply

Replies

  1. FrankB89 | Jan 18, 2003 11:00pm | #1

    I'm not real clear with how you've described your spans.  If you're spans are only "5'...7.5,'"  my gut tells me you're probably OK, but bear in mind that a glue lam is designed to function in vertical cross section.  If your span is getting out there in the 12' + area. you'd be advised to get the blessing of a PE (professional engineer).

    There was a thread sometime back, early last summer maybe, about someone who, like you, was trying to maximize headroom and there was a discussion about a diaphram-type construction, kind of on the boxbeam concept, using plywood surfaces glued and screwed to a wood structural web.  As I recall, there was some positive feedback on it.

    Maybe somebody with a better memory than me will jump in here and point you in that direction.

    Jules Quaver for President   2004

    1. ponytl | Jan 18, 2003 11:23pm | #2

      basicly it's a 15' x 20' loft area (9 of em) i have a brick wall at the back for a ledger... then i have 8x8 posts going to the roof 15' out from the wall...  i can put a load bearing beam across the posts for one support... (i hope a 8" I-beam)  but between the back wall and the post... try'n to find out do i need one more I-beam (7.5ft span  or 2 for a 5' span... then catilever the forward most 5' past the beam attached to the 8x8 posts...  cost wise since i end up with a floor & ceiling basicly ready for finish it works out pretty well... (about $1350.00 per loft for glue-lams)...  thanks for your input...

      oh yeah... thought i'd put a 1/4" edge grove in em and spline em.. predrill the i'beam and mechanical fasten em from the bottom... leave em off the side walls with a 3/8" foam gasket and run my trim top & bottom....

      Edited 1/18/2003 3:39:03 PM ET by ponytl

  2. User avater
    BossHog | Jan 18, 2003 11:26pm | #3

    If the glulam is laid flat, it doesn't really have any more strength than a few 2X4s laid next to each other.

    There are some SYP span charts here:

    http://www.southernpine.com/tables/2.htm

    Unfortunately they don't cover 2X4. You might look at getting some high grade 2X4 from a truss plant, and using them as conventional floor joists. It would sure be cheaper that using glulams.

    Snowmobiles: Natural selection at its finest.

    1. UncleDunc | Jan 19, 2003 01:20am | #4

      >> If the glulam is laid flat, it doesn't really have any more strength than

      >> a few 2X4s laid next to each other.

      Slightly less, actually, because it's not even as thick as a 2x4 is wide. A board 1-1/2" x 3-1/8" with the 3-1/8" dimension vertical will have 42% of the strength of a 2x8, and 7% of the stiffness, all else being equal. 10.7 of them glued together for a width of 16" will have 444% of the strength and 78% of the stiffness of a 2x8.

      As Boss has pointed out before, even if 78% of the stiffness of a 2x8 is enough to meet the deflection limits of your situation, the floor may still feel bouncy if the resonant frequency of the whole floor assembly is too low. Your span may be short enough that that won't be a problem.

      1. jimblodgett | Jan 19, 2003 03:37am | #5

        I sure hope some engineer chimes in here, but I think there is great strength in a glulam layed over on it's side - way more than the same number of 2x4's nailed together would have, and WAY more than simply multiplying the individual span strength times the number of boards.

        As I understand it, horizontal structural member most often fail when the center rolls over towards horizontal, even if the two ends are secured upright.  You've probably seen this many times, where the middle section of an overloaded ceiling joist starts to lean, or twist.  (came back to say that that's why midspan blocking and cross bridging strengthen a span, because they keep the middle of those framing members from rolling under load)

        So my thinking would be, that the glulam is alot stronger because there no way for those individual 2xs to roll, and I am having a real tough time imagining the entire beam rolling into what would be vertical. 

        In fact, I think I remember a friend telling me he was renovating some turn of the century flat roofed commercial buildings in Tacoma, and that's exactly how the roofs were were framed, 2x4s on edge, nailed together across the entire width of the building.

        Now as for that ledger on a brick wall, I think you might have some problems there.  At least if you are working in any type of siesmic sensitive area.  I'd be interested to hear how you intend to do that.

        Edited 1/18/2003 7:39:33 PM ET by jim blodgett

        1. UncleDunc | Jan 19, 2003 04:22am | #6

          >> ... and WAY more than simply multiplying the individual span strength

          >> times the number of boards.

          Why do you believe that? If you double the width of a beam, you double the strength and stiffness. If you make a 3-1/2" x 15" glulam by gluing 10 2x4's together and then lay it on its side, it is exactly 10 times as strong and 10 times as stiff as one 2x4 in the same orientation.

          1. donpapenburg | Jan 19, 2003 07:43am | #10

            I have to side with Jimbo on this one . A 2x4 sistered will be stronger , but if you use some good glue and then glue 10 together the srength will be greater then 10 sitting against one another. now If I read his post he wants to fill his whole opening with g,lam one abutting the other and glued together should make for a very stought floor . If that is not srong enough try the 2x6 g,lam

          2. jimblodgett | Jan 19, 2003 09:40am | #11

            Uncle Dunc - you said, ">> ... and WAY more than simply multiplying the individual span strength >> times the number of boards.

            Why do you believe that?"

            Let's see if I can say this...first off, the thing I said earlier about the way a horizontal framing member fails, by rolling.

            But there's more.  And I can't cite any engineering background or facts here, Dunc, but I'll try my best to explain my thinking. 

            Let's say a 2x4 spanning 8 feet is rated to carry x number of psf.  Okay, tests have been performed under controlled conditions and the data studied by qualified people to get that rating, right?

            So we all know that there will be parts of that 2x4 that are weak points, like at a dead knot, or where the grain runs off the edge of the board, right?  But all that gets factored in and an average is calculated of many tests to come up with the expected strength of the average 2x4 of any given grade.

            If you sister two 2x4's together, the weak points in one stick are unlikely to be aligned with the weak points in the other - so two would carry more than twice the amount of one, three more than three times and so on. 

            I don't know, it just seems right.  Do you think I'm basing this on a faulty premise?  

            Edited 1/19/2003 1:45:17 AM ET by jim blodgett

          3. UncleDunc | Jan 19, 2003 01:41pm | #12

            I can see the sense of that. My calculations were based on the theoretical behavior of beams, assuming that wood is perfectly uniform, like steel. Which it's not.

            However, I don't think it would be a good idea to _depend_ on getting a more than linear increase in strength or stiffness as a basis for design decisions. If your design depends on getting 210% of the stiffness a single joist by gluing two of them together, what happens if you get two that do have their weak spot in the same place?

          4. User avater
            BossHog | Jan 19, 2003 03:15pm | #13

            "If you sister two 2x4's together, the weak points in one stick are unlikely to be aligned with the weak points in the other - so two would carry more than twice the amount of one, three more than three times and so on."

            That's basically true. The NDS allows you to take a 15% increase in the bending value for lumber that's sheated with plywood, if there are 3 or more in a row and less than 24" O.C. This applies to most residential framing.Prevent death on the road. Drive on the sidewalk

          5. donpapenburg | Jan 19, 2003 06:33pm | #14

            Remember you are talking 2xs with a space between them and sheeted with ply they still have room to roll. Now if they are glued to each other ,effectivly making them wider than tall they'll tend not to roll.

            I would feel safer on a gluelam of 2x3s 10"laid flat than on a 3x10 laid flat spanning that space. I t would be like the scafold planks that Jim made up out of 2x and ply . Stout enough for aunt Tilly and her keg of beer.

            By the way Jim I made up acouple of those planks .Work great !

        2. User avater
          BossHog | Jan 19, 2003 05:53am | #7

          You're partly right, I think.

          Using a Glulam would keep them from rolling if they were maxed out. But so would plywood glued and nailed on top of conventional floor joists.Diagonally parked in a parallel universe.

  3. PTurtiak | Jan 19, 2003 06:43am | #8

    The companies that make gluelam beams will make you a beam any width and height you want.  They will also size them for you, so don't settle on the product that is available at your local lumber yard when you can special order the beam you need.

    Parallam beams can also be special ordered in any size. 

    1. User avater
      NannyGee | Jan 19, 2003 07:29am | #9

      I can't give you engineering, but I saw a TOH episode on a scandinavian townhome development where they did this on all the floors. I think the max span was 12'.

      I would have absolutely no concern about failure - you could park a car on it - but I would wonder about shrinkage and expantion from season to season. Seems to me a 15' wide sheet of pine could easily move 2'' or more back & forth.

      1. ponytl | Jan 19, 2003 11:02pm | #15

        This is an old produce warehouse in memphis on the mississippi river I have enough ceiling height to split the floors (just under 17') as long as i keep the floor as slim as i can...  and can you guys say "cheap"  it's not that I am...  it's what i have to be...  it's a warehouse... and i can use cheap materials...  polished/cut concrete floors, no 2 units have to be the same (20 of em) so I scrounge materials... buy overruns overstocks... ect...

        I'm not sure on the movement of 15   3 1/8 x 12x 20' glue-lams laid side x side and i'm in the hope that i can get a 90" span out of them...( if i have to go to 60" i can, it just adds to my already strapped budget) it's a sleeping loft  with a bathroom (shower no tub) so it won't be high loads (no waterbeds i hope)... 

        what do you guys thing about spline'n em maybe 1/2' deep x 1/4  cut on each butting side with 7/8 x 1/4  spline....  that'd be 3000 or so ft of routing... so would it be worth it?

        1. FrankB89 | Jan 19, 2003 11:27pm | #16

          90" span?  I wouldn't bother with a spline.  After all the input here, it seems you're going to have a pretty firm floor.  To join the beams you could dowel them if you care to on about 2' centers...table leaf effect.  No science here, just a thought.  But if they're firmly attached to bearing surfaces below, they're probably not going anywhere.  Lams are made of kiln-dried wood after all.Jules Quaver for President   2004

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

A Classic Paint Sprayer Gets a Thoughtful Refresh

The Titan Impact X 440 offers great coverage with minimal overspray.

Featured Video

Builder’s Advocate: An Interview With Viewrail

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

Related Stories

  • Podcast Episode 693: Old-House Hazards, Building Larsen Trusses, AI in Construction
  • FHB Podcast Segment: Finding Hazardous Materials in a Fixer-Upper
  • A Classic Paint Sprayer Gets a Thoughtful Refresh
  • Podcast Episode 692: Introduction to Trade Work, Embodied Carbon, and Envelope Improvements

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 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