Author Topic: Span charts/calculator for 4x lumber  (Read 1940 times)

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Offline Paul G

  • Posts: 1977
Span charts/calculator for 4x lumber
« on: April 09, 2019, 12:32 AM »
I’ve been looking but can’t find any span charts or calculators that include 4x lumber for rafters or joists, has anyone come across such info? I know it is unusual but would be useful at times for odd situations. Any help is appreciated.
+1

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Offline woodwrights_corner

  • Posts: 72
Re: Span charts/calculator for 4x lumber
« Reply #1 on: April 09, 2019, 10:59 AM »
For what it's worth I used your subject line and did a web search.  Web search turned up a few sights that showed span charts/calculator for decks.  These calculators were for different types of woods and 2x sizes "sistered" (sp).  There was nothing on true 4x4's that I found.  I could not find any notes/dates on these sites that said they included the recent updates in their calculator.  Not much, but maybe it helps a little.

Offline Paul G

  • Posts: 1977
Re: Span charts/calculator for 4x lumber
« Reply #2 on: April 09, 2019, 01:01 PM »
For what it's worth I used your subject line and did a web search.  Web search turned up a few sights that showed span charts/calculator for decks.  These calculators were for different types of woods and 2x sizes "sistered" (sp).  There was nothing on true 4x4's that I found.  I could not find any notes/dates on these sites that said they included the recent updates in their calculator.  Not much, but maybe it helps a little.

You have better search skills than I, haven’t seen a chart or calculator that included data for sistered joists. If you can post a link here it would be much appreciated.
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Offline woodwrights_corner

  • Posts: 72
Re: Span charts/calculator for 4x lumber
« Reply #3 on: April 09, 2019, 02:29 PM »
Sorry,  I'm kind of the same age as Mr. Tinker, but he is much wiser than I.  I can search but cannot link.  If you search ye shall find..

Sincerely, good luck

Offline Paul G

  • Posts: 1977
Re: Span charts/calculator for 4x lumber
« Reply #4 on: April 09, 2019, 04:22 PM »
Well as I said in my first words, I’ve been looking... for quite some time and haven’t seen a single chart or calculator that lists spans for sistered 2x joists let alone 4x lumber. I’ve come across several discussions by people like myself looking for the same but no resolution. The calculators are very helpful in general but the ones I’ve found online or as apps only have 2x lumber for joists with no selections for sistering. You say it’s out there and I have no reason to not believe you but I haven’t yet seen it. If you ever sort out how to post a link it would be appreciated.
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Offline dupe

  • Posts: 75
Re: Span charts/calculator for 4x lumber
« Reply #5 on: April 09, 2019, 04:55 PM »
A rule of thumb for estimating is (2x) joist depth : span/16
...wood beam : span/15, beam width = 1/3 to 1/2 beam depth    REF: Ching, building construction illustrated

As for tables...
I'm assuming southern yellow pine. Header and Beam : Size Selection Tables

Here is the table for Joist and Rafters.

In order to use these tables you will need the prescribed dead load (DL) and live load (LL). This may not be relevant to your area or meet code requirements, but as an example:
A 3 story house in Louisiana
-Ground Floor = DL 50/ LL 40 (psf)
-First Floor = DL 10/ LL 40 (psf)
-Second Floor = DL 10/ LL 30 (psf)
-Roof = DL 15/LL 20 (psf)

Hope this helps, but consult and engineer or over engineer
MFT.1080    CT.Midi    DF.500    DTS.400    ETS.EC150/3    RO.150    RO.90    CXS 10.8

Offline woodwrights_corner

  • Posts: 72
Re: Span charts/calculator for 4x lumber
« Reply #6 on: April 09, 2019, 05:08 PM »
Try this.  Not exactly what you want and I don't know if it is up to date.

http://build.decksgo.com/calculators/beam-span-calculator.php

Offline ctvader

  • Posts: 57
Re: Span charts/calculator for 4x lumber
« Reply #7 on: April 10, 2019, 07:48 AM »
What about calling a lumber yard and asking their advice or your local building department. They may be able to point you in the correct direction.

Offline Paul G

  • Posts: 1977
Re: Span charts/calculator for 4x lumber
« Reply #8 on: April 10, 2019, 09:25 AM »
A rule of thumb for estimating is (2x) joist depth : span/16
...wood beam : span/15, beam width = 1/3 to 1/2 beam depth    REF: Ching, building construction illustrated

As for tables...
I'm assuming southern yellow pine. Header and Beam : Size Selection Tables

Here is the table for Joist and Rafters.

In order to use these tables you will need the prescribed dead load (DL) and live load (LL). This may not be relevant to your area or meet code requirements, but as an example:
A 3 story house in Louisiana
-Ground Floor = DL 50/ LL 40 (psf)
-First Floor = DL 10/ LL 40 (psf)
-Second Floor = DL 10/ LL 30 (psf)
-Roof = DL 15/LL 20 (psf)

Hope this helps, but consult and engineer or over engineer

Yes, I've been to the southern pine website, lots of great info there but unfortunately nothing I could find there about using 4x lumber for joists.
+1

Offline Paul G

  • Posts: 1977
Re: Span charts/calculator for 4x lumber
« Reply #9 on: April 10, 2019, 09:27 AM »
Try this.  Not exactly what you want and I don't know if it is up to date.

http://build.decksgo.com/calculators/beam-span-calculator.php

yup, been to that one also, but unfortunately nothing there either about using 4x lumber for the joists.
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Offline Paul G

  • Posts: 1977
Re: Span charts/calculator for 4x lumber
« Reply #10 on: April 10, 2019, 09:36 AM »
What about calling a lumber yard and asking their advice or your local building department. They may be able to point you in the correct direction.

Talked with a local lumber yard, the basic answer I got was 'why would you want to use 4x for joists?' and no further info since it is out of the norm. The local bldg dept actually had something but only related to making a patio cover, better than nothing but not the same detail as we see in span calculators like https://www.awc.org/codes-standards/calculators-software/spancalc
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Offline GoingMyWay

  • Posts: 779
Re: Span charts/calculator for 4x lumber
« Reply #11 on: April 10, 2019, 10:12 AM »
I did a quick Google image search and found a table on this website: https://www.hometips.com/buying-guides/maximum-beam-rafter-spans.html showing maximum beam spans.  It sounds like it might be similar (if not maybe the same thing that your building department gave you) in that it's not really detailed and it's also for a patio roof.
Inquiring Minds Want to Know

TS55, CT26, RO150, CXS, ETS 150/3, ETS EC 150/5, MFT/3, TS75, DF500, DTS400, OF1400, CT SYS

Offline dupe

  • Posts: 75
Re: Span charts/calculator for 4x lumber
« Reply #12 on: April 10, 2019, 04:13 PM »
Well as I said in my first words, I’ve been looking... for quite some time and haven’t seen a single chart or calculator that lists spans for sistered 2x joists let alone 4x lumber. I’ve come across several discussions by people like myself looking for the same but no resolution. The calculators are very helpful in general but the ones I’ve found online or as apps only have 2x lumber for joists with no selections for sistering. You say it’s out there and I have no reason to not believe you but I haven’t yet seen it. If you ever sort out how to post a link it would be appreciated.

All the tables for Headers and Beams have clear span for sistered or built-up beams. From the same book referenced above, "Built-Up Beam: Equal in strength to the sum of the strengths of the individual pieces if none of the lamination are spliced. *Nailed w/ 10d @ 16" oc staggaered with two 10d @ each end." I would take this info and short the span slightly for your application (assuming built up beam has opposing or altering grain i.e. added strength) or elaborate on what you're trying to do. I wouldn't span 24' clear at 24" o.c.
MFT.1080    CT.Midi    DF.500    DTS.400    ETS.EC150/3    RO.150    RO.90    CXS 10.8

Offline Don T

  • Posts: 1879
  • Phoenix, Az
Re: Span charts/calculator for 4x lumber
« Reply #13 on: April 10, 2019, 04:23 PM »
Here is another link you may want to look at for maximum span.
RO150, C12, DF 500 Q, CT33, TS75, MFT3, Kapex 120, MFT3/Kapex, MFK 700, RO 90, ETS150/3, CT22, Centrotec Installers Kit, Parallel Guides & Ext, Carvex, OF1400, LR32 Set, MFS400 w/700 rails, KA UG Set, First Aid Kit, RTS 400 EQ, Vecturo OS400 Set, CT Wings, CT Drill Guide, Pro 5, CXS, C18, HL850, Vac Sys set

Offline Paul G

  • Posts: 1977
Re: Span charts/calculator for 4x lumber
« Reply #14 on: April 10, 2019, 08:06 PM »
I started doing timber frame construction searches and found these calculators where you can enter in your own lumber dimensions instead of only stuff from a pull down list. This is getting somewhere, here's a link if it will help anyone else.  http://forestryforum.com/members/donp/beamindex.htm
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Offline DeformedTree

  • Posts: 467
Re: Span charts/calculator for 4x lumber
« Reply #15 on: April 10, 2019, 09:41 PM »
So in IRC 2015, most tables for headers and such have a note below them saying to can interpolate for values between those listed.

There is an interesting table for deck beam spans.   Table R507.6

it has a few rows that call out   3x6 or 2 -2x6,  3x10 or 2 - 2x10, etc.    It list the same span values for the solid verses the build up.  Now I would assume a 3x6 to be 2.5" thick vs 2  2byes which would be 3", so maybe some conservative nature.  So that is one place that touches on this.  The conservative nature makes sense both from simplicity but also when laminating multiple members you have a lower statistical chance of a bad flaw being in the same spot of the beam (one board could have a crack, the other doesn't vs one crack thru it all).  Engineered beams take this to an extreme and thus why something of the same dimensions has much higher ratings, they know what they got in that beam, so you can't use their numbers and apply to a sawn beam.

I would direct you to local building department.  Also if these are sawn beams with no stampings on them, now that's a whole other issue.

I think regular code doesn't list them because it's cover light wood framing, not heavy timber framing (post and beam).  I don't know what code covers post and beam construction, but that's probably where you need to head.

Re: Span charts/calculator for 4x lumber
« Reply #16 on: April 22, 2019, 10:43 PM »
What about calling a lumber yard and asking their advice or your local building department. They may be able to point you in the correct direction.

Talked with a local lumber yard, the basic answer I got was 'why would you want to use 4x for joists?' and no further info since it is out of the norm. The local bldg dept actually had something but only related to making a patio cover, better than nothing but not the same detail as we see in span calculators like https://www.awc.org/codes-standards/calculators-software/spancalc

I've been wondering the same thing.  Why do you want 4x for joists?

Offline Paul G

  • Posts: 1977
Re: Span charts/calculator for 4x lumber
« Reply #17 on: April 23, 2019, 12:23 AM »
I've been wondering the same thing.  Why do you want 4x for joists?

There’s odd times where there is a lack of space for the typical 2x applications, say where a 2x8 would be the norm, but with insufficient room for it perhaps a 4x6 may work. A span chart for 4x materials could answer the question with more certainty.
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Re: Span charts/calculator for 4x lumber
« Reply #18 on: April 23, 2019, 08:43 PM »
I've been wondering the same thing.  Why do you want 4x for joists?

There’s odd times where there is a lack of space for the typical 2x applications, say where a 2x8 would be the norm, but with insufficient room for it perhaps a 4x6 may work. A span chart for 4x materials could answer the question with more certainty.

The following is posted soley in service to public safety.

Dupe posted important information relating to allowable spans for various sizes of standard 2x lumber.  Others posted useful advice.  The lumber yard you called asked a very pertinent question.  The various organizations providing span tables for 2x construction did so for well thought out and time honored reasons.

Basically, if a floor joist is determined to be inadequate to support a given load at a given span, then you must either reduce the span to a safe one for the desired floor joist size, reduce the spacing between floor joists to a lesser but still practical standard spacing, or go to a larger 2x lumber size of sufficient width to safely support the load at the required span under the given load.

If your solution is to go to 4x lumber to attempt to fix the problem of an inadequate floor joist, then you probably need to step back and reevaluate your design or question your understanding of the concept of moment of inertia as it relates to supporting floor loads.

2x lumber works well for standard construction techniques, including the ability to fasten it in a structurally sound method as well as being able to handle it and fabricate with it using common tools.

If you examine the tables provided by Dupe, you will determine that going up to the next size 2x increases allowable span much more than use the same 2x at the next closer standard spacing.  This is due to the increase in the moment of inertia by an extra 2 inches of nominal width size. 

In constructing a deck, I think it would be highly unlikely that going to 4x lumber for floor joists would make any sense at all rather than following conventional construction practice that meets applicable codes and industry standard construction practices.
« Last Edit: April 23, 2019, 08:45 PM by Hurricane Whisperer »

Offline harry_

  • Posts: 1264
Re: Span charts/calculator for 4x lumber
« Reply #19 on: April 23, 2019, 08:51 PM »
I've been wondering the same thing.  Why do you want 4x for joists?

There’s odd times where there is a lack of space for the typical 2x applications, say where a 2x8 would be the norm, but with insufficient room for it perhaps a 4x6 may work. A span chart for 4x materials could answer the question with more certainty.

It has always been my understanding that a 4X of a given width offers less strength than a pair of 2x of the same width.

If joist height room is an issue, then you should consider using either LVL or TGI if in interior spaces or a making a 'flitch' if the weather can get at it. If going flitch route you'll be doubling the 2x lumber regardless.

http://www.strucalc.com/tag/flitch-beam/
« Last Edit: April 23, 2019, 08:54 PM by harry_ »
Disclaimer: This post is for educational and entertainment purposes only. Any resemblance to real persons, living or dead is purely coincidental. Void where prohibited. Some assembly required. Batteries not included. Contents may settle during shipment. Use only as directed. No other warranty expressed or implied. This is not an offer to sell securities. May be too intense for some viewers. No user-serviceable parts inside. Subject to change without notice. One size fits all (very poorly).

Offline DeformedTree

  • Posts: 467
Re: Span charts/calculator for 4x lumber
« Reply #20 on: April 23, 2019, 10:19 PM »
I've been wondering the same thing.  Why do you want 4x for joists?

There’s odd times where there is a lack of space for the typical 2x applications, say where a 2x8 would be the norm, but with insufficient room for it perhaps a 4x6 may work. A span chart for 4x materials could answer the question with more certainty.

It has always been my understanding that a 4X of a given width offers less strength than a pair of 2x of the same width.


This is what I touched on above. It's not so much that it couldn't be stronger or as strong, it's just the issue that wood is a natural product with flaws. Using multiple timbers reduces the risk of flaws (not as likely to fall in the same spot).  Engineered wood takes this to the extreme and thus gets higher ratings.

Look at old multi member beams. Very normal for one of the 2x's to have sagged more than others.  Had this been 1 timber instead of multiple, you could have had the timber cut from the same tree that sagged more than the others and now the whole beam sagged/failed.

This is where timber frame construction makes me nervous (even if beautiful).  You have a fracture critical structure as you no longer have the benefit of statistics in the framing.

I get if the idea behind wanting to use 4x lumber was looks, sure it looks much nicer than laminating 2x's, but it can present issues.

Offline Paul G

  • Posts: 1977
Re: Span charts/calculator for 4x lumber
« Reply #21 on: April 24, 2019, 12:14 AM »
Hurricane Whisperer, I agree with your comments. That’s why actual charts or calculators are so helpful, providing real numbers instead of rules of thumb.
+1

Offline Paul G

  • Posts: 1977
Re: Span charts/calculator for 4x lumber
« Reply #22 on: April 24, 2019, 12:20 AM »

If joist height room is an issue, then you should consider using either LVL or TGI if in interior spaces or a making a 'flitch' if the weather can get at it. If going flitch route you'll be doubling the 2x lumber regardless.

http://www.strucalc.com/tag/flitch-beam/

Yes, engineered products can be an option.
+1

Re: Span charts/calculator for 4x lumber
« Reply #23 on: April 24, 2019, 12:34 AM »
Hurricane Whisperer, I agree with your comments. That’s why actual charts or calculators are so helpful, providing real numbers instead of rules of thumb.

I think if you understood the comments, then you wouldn't be asking for 4x floor joist charts.  Deformed Tree added yet another reason why 2x lumber is used even if doubled up to make a 4x header or other part of the structure.

Offline Paul G

  • Posts: 1977
Re: Span charts/calculator for 4x lumber
« Reply #24 on: April 24, 2019, 10:29 AM »
Hurricane Whisperer, I agree with your comments. That’s why actual charts or calculators are so helpful, providing real numbers instead of rules of thumb.

I think if you understood the comments, then you wouldn't be asking for 4x floor joist charts.  Deformed Tree added yet another reason why 2x lumber is used even if doubled up to make a 4x header or other part of the structure.

Here is what I hope we can all agree on, all other things being equal, a 4x8 will hold more load than a 2x8. The charts or calculator helps a non-engineer know how much so. I understand sistering is probably even better (depends on how those pieces are joined), adding steel into the mix even better. And I understand it isn’t in the norm of current practices. It was just a simple request for data that I couldn’t find, no need to make more out of it than there is.
+1

Offline Cheese

  • Posts: 5920
Re: Span charts/calculator for 4x lumber
« Reply #25 on: April 24, 2019, 11:06 AM »
I'll routinely use aluminum flats if I need additional strength without the thickness.

Here's a 3/4" or 1" thick aluminum flat sanded on the rear surface to remove the oxide coating and to add some tooth.

Fastened to it's own aluminum base, top & bottom.

Adhered to the existing 2x material with PL 400.

Secured to the 2x material with #12 construction screws.