Span charts/calculator for 4x lumber
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woodwrights_corner
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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.
woodwrights_corner
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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
Sincerely, good luck
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.
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
...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
woodwrights_corner
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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
http://build.decksgo.com/calculators/beam-span-calculator.php
ctvader said:
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 likehttps://www.awc.org/codes-standards/calculators-software/spancalc
GoingMyWay
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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.
Paul G said:
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.
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
DeformedTree
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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.
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.
Hurricane Whisperer
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Paul G said:
I've been wondering the same thing. Why do you want 4x for joists?
Hurricane Whisperer said:
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.
Hurricane Whisperer
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Paul G said:
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.
Paul G said:
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/
