Span Chart

[Nick Ostrowski]

Does anybody have a span chart for dimensional lumber? I looked at a house today with measured 1.5"x9 inch ceiling joists for the 1st floor. The joists were spaced 16" oc and were spanned 13'. The floor had a lot of squeaking but nothing I would necessarily in and of itself consider a defect.

[Jerry Peck]

Does anybody have a span chart for dimensional lumber? I looked at a house today with measured 1.5"x9 inch ceiling joists for the 1st floor. The joists were spaced 16" oc and were spanned 13'.


Sounds like 2x10 (1-1/2" x 9-1/4"), 16" o.c., and is the 13' from edge-of-bearing to edge-of-bearing?

Finally, and quite importantly, would be the species of wood the joists are.

[Nick Ostrowski]

Yes Jerry. 13' from edge of bearing to edge of bearing.

Species of wood? No clue.

Two thirds of the 1st floor ceiling joists were spaced at 12" oc with similar spans. For some reason, the builders framed the other 1/3 at 16 oc. Maybe they ran out of money.

[Jerry Peck]

From Table R503.3.1(1) Residential sleeping areas
- Joist Spacing 12" - 2 x 10 - Spruce-Pine-Fir #3 (worst case/shortest allowed) - 20 psf - 13'5" span
- Joist Spacing 16" - 2 x 10 - Spruce-Pine-Fir #3 (worst case/shortest allowed) - 20 psf - 11'8" span

- Joist Spacing 12" - 2 x 10 - Douglas fir-larch SS (best case/longest allowed) - 20 psf - 21'0" span
- Joist Spacing 16" - 2 x 10 - Douglas fir-larch SS (best case/longest allowed) - 20 psf - 19'1" span

From Table R503.3.1(2) Residential living areas
- Joist Spacing 12" - 2 x 10 - Spruce-Pine-Fir #3 (worst case/shortest allowed) - 20 psf - 12'3" span
- Joist Spacing 16" - 2 x 10 - Spruce-Pine-Fir #3 (worst case/shortest allowed) - 20 psf - 10'7" span

- Joist Spacing 12" - 2 x 10 - Douglas fir-larch SS (best case/longest allowed) - 20 psf - 19'1" span
- Joist Spacing 16" - 2 x 10 - Douglas fir-larch SS (best case/longest allowed) - 20 psf - 17'4" span

You can see why species (and grade) are needed to make an informed decision on what might be okay.

[Jerry Peck]

For some reason, the builders framed the other 1/3 at 16 oc. Maybe they ran out of money.


Or maybe they planned for something heavy under part of it for the original owners, such as a grand piano or who-knows-what (if anything)??

[Michael Garrity]

I have the same figures only at 10psf not 20psf. 2007 NYS R502.3.1

Let me revise that. NYS code is the same as JP's post.10psf would be the sleeping area and 20psf would be the living area and are under the one table.[residential living areas}

[Steve Frederickson]

A VERY ROUGH rule of thumb is that the allowable span in feet is 1.5 times the depth of the joist in inches: for example, 2x8=12' span, 2x10=15' span, etc. Obviously, the species and grade of lumber, the joist spacing, the loading, the allowed deflection, etc. all need to be known to make a final determination, but the rule-of-thumb is handy to decide if you should look a little closer

[Matt Fellman]

This topic, as it pertains to home inspections, always catches my interest. Having taken several years of civil engineering, and just building various things, I know my way around span tables very well.

But..... at what point do we as HIs cross the line and open ourselves up to be accused of undertaking actual "engineering" ?

I personally won't go very far down this path during the course of a home inspection. Sure, I may come home and look something up on a span table but I'd never, never, never cite my source for saying it's inadequate.

I seem to remember hearing (probably around here) a story or two of HIs getting their hands slapped for playing engineer.

To me this is always a funny crossroad between our SOPs and what is reality. Basically, SOPs all say something about just observing and making sure everything looks good. Then, they go on to say the inspection is not technically exhaustive and you aren't required/allowed, etc. to undertake any engineering.

How can you really do the first without doing the second?

[Darren Miller]

Nick

If you took pictures, it's possible the grade stamp is visible. Check it out.

[Brandon Whitmore]

To me this is always a funny crossroad between our SOPs and what is reality. Basically, SOPs all say something about just observing and making sure everything looks good. Then, they go on to say the inspection is not technically exhaustive and you aren't required/allowed, etc. to undertake any engineering.

Hi Matt,

I guess I've never really worried about it. I don't consider myself doing any engineering work when I cite a code source showing readily available span tables. I'm just citing my source for concern. Of course, I usually start looking at span charts when I see something sagging, feels springy, etc. -- then I can write up the issue, and show the span chart backing up my concern.
I've had several lawsuit threats from the selling side over the years, but nobody has followed through-- time will tell if I'm going too far I guess.

[Bruce King]

From Table R503.3.1(1) Residential sleeping areas
- Joist Spacing 12" - 2 x 10 - Spruce-Pine-Fir #3 (worst case/shortest allowed) - 20 psf - 13'5" span
- Joist Spacing 16" - 2 x 10 - Spruce-Pine-Fir #3 (worst case/shortest allowed) - 20 psf - 11'8" span

- Joist Spacing 12" - 2 x 10 - Douglas fir-larch SS (best case/longest allowed) - 20 psf - 21'0" span
- Joist Spacing 16" - 2 x 10 - Douglas fir-larch SS (best case/longest allowed) - 20 psf - 19'1" span

From Table R503.3.1(2) Residential living areas
- Joist Spacing 12" - 2 x 10 - Spruce-Pine-Fir #3 (worst case/shortest allowed) - 20 psf - 12'3" span
- Joist Spacing 12" - 2 x 10 - Spruce-Pine-Fir #3 (worst case/shortest allowed) - 20 psf - 10'7" span

- Joist Spacing 12" - 2 x 10 - Douglas fir-larch SS (best case/longest allowed) - 20 psf - 19'1" span
- Joist Spacing 16" - 2 x 10 - Douglas fir-larch SS (best case/longest allowed) - 20 psf - 17'4" span

You can see why species (and grade) are needed to make an informed decision on what might be okay.


Jerry, there is a typo for one line in the living area section where you have 12", it should be 16". Was this copied and pasted from the code?

[Markus Keller]

I haven't seen 2x10 pass Muni insp or Permit App here over 12'. 2x12 will pass up to about 15,16'. Beyond that it's truss, microlam, etc.
On older existing house I see it all the time but not on new. On old I don't comment on it, on new I would report it and recommend checking compliance.

[Jim Luttrall]

Citing span tables in the model building code is NOT engineering.
You can follow the prescriptive or model code or have an engineer design a building.
Citing a framing member as exceeding the allowable span in the IRC is no different than citing an over fused circuit or a missing GFCI. Not designing, just reporting.


From Wikipedia

Engineering is the discipline, art and profession of acquiring and applying technical, scientific, and mathematical knowledge to design and implement materials, structures, machines, devices, systems, and processes (http://en.wikipedia.org/wiki/Process_%28engineering%29) that safely realize a desired objective or invention.

[Jerry Peck]

Jerry, there is a typo for one line in the living area section where you have 12", it should be 16".

You are correct - I went back and corrected it.


Was this copied and pasted from the code?

Unfortunately the table was too complex to copy and paste, so I had to type it out .. and typed it out with a typo. :o

The lines were supposed to alternate 12" and 16".

[Andrew Christel]

Try this site. Nick





Lumber Talk.com: Professional-Level information and how-to-build articles for wood, timber, and lumber professionals and users. Span Tables » Lumber Talk (http://www.lumbertalk.com/2007/12/07/span-tables/)

[Steve Frederickson]

Or, try this: http://www.awc.org/pdf/STJR_2005.pdf

[Michael Chambers]

................Unfortunately the table was too complex to copy and paste, so I had to type it out .. and typed it out with a typo. :o ................
You mite have the same probrem I habe. My keybord can't spel wurth a darn ether! I neeed to replac it! :D

[rog_arch]

When there is no stamp visible what Fb should be assumed?