At a 6' span, how much can an SPF 2x4 turned on 3.5" end support?

Question

The ends are secured, so how much load can a 6' span of SPF 2x4 support when turned on 3.5"?

It depends on the loading distribution. Point loading? Evenly distributed across the span? — Doresoom, Apr 02 '12 at 21:30
Also, the modulus of rupture varies widely both with wood species and moisture content. — Doresoom, Apr 02 '12 at 21:41

score 8 · Answer 1 · answered Apr 03 '12 at 16:07

8

The Sagulator says it will support about 375 pounds (evenly distributed) before there is noticeable deflection. I recommend you go to the site, read the notes, and play around with the numbers yourself.

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answered Apr 03 '12 at 16:07

mwolfe02

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Note that while this is a good resource, it won't tell you when the beam will actually break. Try replacing 375 lbs total with 90000 lbs/ft. The calculator gives a sag of nearly 29" per foot, which is obviously impossible. – Doresoom Apr 03 '12 at 17:16
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Good point. The "Sagulator" is really geared more toward shelving, whereas the span tables that shirlock referenced are geared more toward structural engineering. It's not entirely clear from the question what the OP's intent is here. – mwolfe02 Apr 03 '12 at 19:16
my only question about this answer is why center load was not selected in the screenshot. @doresoom and mwolfe02 a footnote in the tool reads "Target sag: 0.02 in per foot", it goes on to explain why that value was selected. – Jason K. Jul 22 '22 at 14:29
@JasonK. Because I picked an arbitrary setting when OP didn't specify if it was a distributed or point load. – Doresoom Jul 23 '22 at 15:53

score 6 · Answer 2 · edited Jul 18 '18 at 23:35

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Check out this site : http://www.msrlumber.org - it has all the answers to spans for most applications. There are several good sites that have tables, just google "lumber strengths".

edited Jul 18 '18 at 23:35

qxotk

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answered Apr 02 '12 at 23:58

shirlock homes

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The PDF proves to be a vital source of information. Very nice – Piotr Kula Apr 03 '12 at 10:49
Many years ago, we won't say when..... I had to study strength of materials charts in architecture class. With all the new LAMS, beams and trusses, the charts are more important than ever. – shirlock homes Apr 03 '12 at 20:15

Bryce · Answer 3 · 2022-07-24T08:24:21.183

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The American Wood Council offers just the tool you need at http://www.awc.org/calculators/span/calc/

Maximum Span Calculator for Wood Joists & Rafters/ You'll want 'live load', meaning people (and/or stray deer).

edited Jul 24 '22 at 08:24

answered Nov 19 '13 at 04:02

Bryce

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this link doesn't work for me, i see a pdf here https://awc.org/calculators/span/calc/ when i removed timbercalcstyle.asp – Jason K. Jul 22 '22 at 14:40

At a 6' span, how much can an SPF 2x4 turned on 3.5" end support?

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