# 4 x 4 floor joist possible?



## ditastanton (Jan 7, 2017)

Beginning to think about building for fun a small barn for normal storage of mowers, tools, etc. Would like a second floor hence need floor joists- first floor is concrete. In order to keep the second floor a bit lower- and because I have a mill and like 4 x 4s- I would like to use 4 x 4s on 16 inch center spanning 8 feet. Safe? Ok? No codes here in North Georgia pertaining to this and not seeing any southern pine wood tables that speak of anything joist-wise that isn't 2 x this or that. Is a 4 x 4 about like a 2 x 8? thanks....


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## stick\shift (Mar 23, 2015)

You can't even use a 4x4 as a post for a deck any more, no way this would work or be allowed.


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## MTN REMODEL LLC (Sep 11, 2010)

stick\shift said:


> You can't even use a 4x4 as a post for a deck any more, no way this would work or be allowed.


Stick.... I have not had a chance lately to build a deck lately (I'm mostly retired), but could you explain your reference above. Is prescriptive allowances been changed. IRC...???????


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## jlhaslip (Dec 31, 2009)

The depth of a joist is what gives the floor its strength in terms of deflection.
Width of the joist times (depth squared) is a rough formula.

4 x 4 calculation
4 times (4 squared) = 4 x 16 = 64

2 x 8 calculation
2 times (8 squared) = 2 x 64 = 128

A 2 x 8 joist is twice the strength of a 4 x 4 in deflection.

Our friend Daniel might be along shortly to give a more valuable opinion.


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## Gary in WA (Mar 11, 2009)

_____________Welcome to the forums!____________________________

Using SP #2 --- 1400fb; 2x4= 357# 
Dbl 2x4= 595#
4x4= 833#
2x6= 945#
2x8= 1642#
4x6= 2058# that is total load (per square foot) with an 8' span. Divide total load by 1.33 to get your 16"oc---- or per foot of joist across the 8'. eg,; 833/1.33= 626# per running foot of load.

Gary


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## SeniorSitizen (Sep 10, 2012)

Being you have a mill just make the second floor solid 4x4's.


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## woodworkbykirk (Sep 25, 2011)

if theres not much weight on the floor and its not inteded for any sort of living space you could maybe get away with 4x4s' but i wouldnt install them 16" o.c i would do 12" and block them. 

regarding the deck comment.. 4x4's havent been allowed within code for a bearing post for over 10 years in most regions.. they deflect under heavy winds and heavy loads.. they are only accepted for hand rails. 6x6's are the standard now for bearing posts


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## ditastanton (Jan 7, 2017)

SeniorSitizen said:


> Being you have a mill just make the second floor solid 4x4's.


For real? Interesting idea! I have tons of southern pine........


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## SeniorSitizen (Sep 10, 2012)

Yes, for real and you could stack 4x4's and build solid walls log cabin style. I know of an old stucco house probably built in the 1930's of stacked 2x4's. No insulation in those days but really didn't need it. Hang wall decorations/pictures where ever.:biggrin2:

Then there is the story of my late father and an old man building a log house with nothing but an axe and it was so tight a door had to be cracked open to get the kerosene lamp to burn.:surprise:


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## Gary in WA (Mar 11, 2009)

Oops!

Late last night, brain fart. 
" Divide total load by 1.33 to get your 16"oc---- or per foot of joist across the 8'. eg,; 833/1.33= 626# per running foot of load."------------------ should be 626# *total load, *not running foot= 78.25# (need to divide by span; 8'). Sorry about that.

The Deck Code with many US states using for their prescriptive guide allows 4x4 posts; example in beginning (pp. 4, 5) and also in commentary (C6) at very end; http://www.awc.org/pdf/codes-standards/publications/dca/AWC-DCA62009-DeckGuide-1007.pdf

Gary


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## stick\shift (Mar 23, 2015)

MTN: Figures 8, 9, 10 in the DCA 6. Based on 2009 IRC.

http://www.awc.org/codes-standards/publications/dca6

Local codes vary, but at any rate, this is the way thing are heading and it's good method regardless of whether or not it's required by law.


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## ditastanton (Jan 7, 2017)

Thanks all.....most helpful info and I really like the easy formulation methods of checking strengths of joists. I think I'll move to conventional 2 x 8s. Can use my 4 x 4s from smaller logs for various sills and plates. Can't wait for our 10 degree weather in north Georgia to warm a bit.


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## puppit (Aug 31, 2021)

stick\shift said:


> You can't even use a 4x4 as a post for a deck any more, no way this would work or be allowed.





stick\shift said:


> You can't even use a 4x4 as a post for a deck any more, no way this would work or be allowed.


No span allowance, or load considered? That's interesting, given pier and deck blocks are specifically designed for 4x4 vertical struts. What ordinance are you referring to?. State, county, and local.. what calculation are you applying? And where do we verify your info? Curious.. being it's the standard..in most places. Are you east coast southern possibly? Flood zone?


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## Nealtw (Jun 22, 2017)

puppit said:


> No span allowance, or load considered? That's interesting, given pier and deck blocks are specifically designed for 4x4 vertical struts. What ordinance are you referring to?. State, county, and local.. what calculation are you applying? And where do we verify your info? Curious.. being it's the standard..in most places. Are you east coast southern possibly? Flood zone?


We tend to ignore old posts like this.  Jan 6, 2017


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