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Discussion Starter #1 (Edited)
I am tryin to build my wife and i a small apartment and have built a cinderblock stem wall foundation with dementions 26x28ft.

I have finished the blocking and layed the 6mil sheeting on ground , my sill sealer foam and pt sill plates along the perimeter. I have spot piers evenly spaced in the inside (every 7 ft length wise by every 6 ft width wise.) I am currently about to install my beams (4x10). My question is if it is ok to use 2x6's as my joists for the floor. The span to the beams will be at 7ft and I will be going 16" on center spacing.

I am a first timer at this and would like all the help I can get. Any help or advise is greatly appreciated. Thank you
 

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Civil Engineer
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The size of joists, beams and most other standard framing elements are usually dictated by code. If you have a custom designed house, the architect will typically specify the required size of the framing elements, usually assisted by a structural engineer. In some communities, you do not need a permit to build, and therefore you can size your framing elements based on any code you prefer, fundamental analysis by an engineer or architect, or simply by guesswork or copying the size used in other houses.

You did not indicate where you were building, if you are planning to follow code, or you have some other basis of design. Do you have plans for the apartment? If you describe your design basis, it would be possible to discuss if the selected joist size is OK. You also need to know the species of wood you plan to use, as that affects the allowable span.
 

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Floor joist span table I can find on line do not even include 2x6. They start at 2x8 with 12' spans maximum.
 

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AHH, SPANS!!!
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I think a 5' span is pushing it for 2x6 joists so 7' would not work imo. I feel comfortable at about a 4' span between bearing points with 2x6 joists. this is with spf standard framing lumber...
 

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If you do not mind a bouncy, squecky floor then 2 X 6's will "work".
I'd go with 2 X 8's/
Also please tell me your not going to use a solid beam that size.
Always better to gang up 2X's then to use a solid beam.
 

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8' is the length I am comfortable at. very rarely used 2x6. Only in a small porch, and never going to be tiled just lino. (carpet would be ok too)
 

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This link will provide you with span tables from the 2009 International Residential Code. As Daniel said it is unclear what code if any you are or are not required to build by. These tables will provide you with the maximum spans for various size joists, wood species and lumber grades.

Hope this helps

http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_5_par020.htm

this is span tables from the American Wood Council. these tables are the basis for those contained in the IRC.

http://awc.org/pdf/STJR_2012.pdf

Good luck!
 

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Our old cottage has 2 x 6 floor joist on just slightly over 7 foot spans. The floor is a bit bouncy (compared - say - to the 2 x 10's on 10 foot spans in our house), but is has been OK and has been there since 1974. The thing we notice most in the cottage is less the bounce and more the way things shake if someone stomps or runs across the living room.
 

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Discussion Starter #12 (Edited)
Thanks everyone! I will be going to get some 2x8's today.
Also, I did not run solid beams but built them out of 2x10s . I am building this in the east Texas piney woods area. In the country so no codes or limitations.
Another question though.... If I go with the 2x8's will I be able to put ceramic tile down or do I need to go bigger to allow for these.

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Discussion Starter #13
Matthewandbrand said:
Thanks everyone! I will be going to get some 2x8's today.
Also, I did not run a solid beam but built them out of 2x10s . I am building this in the easy Texas piney woods area. In the country so no codes or limitations.
Another question though.... If I go with the 2x8's will I be able to put ceramic tile down or do I need to go bigger to allow for these.

Sent from my iPhone using DIY Forum
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Matthewandbrand;1043306. If I go with the 2x8's will I be able to put ceramic tile down or do I need to go bigger to allow for these. Sent from my iPhone using DIY Forum[/quote said:
To improve stiffness, try spacing the joists a little closer (say 14"). That way, each joist will be carrying less weight and will therefore deflect (and bounce) a little less.
Also, solid bridging between the joists at mid span helps to stiffen the whole floor by spreading the weight over several joists.
 

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what will be the span of your joists? what is the species and grade of your lumber?
 

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JOATMON
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Given the cost difference between 2x8 vs 2x10....in the long run, I think you would happier with 2x10.

Something else to consider...the typical sub-floor is 3/4" T&G. My architect had me do 1 1/8" T&G for my 2-story addition (pics in the link in my signature). OMG (I hate that phrase but it applies here). Walking on the 2nd floor of my addition is about par to walking on a concrete slab. The sheets were maybe $15 more/sheet....but some of the best money I have spent.

So...upping the sub-floor can go a long ways to making it stiffer....especially important if you want to put down tile.
 

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Discussion Starter #17
GBrackins said:
what will be the span of your joists? what is the species and grade of your lumber?
The total span is 16'.. But I was told to go by design span? Which was explained to me to be from the face of the supports . In which case the design span for each joist would be 6 1/2 '.. They are going to be spaced 16" on center . They are grade 2 SPF

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With the 6 1/2' span, 2x8s would allow for ceramic or natural stone, according to the john bridge deflectolator.

But hell, if it were me, I would just use 2x10s. :D
 

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i frame both additions for renos and custom new homes... the only time we use 2x8's is when we have to match the ceiling heights of the existing in the house.. and even then we try to get 7 1/4 " tji's or ojts as they can span longer distances and stay straighter tji's especially

as for 2x6... the only thing i would use those for in regards to a floor would be a landing for stairs and thats it.. by code a 2x6 is only good for walls its not even considered a floor joist by the canadian code
 

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The total span is 16'.. But I was told to go by design span? Which was explained to me to be from the face of the supports . In which case the design span for each joist would be 6 1/2 '.. They are going to be spaced 16" on center . They are grade 2 SPF

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SPF #2 at 16" o.c.
live load = 40 psf dead load = 10 psf
deflection = L/360
from Span tables of 2009 IRC

2x6 maximum span 9'-4"

2x8 maximum span 12'-3"

2x10 maximum span 15'-5"

2x12 maximum span 17'-10"

for 16' span I'd probably go with 2x10 at 12" o.c. which has a span of 17'-3", either that or reduce the span.

with a deflection of L/360 you could expect the following deflection = (16'x12" per ft)/360 = 0.53"

when you near the maximum span of joists they tend to get more bouncy.
 
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