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9-1/2" or 11-7/8" I Joists?

CTSNicholas's Avatar

Join Date: Mar 2014
Posts: 100

03-03-17, 10:45 AM   #1  
9-1/2" or 11-7/8" I Joists?

I will be purchasing 28' I-Joists for a build. If the support LVL is dead center, so 14' span....would 9-1/2" I-Joists be substantial, or will they feel a bit spongy? This is assuming just 3/4" T&G OSB is used for the subfloor prior to carpet. The specs say they clear spans up to 16'6" with 16"o.c. but I have always used 11-7/8" thick I-Joists for my projects so I don't know how the floor would feel with the lesser I-Joists.

Hoping to hear some advice from those who have or have worked with the two options to compare.


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Pilot Dane's Avatar
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Join Date: Mar 2003
Posts: 16,683

03-03-17, 01:23 PM   #2  
I do not like to go close to the limit and will usually go up a size so the floor feels more solid. It also has the benefit of offering more space in the joist bays for running ductwork and plumbing. Depending on what mechanicals you have that need to pass through your I joists you might need the extra height.

stickshift's Avatar
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03-03-17, 02:02 PM   #3  
Might be enough for carpet but insufficient if your taste ever turns to tile.

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