Your experience 19' floor span w/I-joists and 2x12 SYP

[MidwestEric]

Hi everyone,

As we are getting ready to build the 20x30 1 story, and reviewing plans and materials, I've come across trying to decide on I joists or 2x12 joists. From what I have read, either option can result in a floor that at least some people find to springy..  The spec'ed I joists 16" OC result in a little better than L/480 deflection and 2x12 @ 12 OC are a little worse. By worse, I have read about frequency and using closer spacing results in less deflection, but nothing to cancel out low frequency transmission of a 20' 2x12.  I guess the primary issue is 20'/480=.5 inch

So I called the Trus Joist local dealer and found the next step up from TJI-360s are TJI-560s.  Both are 11 7/8. The price was crazy, jumping from $2.80 LF to $4.10 LF.  So no way is that going to fly.

So for those that have with either I joist or 2x12 with no mid span support, what do you think?  Too springy/ not to springy? Seems like the less expensive solution is 2x12 SYP and a mid span support.  I just have to wonder what has proven to work out just fine.

Thanks

[UK4X4]

I've been juglling similar issues with a 26ft wide...

Thicker I joists / center beam - added foundation / support beam

there are so many ways to accomplish the same thing

cost implications seem to be pretty similar at the end of the day.

Looking at this long term for the price of two decent tires you get a better floor !

the other route is going to a 14" 360 and use rim board this gives you L826 or 1/4" at full live load.

another is fit an lvl at 15ft run joists the other way giving you only a 15ft span

many ways to skin this cat !

[MidwestEric]

I am wondering maybe if it works out OK with the L/480 I joists @ 16" OC 19' span. Hope someone chimes in that.  What did you find price wise on the 14" I joists?

[Alan Gage]

My dad has i-joists in his kitchen addition that are right at L/360. You don't notice any bounce if a person walks through the kitchen but do if a small dog goes trotting across. Kind of drives him nuts but I never notice it when I'm there unless he mentions it...or I feel like giving him a hard time.

Alan

[Rensmif]

Hi everyone,

As we are getting ready to build the 20x30 1 story, and reviewing plans and materials, I've come across trying to decide on I joists or 2x12 joists. From what I have read, either option can result in a floor that at least some people find to springy.. 

Seems like the less expensive solution is 2x12 SYP and a mid span support.  I just have to wonder what has proven to work out just fine.

Thanks

I am still in the decision stages on a 20x30 myself, one thing for sure is I plan on using a mid span support for the very reason of it would drive me mad every time I walked across it.  I would actually be looking for the bounce, and at 270 lbs it would not be hard to find. 

My reading also discusses a floor too springy so a center beam seems like the best and most economical way to go.

[walkabout]

I spent $1,685.75 on 16" engineered floor trusses that were 19-2 OC for my 20x27 cabin.
I had some special trusses in this order tool as I needed different ones for the stair opening and so that I could integrate the header over the windows in the basement into the floor.
I went with engineered trusses so that I could run all my duct work/plumbing/etc between and through the webs to save headroom in my already restricted 6'6" crawlspace. I do not have any center beams.
I can't remember the rating on these trusses, but I believe it was considerably higher that i-joists.

I think I had 18 trusses in total at 20' length. So the cost was approx $4.70 per foot which is quite a big higher than you are looking at. For me it was/will be worth it as I don't have to worry about support in the basement and I save on my precious headroom.