In my addition which is 26′ x 30′ Below is my two car gargage each 15′ wide by 26′ deep. Above will be a heated area with several rooms and some plumbing.
I was thinking of using I joists ( 9.5″)but after reading the thread here I decided to ask advice first. Boss Hog?
I will be running them over the 30′ lengths. there will be no stairs at all to below.
I will have a continuos support at the half mark of 15′ .
So without the supporting 2×4 walls x2 and 2×6 wall x1 . I will have a max span of 14 1/2 feet per side .
I will be installing hardwood above on top of 1/2″ ply on top of 3/4 OSB . One quarter of the area above will have 1/2″ Hardi board with tile on top.
Any suggestions?
Replies
14" floor trusses would be my guess. With some 2x6 strongbacks, you'll be good to go.
If you are doing this solo, then use 2x12's. They are much lighter. 30' floor trusses weigh a ton.
I don't like I-joists.
I will remember before I forget.
I asked a similar question last summer.
Built a 15'X20' 3 level addition. Garage below, kitchen & bath 1st, bedroom second. All the advice here said go I-joist over dimensional lumber, no discussion of trusses as 15' span would not demand it. Local yard engineering guy spec'd 11 7/8" I-joists @ 16", I laid 3/4" T&G 5ply over w/ glue and nailed w/ ringers evry 8". Floors are very solid. No bounce, no noticeable deflection. Will lay 3/4" hardwoods this spring/summer afetr breaking through.
I was very happy w/ advice I got from the brain trust here, happy w/ results and those I-joists sure are easy to handle. I am no bruiser and could handle 2 or 3 16 footers at a time no problem.
I wouldn't use 9.5" I-joists on a 15' span - They seem a little thin to me.
But 11/7/8" I-joists would work fine. So would 2X12s and 12" floor trusses. It mostly comes down to personal preference.
If you don't want to put in a dividing wall in the garage, an 18" deep floor truss would clear span it easily.
If you're using tile, I've read that the floor members should be 16" on center regardless of their design. I assume that's to keep the tile from cracking, but don't know for sure.
You mentioned 1/2" ply on top of 3/4" T&G - Why is that?
My hard wood floor would be running with the joists so nailing into studs would not be possible. My hardwood guys said he needs at least an 1" and a 1/4 then to nail to.
So the recommended 9 1/2 " is going to be bouncy? they do clear 17' at 16" on center in manufacture specs. My reason for asking was if they blow a little smoke when it comes to this.I don't want it to feel funny so 12" would be best?
Have you read the thread on floor vibration?Putting floor members closer together does little to decrease vibration. Making them deeper does a LOT to reduce vibration.Span charts don't impress me. The numbers they come up with are based on strength and deflection, not vibration.
The longest journeys start with the first step... and continue one step at a time.
Depending on the 9 1/2" joists and the manufacturer, 15' span is no problem.
For 40 PSF Live Load/ 10 PSF Dead Load= 9 1/2" TJI Pro 110 can span 15'-0" @ 16" o.c., and at 12" o.c you can span 16'-5".
With the same loading using 9 1/2" TJI Pro 230 you can span 16'-2" @ 16" o.c., and at 12" o.c. you can span 17'-8".
All of that is with L/480 Life Load Deflection.
Like I said - Span charts don't impress me. You can probably put them 4" O.C. and span close to 20'.I base my recommendations on my own experience and research. And I'm VERY conservative on floor design.But isn't floor design something you SHOULD be conservative? Nobody wants to spend a fortune building something and find out they have a bouncy floor.
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Boss, I haven't read the vibration thread in a while, but I did think of you the other day when I talking to a floor truss salesman. He was saying one of the advantages is that instead of solid blocking you run a 2x6 continously through the webs and that it helps with vibration. Then he went on to say that in Canada they design based on vibration etc. etc. and I was thinking, I already know that thanks to Ron. Bouncy floors suck.
Thanks for posting that - It's always nice to know that something I did was useful to someone.
Anyone who believes that the way to a man's heart is through the stomach flunked anatomy. [Robert Byrne]
Carpenters usually laugh at my "over design" because their "gut feelings" say they could've done it with 2xs. I haven't had a bouncey floor since I started specing TJIs. You have to spec more than just the joist depth and spacing. They may have up to 4 different types of joists for the same depth depending on the span you need.
Obviously every manufacturer has several different series of I-joists in each depth. But that doesn't mean that all of the different series are readily available wherever you're building at. Take this case for instance - You might be able to find some REALLY high end 9 1/2" deep I-joists that would be have acceptable performance. (Changing the moment of inertia does make SOME difference in the vibration frequency.)But those high end I-joists will likely be an expensive special order with a long lead time. (Stock I-joists are very competitive - Special orders aren't)Doing the floor with 11 7/8" I-joists would not only give better floor performance, it would likey be less expensive. And the I-joists would be easier to get.
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I agree with everything you've said. But for those situations that do come up where you need try to maintain to a specific depth, the opportunity is there.
It appears you have gotten poor information both from your supplier (3/4" and 1/2" sheathing) as well as from here.
The I-joist people will be nice enough to provide a design for you.
The big issue is the tile. You need to meet the deflection requirements of the thinset manufacturer. Make sure to tell the I-Joist people what type of tile and supplies you are using.
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My suggestion would be 1-1/2" x 12" I-joists @16". About 60#/sqft live load plus 30#/sqft dead load.
Edited 4/4/2007 3:23 pm by GHR
Wow, you actually posted information for a change, instead of just posting negative criticisms.
Unfortunately you're wrong.
"Wow, you actually posted information for a change, instead of just posting negative criticisms."
I thought that too, but didn't say it.
Maybe he's finally learning something from hanging around here. At least his advice is improving. (a little)
If I had eight hours to chop down a tree, I'd spend six sharpening my axe. [Abraham Lincoln]
Looks like the 12" will do the trick then and bump up from the 10" to be safe.
Am I ok with the 3/4 osb with 1/2" ply over it? both glued and screwed?
I would think so myself. Thats 1 1/4" for nailing the hardwood to.
Or do they make advantec thats 1 1/4" already? Remember I wont have the joists to nail the hardwood to since they will run the same direction as the hard wood. My only problem then would be the tile section would have to be applied on the advantec directly instead of swapping out the 1/2" ply for 1/2 " hardi in the bathroom.
I don't know why the 1/2" and 3/4" subfloor wouldn't work fine. but I know very little about hardwood floors, and virtually nothing about tile.I don't know if anyone sells full 1" thick T&G anymore. We used to have 7/8" ply available around here, but not 1" or thicker. You'd probably have to ask about that locally.Or maybe someone else will have some more useful thoughts...
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We install hardwood and tile on 3/4" Advantech and 1/4" or 1/2" backerboard on virtually every job. With joist deflection of L/360 or L/480 you'll be fine. Check out the John Bridge tile forum if you want some tile-specific advice.
Woodguy - are you saying 3/4 advantech is not enough for hardwood?
Not arguing, but we've always done just that - generally keeping the hardwood perpendicular to the joists, pl premium under the tongue, no paper. I'll change if someone gives me a good reason.
BTW - I have 9-1/2" I joists spanning 15' in my house - floors are solid. I installed the 42' lengths by myself - love those I joists! The truss mfr talked me out of floor trusses, based on cost.
Treat every person you meet like you will know them the rest of your life - you just might!
Sorry, my other post wasn't clear. What I meant to say was that we install 3/4" hardwood on top of 3/4" Advantech all the time. Tile gets installed on backerboard on the 3/4" Advantech as well.
even when you cant hit the joists with your nails? So you just nail the hardwood into the sheathing?
Yes
All the hardwood installers I have used insisted on installing perpendicular to the joists. What are your thoughts on that?
I think the reason for proposed the extra floor thickness is because the OP wants the hardwood parallel to the joists.
Thats true. This is the only reason for me going extra thick so the floor guy has something to bite into with his nails.
Everything else being equal, it's nice to be able to go across the joists, but as long as the subfloor is at least 3/4" Advantech we never worry about it. We use/have used several different floor guys and they will say the same thing.
There's nothing wrong with thicker subfloors or going across joists, I've considered using the business name "Overkill Construction," but I don't think it's necessary.
Now 5/8" subflooring, or even 3/4" if it's not Advantech, I might have a different opinion on.
At least my comments are supported by a majority of professionals.
"At least my comments are supported by a majority of professionals."
B.S.
The vast majority of you posts who a complete lack of a working knowledge of construction.
Your posts also show a complete lack of courtesy and tack. They're mostly self-congratulatory back patting about how smart you think you are.
Do you REALLY think they're laughing with you?
What professionals?