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toyota_mdt_tech
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# Posted: 19 Jul 2011 10:43am
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Ok, something else I have been wondering about. My next project shows 24 foot floor joist spans using 2X10 at 16" OC. But at the halfway point, there is a load bearing beam in the crawlspace. The joist overlap a foot either side and are anchored together, the splice being right over the load bearing beam. So far, no isses with that. My question is, floor sheating. Will use 3/4" T&G glued and nailed, but with the joist being staggered at the splice, how does one secure the but joints when they wont align over the splice as the joist will stagger or shift 1 1/2" from one side to the otehr becasue of the splice. I know flooring will lay opposite direction as joist spans, but this will put butt joints floating over the edges of the joist. Even if i lay them same direction as the joist. Or do I start from the center over the beam, sheet it to the outside wall, then from the opposite side, stagger the sheating, groove side over the beam in the middle, work outward to the other wall, ? (or I suppose i could start from the wall, work inward, 3 sheets would put me at the center, then "shift" the sheating 1.5 inches and finish going across to the opposite wall? Just trying to get everything in my head before I start my next project. I have a few yrs before starting, but want to work through the small details ahead of time.
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Borrego
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# Posted: 19 Jul 2011 05:04pm
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Options to make the joists line up across the house:
1) hang them from the beam and rim joists instead of setting them on top. Not quite as strong and harder to do but solves your problem easily...
2) Instead of staggering the joists, butt them and fasten with a metal connector (like a skinny bucket) or straps or double sister where they meet. Use a thicker center beam if necessary like a 6x10 or sister your 4x10's with 2x10's on each side.
3) Do it like you're saying but sister every joist on one side with a 2x4.
I wouldn't recommend doing as you say in your post, you'll regret it......
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toyota_mdt_tech
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# Posted: 19 Jul 2011 10:14pm
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Quoting: Borrego I wouldn't recommend doing as you say in your post, you'll regret it......
I'd agree. I thought about it and I'd have to cut a chunk of filler 1.5" to fill in where I shifted the sheating over and that strip would end up under and outside stud wall which would make it weaker IMHO. I like the "sister" affect or the butting them on top of the beam, using a larger (wider) beam and maybe some hurricane ties and toe nailing to keep them parallel and not shifting. Plans show bracing between the joist also. I can probably delete those in the plan before i submit it. The plans I buy tend to be over engineered so they are suitable for all areas.
Thanks and glad you understood what I was after. I think that about covers it for now until I can think of something else. ;D
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caveman
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# Posted: 20 Jul 2011 09:31am
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you will want to stagger the joints in the sheathing so it means you will need to cut the sheets to fit the layout. this is old school stuff before joist hangers were popular. if you start with an 8 ft sheet along the back wall for instance, and run the length of the building, on the next course you will cut the first piece to break on a different joist and use the cut piece somewhere else.you will, however have a seam down the center of the drop sill and to support that you can install bridging between the joists there. kinda hard to explain but simple when you get started
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toyota_mdt_tech
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# Posted: 20 Jul 2011 05:31pm
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Caveman, that is what I would of done if I ran into that. I just want to make sure its up to code. Dont want an inspector coming out and saying "this isnt right". I worried alot on my existing cabin, but it passed with flying colors. I would overlap the floor joist for the splice 2 feet on either side of the support beam and I"d have to get 14 footers for a total of 4 foot of overlap which I know makes for a real strong joint. But witht he support beam, there is only down force, no pulling or sideways pushing. We dont get tornadoes or hurricanes. :D
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MtnDon
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# Posted: 21 Jul 2011 03:34pm
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Regarding the blocking. Blocking is usually only called for when joists are taller than a 2x12. However it is always a pretty good idea as it helps keep the joists where they should be. Solid blocking is supposed to be used between joists over any support beams like the central beam though when the joists overlap. When using a cantilevered joist on the side(s) there does not need to be any blocking over the side beam unless the cantilever is greater than 24 inches. (I think it is 24" ?)
Blocking over a beam like that should be solid, not the X type.
Re the sheathing. Keep in mind T&G sheathing loses about a half inch in width. Try not to have a narrow strip along the side walls. Reason; IF a ledger is later added for a deck or a porch it is best to have a wide sheet (2 feet or more) nailed down to the joists and the rim to provide greter horizontal force strength where the ledger might be attached.
Simply stagger the sheets at the center. Use scrap 2x material to scab in as required.
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soundandfurycabin
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# Posted: 22 Jul 2011 07:09pm
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I too would do as Caveman suggests. On the one side of your cabin, you start off with either a full sheet or some multiple of 16", such as 48". On the other half, you start each row with a cut sheet that is a multiple of 16" + 1.5", ex. 49.5". If the length of your cabin was 32', then you could just use the other part of each cut sheet at the other end of each row, where the last piece will be a multiple of 16" - 1.5", ex. 46.5". Since your cabin is 30' long, it will be a bit more complicated.
Try drawing the layout on paper and you'll quickly see how best to cut the sheets and where you can use the cut offs. If you haven't already installed the floor joists, then consider offsetting one side by 3/4" and the other side by 3/4" in the opposite direction. That will make it easier to reuse cut offs from one side of the cabin on the other side.
As an example, the first row on one side could consist of sheets cut to 31.25", 96", 96", 96", 40.75", and the first row on the other side would be 16.75", 96", 96", 96", 55.25". The 40.75" and 55.25" pieces can be cut from one full sheet; and, the 31.25" and 16.75" pieces can be cut from a half sheet. You should be able to cover your floor with 22.5 sheets.
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Borrego
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# Posted: 22 Jul 2011 09:49pm
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Remember you can't (code) or shouldn't (structure) go less than 24" on your plywood rips....
MtnDon referred to this for good reason... This will make you use extra sheets. But it's required, unless you're not being inspected, of course, but still a good idea.
And your first row will start with an 8' sheet, so your second row will start with a half sheet, then a full sheet to stagger the sheets. Take this into account when doing your layout ;-)
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soundandfurycabin
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# Posted: 23 Jul 2011 04:51am - Edited by: soundandfurycabin
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Borrego, the 16" lengths are short but not a big deal because the joints have to be staggered, so every second one will be longer. It meets code where I am but I'm not familiar with US codes. If he has minimum lengths then adjust accordingly, for example:
31.25", 96", 96", 96", 40.75" on one side
64.75", 96", 48", 96", 55.25" on the other side
31.25" + 64.75" = 96"
40.75" + 55.25" = 96"
In any case, my advice is to lay it out on paper so as to avoid too much waste, especially if using Advantech or a similar expensive product.
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Erins#1Mom
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# Posted: 23 Jul 2011 09:02am
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No insults to the other females on this forum, but I have difficulty wrapping my mind around each of your suggestions. I need visual/hands on. MD yours I understood perfectly and the other recommendations to lay it out on paper (visual).
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Borrego
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# Posted: 23 Jul 2011 01:05pm
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Sound and fury - Your ideas are fine, although the overlaps on some of the sheets would be too short for down here. End of sheet to center of next sheet. Period. So your calculations wouldn't work for me, that's why my original suggestions were what they were. Just how we build down here....
Erins#1mom Most of us have had years of hands on with this stuff, I don't think even drawings would help the uninitiated, you just have to do it. And this is a simple project :-)
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PlicketyCat
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# Posted: 23 Jul 2011 08:04pm - Edited by: PlicketyCat
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When I lay split joists over a central girder, I usually go ahead and abut the joists over the girder and the scab the joint with a 2' length of ply or scrap dimensional lumber on either side. No funky staggering or sheet alignment issues, no ledger notching, no need for hangers since you've essentially just created a straight long joist.
Edited to add a pic for the visual folks :)
(see, not all women go for the complicated solution all the time LOL)
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Borrego
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# Posted: 23 Jul 2011 09:32pm
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Like I said.
The simplest and best way to go, still think :-)
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PlicketyCat
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# Posted: 23 Jul 2011 09:52pm
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And if you center your subfloor sheet over the join instead of along it, you don't even really need a tie/scab (unless req by code) since the sheet does the job for you. Even less work & materials as long as your dimensions are evenly divisible.
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toyota_mdt_tech
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# Posted: 23 Jul 2011 10:01pm - Edited by: toyota_mdt_tech
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Nice plickety. It was one of the options I was thinking of. I seen/read joust need to hang on by 1.5" on each end, so that would explain the triple'd beam. I'd do my blocking there over the girder to keep them from flopping on their sides.
I know of many ways, I just wanted to see what is acceptable to an inspector. Looks like i have many options. I suspect this may be the cheapest.
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Borrego
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# Posted: 23 Jul 2011 10:03pm
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Right on.....! Save time, save money, better product, that's what I'm sayin'
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PlicketyCat
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# Posted: 23 Jul 2011 10:17pm
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TMT - I've never had a girder that was narrower than a 4xS, just like the sill beams. Although I suppose if it were deep enough (over 12") a 2xS would hold the weight, but I wouldn't trust it ;) -- but a 4x6 is going to be less expensive than a 2x12 or some other really wide dimensional lumber, so why bother?
Borrego - you know it!! Built-up beams, scabs, ties and scarfs... all wonderful things ;)
Tip: most wall studs are 91 1/2 inches in an 8' wall (subtracting 4 1/2" for the bottom & top plates). If you buy 10' wall studs instead of 8' -- each stud leaves you with exactly enough scrap for two stiffener blocks between 16" oc joists. Since wall and floor framing is usually the same spacing, this works out wonderfully without waste or having to spend extra on lumber just for blocking.
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Borrego
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# Posted: 23 Jul 2011 10:22pm
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Quoting: PlicketyCat Tip: most wall studs are 91 1/2 inches in an 8' wall (subtracting 4 1/2" for the bottom & top plates). If you buy 10' wall studs instead of 8' -- each stud leaves you with exactly enough scrap for two stiffener blocks between 16" oc joists. Since wall and floor framing is usually the same spacing, this works out wonderfully without waste or having to spend extra on lumber just for blocking.
You've done this before, eh? :-)
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PlicketyCat
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# Posted: 23 Jul 2011 10:29pm - Edited by: PlicketyCat
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You betcha :D When you're working on a tight budget, with the nearest road a mile through the forest and the nearest store 3 hours away, and running all your tools on battery or generator you learn really quick how to minimize material waste, number of cuts, and supply trips ROFL
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