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cdrew23
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# Posted: 22 Oct 2014 11:02
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How i constructed a floor joist system left the subfloor panels extending to the center of the rim joists, instead of to the outside edge. Should my framing then be slightly smaller than the perimeter of the rim joists so it sits completely on the subfloor, or should i cut small scraps of subfloor and screw into rim joists so framing can extend completely to original intended dimensions? See photo for reference (this isnt my photo or project, but shows where my subfloor ended up on rim joists - in the center, not the outside edge).
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bldginsp
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# Posted: 22 Oct 2014 11:55
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Yes I'd put in the strips, but if the rim joist sits on a spread footing and a sill plate I'd also double block behind the rim. But if the rim is spanning across piers that won't really work, unless you run a second joist between piers or solidly bolt/screw it to the original
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cbright
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# Posted: 22 Oct 2014 13:55
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Why were you putting the ply wood on with the same orientation as the joists? Spanning across 7 joists (for 8' sheet on 16oc) is how I have always done it.
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cdrew23
Member
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# Posted: 22 Oct 2014 14:29
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@bldginsp - the floor joist stystem is set on 2 beams spaced 10' apart, with 1' of cantilever on each side or a bit less
@cbright - I oriented the boards as you said, with the span across 7 joists.
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MtnDon
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# Posted: 22 Oct 2014 14:32
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A big issue is the subfloor sheet edge has virtually no support along that side. The wall bottom plate can still be nailed to the rim joist but that rim joist will not be properly tied to the floor joists. You may have nails through the rim into the ends of the joists. That is not a joint that will be able to resist any outward pull force. The sub floor sheathing should always completely lap over the rim joist and two more joists inward.
The way to do that would have been to offset the initial sheet to one side and trim off. Then on the other side more sheathing would be trimmed off. How much offset to start with depends on the width of the building. OR the floor structure could have been built a couple inches narrower.
Ideally the rim should have been doubled up. That makes it stronger under the wall and makes adding any future porch or deck floors better.
If the sheets are laid the same way as in that photo, that is incorrect. That does not make the floor diaphragm as strong as it should be. The long dimension of the sheet should always be perpendicular to the joists.
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cdrew23
Member
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# Posted: 22 Oct 2014 15:17
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@MtnDon - This is how I will plan to do every project from here forward! Any suggestions on the best way to deal with the situation since its glued and screwed already? Thanks
Also, my sheets are not laid the way in the photo, it was just to illustrate where the subfloor made it to on the rim joist.
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Don_P
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# Posted: 22 Oct 2014 22:43 - Edited by: Don_P
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Without the edge tied to the rim well the floor diaphragm is compromised, there is no real boundry connection. The rim is held in place mainly by the joist end nails in withdrawal, if there is a deck ledger attached to that side, that is not a real solid assembly. More than a few houses are framed with the narrow strip under the sole plate of the wall, I did it for years. From the American Plywood Association, the "strip" should be 16" or wider. Basically this means you either need to shrink the building ~1/2" per 4' to allow for the toungue and groove or you need to buy an extra row of floor sheathing and use less than half of it. Normally I can use it on the job, stair treads, gussets, lining closet sides behind the drywall to give screw backup anywhere on the sides, there's usually places to use it but it is ~$30/sheet.
For what you have now, a row of blocking nailed to the rim with the floor sheathing well nailed to it would certainly help a lot. then the strip and build walls flush to the outside of the rim.
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