floor joist question


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Old 06-13-15, 05:51 PM
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floor joist question

I had a question on wall stud and main support in crawlspace.Is a room divider stud that has the seperation wall on top of it ever built between two of the floor joists or are they always directly on top of the floor joists that support the room.?
It goes in the same direction as the joist that are on top of main beam.
Any info is appreciated.
 
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Old 06-13-15, 06:43 PM
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OK, I've read it 6 times and can't make sense of it. What type crawlspace is it? How high is it? Is it a basement or attic? Studs are vertical. Joists are parallel. Top plates are set under the floor joists above them and are attached to purlins or nailers where the wall will be between the joists. The purlins are attached to the floor joists so they are flush to the bottom of the joists.
 
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Old 06-13-15, 08:10 PM
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LOL Chandler! I read it many times too. I have no idea what the question is either.
 
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Old 06-13-15, 09:01 PM
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i dont know the correct building terms for it but the wall that seperates 2 side rooms is what im speaking on- living room and bedroom-...and at the bottom of it under crawlspace is what im asking on ..if you were to go under the home in crawlspace the wall stud nails you see thru the plywood are between the joists..and all nails in the same direction of joists to the end..I measured top area and then in crawlspace.
deflection is happening...in drawing of the set up looking from under it in crawl space the red line is the wall and the black are the floor joists coming off the main beam..10sfile:///C:/Documents%20and%20Settings/Phillip/My%20Documents/Downloads/KIMG0278.jpg

having trouble with pics..
3/4 in plywood an 2 by 8 wood for floor joists that are about 16 inches apart
 

Last edited by trotter; 06-13-15 at 09:27 PM.
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Old 06-13-15, 09:06 PM
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Yes, it's common for interior walls to fall between joists and they sit only on the subfloor, because they are not load bearing. It's nice if the framers put perpendicular blocking between the joists, but that rarely happens. You didn't say what your subfloor is, so maybe post back and tell us how thick the subfloor is, whether it's plywood or 1x6 diagonal or what. If it's sagging, you can probably jack the wall up from below with a hydraulic pump jack and install the perpendicular blocking yourself, as needed.
 
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Old 06-13-15, 09:28 PM
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3/4 in plywood an 2 by 8 wood for floor joists that are about 16 inches apart..and there is no blocking anywhere there..the ceiling is showing seperation from that wall, depending on time of year
 

Last edited by trotter; 06-13-15 at 09:47 PM.
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Old 06-14-15, 04:29 AM
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2x8 joists....How long are the joists between the support piers and/or foundation. Your deflection is more a factor of whether the space is over spanned and carrying the extra weight of the wall (load bearing or not). Also, is the deflection across the whole floor or only between the one joist bay where the wall sits?
 
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Old 06-14-15, 04:39 AM
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The 2x8 floor joists are probably overspanned (too weak to do the job) if they are 16" on center and are longer than 11 ft, unsupported. Also, lumber in a humid crawlspace will bend more easily, so it could be a combination of factors that are leading to the problem. 3/4 plywood is a fine subfloor, so no weakness there, other than the missing blocking. If the subfloor visibly sags, then fix it as mentioned earlier. If the floor joists are overspanned and bowed, you may need some footings and a beam to cut their span in half and raise and support them.
 
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Old 06-16-15, 11:18 AM
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Thanks for all the helpful info.So Would i need any form of a jack to remain there permanently or will the bracing after i jack it up and install it work?
The joists are not showing any bowing but as u stated may be over spanned.--

Ill point out this is a duplex and no issues on the other side from this are occurring anywhere .
.there had been a point where water had accumulated in the past under here about 15 ft away -low spot in corner now w sump pump - with very high waters so this may have factored it-not sure.
 
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Old 06-16-15, 03:04 PM
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Jacks are always a temporary solution and cannot be permanent.
 
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Old 06-17-15, 04:53 PM
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Ive seen those "smart jack systems" advertised but not sure I would want to go that route..I do want something permanent without a lot of room for more deflection..
Thanks
 
 

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