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Old 09-22-2009, 01:20 PM   #1
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Divided room on second floor

I can't seem to find an answer on this.

The second story of our house has a large open room, I would like to divide that space into two rooms.

The wall I want to add would span 14 foot and would run in the same direction as the floor joist (which also span 14 foot).

There is not a wall under this 14 span on the first floor.

Can I add a second floor wall without having a load wall on the first floor?

Is it just a matter of sistering joists?


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Old 09-23-2009, 06:04 AM   #2
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Adding a partition wall does not require additional structural changes. You can even use 2x3 lumber to save a 1" of space.


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Old 09-23-2009, 06:54 AM   #3
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Yup, as Bill said - build away

You do not need a wall underneath as the new wall is not load bearing
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Old 09-23-2009, 08:59 AM   #4
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Thank you.
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Old 09-27-2009, 02:38 PM   #5
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When you are seperating a room into two rooms all you need to do is put up a stud frame work then use some 8x3 feather edged plaster board and scrim and compound the joints so it will save you plastering.This method is called dry lining which is used a great deal now in the building trade,hope this helps.
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Old 09-27-2009, 04:09 PM   #6
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I think this question requires a little more thought. If the OPS has a 2x12 joist spanning 14 feet, and it is standard grade lumber with an allowable bending stress of 1500 psi (pretty typical), the maximum load per foot that joist is capable of carrying at a factor of safety of 1.0 is approximately 180 lbs/ft. Depending on the state, code requires you to support about 40 pounds per square foot live load (in MA where I live, the load is either 30 or 40 psf depending on the type of room).

If the joists are 16 inch OC, each joist is presumed to carry about 50 pounds per foot live load, plus of course the dead load of the floor. The additional dead load from a partition wall 8 feet tall, with a 2x4 bottom plate and a 2x4 top plate, with 2x4 studs 16 inches OC, with 5/8 inch drywall on either side, is by my computations about 50 pounds per foot. This ignores any additional load picked up by the wall from the ceiling above. I realize this is a non-load bearing wall, however if it is pushed up against the ceiling above, it may carry some extra load.

If the non-load bearing wall is aligned with a joist, it is likely to overstress the joist. This may not cause failure, but may cause more deflection than you like. I believe the OPS had a valid point in considering sistering the joist below to minimize this potential, at the very least it is worth taking a closer look at.


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