I'm building a lumber-framed office inside a commercial warehouse. It's essentially an 8' x 30' x 9' box with a ceiling and "second floor" made of 2x6" joists, with 2x6" rim joists resting on top of the two 2x4" walls. Note that the second floor will only be used for light storage.

Because one wall of the office is up against the wall of the warehouse, I can't end-nail the joists. I could toe-nail the joists, but I want to use metal hangers instead. Is there any problem with doing do, even though the rim joist and the hangers will be resting on the top plate?

Office inside commercial warehouse

Building Construction

The back wall of the building is a decorative cinder block. I’ll anchor the top of my walls to the back wall.

Rear Wall Construction

The front wall is large steel studs. I bolted the top of the outer wall to one of those studs (although it was out of plumb, so there's about a 1" gap at the bottom).

Front Wall Construction

I’ll bolt the inner wall, too, but haven't gotten to it yet (have to find the stud behind it and drill, then use some kind of toggle):

Inner Wall at Front

I'm tying the rim joists to the top plate with Simpson TA9ZKT staircase angles every 5':

Simpson TA9ZKT

up vote 1 down vote accepted

We worry about verticals loading AND horizontal loading. Resting the joists on the double top plate works great for vertical loading and using hangers to keep them aligned until the loft floor sheathing is installed is a great idea, because you can’t end nail them through the rim joist. (A cheaper clip, like Simpson’s A34 or A35 on one side of each joist would work too.)

However, I’d worry about 1) spacing of the joists, 2) securing that overhead load to the vertical supports (stud wall), 3) keeping the loft from rotating or moving away from the main building.

1) You said, “above you office”, so it’s not residential storage. The Code requires a minimum of 125 lbs. per square foot for light loads and 250 lbs. per square foot for heavy loads. (See ICC Table 1607.1.) That means those 2x6’s need to be 12” oc to span you 8’ loft.

2) You don’t have to design against wind loading, because you’re inside another building. However, depending where you’re located, seismic loading could be severe and you can’t rely on toe-nailing to secure the loft framing to the studs.

I’d use either a clip from the joist to the top plate or studs at about 24” oc or I’d use plywood sheathing to hold the joists to the top plate (and keep the loft framing rigid...but more about that in item 3) below. )

When you have a lot of weight up in the air, an earthquake can get (and keep) it moving. Gypsum board (wallboard) can resist this movement, but it’s fairly weak. OSB board or plywood is much better. If you told me you were going to store your Christmas decorations up there I’d thing gypsum board would work. But if you are putting books, dead files, or that old transmission you were going to fix someday, up there, I’d worry....then you’re well into the 250 lbs. per square foot.

3) The whole loft needs to be rigid enough to keep everything in the loft off your head while you’re preparing your will. I like 1/2” plywood nailed at 6” oc to all WALLS and all supports, including the loft rim joists. That way you solve item 2) above, and item 3).

Fastening the office and loft to the main building is a good idea, but I’d need more info on type of building, height, material, etc.

  • I edited my question with some description of the building construction. I do have OSB on the partition wall to provide side shear protection. I think the existing side wall probably has thin-gauge steel studs, not sure how strong it will be for the purposes of anchoring my structure to it. I will also put 3/4" plywood on top of the joists. – Rick Dec 3 '17 at 9:43
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    The 3/4” plywood will be plenty stiff for a floor for your loft. If you notice the grade has a 24/48 in it. That represents the maximum spacing rating. That is: floor / roof, if you install the long edge of the plywood perpendicular to the joists. – Lee Sam Dec 3 '17 at 16:01
  • Not sure I understand the 24/48 grade you mention. I also have run into a question about how to fasten the rim joist to the top plate along the existing wall; there's a 1" gap between it and the wall, making it hard to hammer into the joist hangers. Perhaps I should ask a separate question about that. – Rick Dec 3 '17 at 23:28
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    I’m just saying the 3/4” plywood loft floor sheathing is fine. So, after the joists are secured to the rim joist, then secure the joist to the INSIDE of the double top plate with Simpson A34 or A35 clips at about 48” oc along the top plate. – Lee Sam Dec 4 '17 at 2:00
  • Thanks! I ended up using Simpson LUS26 hangers against the rim joist, Simpson TA9ZKT Staircase Angles between the rim joist and top header plate (see photo added to question), and was considering Simpson H1 hurricane ties between the joists and the double top plate. – Rick Dec 5 '17 at 2:18

I see no problem with that. The wall below takes all the weight. All you need is something to keep the joist in place and from falling over. Hangers would certainly do that.

You can end nail the joists--by building the ceiling with the rim board away from the wall (e.g. 24" out) and then sliding the ceiling (rim board and joists end nailed from the block wall side) up to the block wall.

  • Oh, this is smart. I wish I’d thought to do this. – Rick Feb 10 at 18:12

I think I'd just build the roof as though it were another wall. I would use screws instead of nails on the joints against the shed wall, and then I would screw the plate into the shed wall.

Like Paul said, there's very little force at play here. The drywall or other sheathing on the walls of the room are going to provide plenty of diagonal bracing. You're just looking for a little attachment to the shed wall to keep things tight.

Hangers are the way to go with this, but be sure that you are toe-nailing the rim joist, and I'd recommend toggle-bolting the rim-joist to the concrete block wall, if it is concrete block, for structural stability of the whole build.

  • The rim joist is up against a sheetrock wall with (I believe) metal studs. The back wall (opposite the roll-up door) is cinder block. – Rick Nov 23 '17 at 6:12
  • So screw the rim-joist into the metal studs - should be easy to find with a stud-finder. Just watch out and use it on yourself when women are around - they hate that kind of joke. – Jim Cody Nov 30 '17 at 16:26

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