Uneven joist widths

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Old 09-23-15, 05:32 AM
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Uneven joist widths

Just mounted my joist hangers and joists. Right now only the hangers are attached to the ledger.

I ran a string line off the edge joists and got the tops just barely touching and secured one side. Plumbed and secured the other.

I took out the joists to flash them (Vycor membrane) and realized I missed my lower layout line by 1/4 to 1/2" on about 3 of the 8 joists. Upon further investigation, it seems those three are closer to 7-1/2 or 7-3/8" wide instead of 7-1/4". It's all been acclimating for a month, stickered, etc. Those boards felt wetter than the others as well.

So I can either leave the hangers as-is, but then I worry about if those shrink and I have a low spot in the deck.
OR
I can rehang the hangers so it settles down to the other level eventually but have a high spot in the deck (which I'll put the crown in the middle). But if they don't shrink as much there will always be a high spot.

I have the boards sitting up on sawhorses now so they can hopefully dry out more today, but I can't wait two weeks to keep this moving.

Any advice? Thanks,
Anthony
 
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Old 09-23-15, 06:55 AM
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Joists

Your description is not real clear.

Are the top edges of the joists aligned with the tops of the beams/ledger at the ends of the joists?

And do you have the crowns up on all joists?

Please clarify your question.
 
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Old 09-23-15, 07:17 AM
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Hi arc2v,
Here's what I got from the post, perhaps because I've been fooled many times by the actual dimensions of 2x material. Sounds like you placed the hangers anticipating the joists would be 7.5 inches high and then discovered they are less and worse, varied. As a note, always check your material and size for the smallest. Anything over that can be trimmed a bit where it rests in the hanger.

I assume you don't want to remove and reposition the hangers, so shimming is all you can do, besides returning that material and looking for all 7.5" boards. When required I use a shim that will not degrade being outside. Some of the synthetic materials work well.

Bud
 
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Old 09-23-15, 07:35 AM
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Sorry for confusion.

Here's what I did.

1) marked crown up and best factory end of each joist
2) Put "shelf" below the ledger to rest the joists on (but not in perfect position). Shelf was also my story pole to show joist location.
3) Picked two best joists and set them carefully on each end of the ledger.
4) Ran string line between the two end joists

5) Clamped hanger onto end of joist to hold in place. Shimmed until top of joists is barely touching string line and secured one side of the hanger.
6) used level to make sure the joist is plumb and secured other side. Double checked and then set remaining screws.

When I pulled the joists out, I notices that 3 of the 8 were below my bottom line for alignment (which I could not see with the joist in place, in retrospect, I should have extended it farther out).

So if I leave everything as it is now, the tops of all joists will touch the string. But then may sag as the board dries out.

If I move the hangers up a bit so the bottoms are lined up, then the deck will be higher at that point and *hopefully* will settle down as the board dries out.

I hope that's clearer. Sadly the pictures are at home now, or I'd post some.

Thanks.
 
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Old 09-23-15, 07:36 AM
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I gather part of the OP's concern is some of the PT joists are wetter than others--even after a month on-site. Will they continue to shrink and eventually end up level without shimming?

This is a concern with using PT framing that isn't normally discussed in the usual how-tos. Sort through a stack at the home center and some will be very wet and heavy, while others will be dry to touch and much lighter. If you have your materials delivered you have no control over how "ready" it is to use.

ETA: OP clarified. I type slow...
 
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Old 09-23-15, 07:52 AM
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Thanks Guy. You got it.

I had my lumber delivered from a local yard. Most were in excellent condition (I've only had to discard one board so far), but the moisture level here is probably what's in play. It wouldn't be impossible to get more boards, but it would be a pain. Plus these boards are straight, just wider than normal.

The swollen boards are noticeably heavier. Easily 5 pounds or so more than the drier ones. (8' lengths)

Anthony
 
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Old 09-23-15, 04:11 PM
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Your mistake was putting joist hangers on first. Not sure how everyone else does it but I will toenail the joist, flush the top with the rim or ledger, then come back and put hangers on after all the joists are tacked up.

On a floor, the surface is what needs to plane out, so a "bottom line" is kind of backward.
 
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Old 09-23-15, 05:15 PM
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Bottom marking was a nominal location based on the plans. Hangers were set with the actual joist in there up to a top string line. My worry was what would happen when the wetter boards dried out more.

I measured all boards and found most were within 1/16 of 7-1/4. I had one bad outlier at 7-7/16, so I discarded it and used another board. That was one of the hangers I set that was way off.

The other hanger that was off was 7-3/8 on one side, but was 7-1/4 at the other end, so I flipped it and redid the hanger.

Still might have some problems as things dry out, but they are starting a bit better and the problem boards are next to each other, so it will end up being a slight dip instead of a wavy surface.
 
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Old 09-24-15, 12:18 PM
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Is there a "correct"?

Install the hangers first--uniform dimensions, easy to align. Joists "should" end up at proper dimension once dried out.

or

Install joists one at a time so all are flush to top of the ledger (or string) and maybe some will shrink and cause dips on the level?

*OR*

Who cares? You're using PT because it's an outdoor deck and nobody expects a ruler-flat floor.

I'm not being obstinate--I'm just wondering if either method has it's drawbacks and in the end it doesn't matter enough to choose one over the other?
 
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