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Unread 01-22-2019, 08:09 AM   #31
ss3964spd
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It's difficult for me to see if those CI drain lines are too close to get a 2X8 between them and the cracked joist, Paul, but if there is space my inclination would be to cut the water lines, temporarily support that one short joist that ends at the header, remove that header, sister a new 2X8 to the cracked one, install new header, fasten short joist to new header (you could use joist hangers for both the header and joist).

If the water supply lines are feeding only the bathroom you're working on you could shut the water to the house off, cut the lines yourself, install some temporary compression fitting stop valves, turn water back on. That buys you all the time you need before bringing in a plumber to fix the lines.
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Unread 01-22-2019, 09:32 AM   #32
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Dan, I agree and that's what I'd like to do but there isn't enough room for a 2x8 for a full span. I annotated the picture I had in a previous post:
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The bigger farther one, made of cast iron is right up against the joist and actually tied to it right behind the header. The closer in one is about 2 inches away from the joist but there's a copper line that's behind it that wonders in too close for a 2x8 to fit (but would fit a 1x8). It could be moved but I'd want a plumber to reconnect it and it supplies hot water to the one working bathroom upstairs. So I can't really go past the header with any size sister and if I want a 2x8 on the cracked side I have to get the plumber to come in at the end of the day and reconnect lines that I cut in the morning to get the sister in place that day and hope that nothing goes wrong as I install it. That said, if I have to do it, I have to do it. A lot of those valves could use a replacement anyway.

On the other hand, all that's on the other side of the twin joist is some wiring and blocking that I could remove and reconnect that pretty easily. This is why I'm talking about putting most of the reinforcement on the good joist side and just running something weaker on the cracked joist side as something to keep fastener heads from cracking the fragile joist and an attachment point for the header. I don't mean to be difficult and you guys are giving me incredibly helpful advice but there are some factors that may not be readily apparent.
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Unread 01-22-2019, 09:38 AM   #33
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(1) Your theory on the crack causing the bottom of the joist to be deflected without affecting the top of the joist looks reasonable. If you wanted to be fancy, you could try repairing the joist by injecting the open cracks with an appropriate formulation of gap filling epoxy, and then jacking the cracks closed to the extent possible and letting it cure.

Another reasonable repair, if the upper half of the joist is undamaged, is to do the above with regular wood glue, not so much to fully restore the joist but to bring it back to the original dimensions. Then you can repair the bottom (tension) side of the joist by fastening a thick metal strap along the bottom.

(2) Now that I blow up your last photo I can see the crack's location relative to the plumbing. A few thoughts:

You could use a 1/4" thick steel plate in lieu of a 2x8. This would get fastened with SDS screws, and wouldn't need to be as long.

Something makes me think that the 1x8 is not worth it, but if it is properly fastened to the joist it would help. And as far as I know, it would be fine to put the 2x8 on the opposite side of the double joist.

Cheers, Wayne
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Unread 01-22-2019, 10:43 AM   #34
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Not being difficult at all Paul, forums like this are absolutely wonderful for getting feedback and ideas one may not have considered on their own. My bacon has been saved many, many times by folks who contribute.

IMO, that crack...the extent of it, renders that joist all but useless. My guess is that header is nailed only through that cracked joist - not through both. Easy to confirm though, just look for nail heads on the side of that sister that align with the header. I can't see how solidly that cast iron drain pipe is connected to the cracked joist, but you probably don't want to disturb it, least you create a leak in the hubs. Also can't see if any of the ends of the floor boards above end on that cracked joist or if they extend past it onto the good joist.

I also agree that a 1X (3/4") probably isn't going to help much. Given the constraints, I rather like Wayne's idea of a steel plate.
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Unread 01-22-2019, 11:11 AM   #35
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If you lay a straightedge on the floor above the cracked item, is it flat, or is there a depression? Is the subflooring tight to the joist, or is it suspended above it?

If you end up trying to jack things up, you'll need to do it over time - probably at least a couple of days or you may crack other things above. The wood acts like a spring for short duration loads, but long-term, it literally 'flows'. It doesn't want to flow back easily. You can see a similar effect in a shelf on a bookcase that isn't well supported...it will get a big bow in it. Remove the load, and it will stay sagging if the weight has been there long enough. Turn it over, reload it, and it will slowly bend back and eventually sag the other way.

Interesting side note...scientists have come up with a way to treat wood so that they first soften it, then compress it to take all of the air spaces out of it. The end result once it dries is that it's stronger than steel and weighs less! It could even make it into structural components in a car sometime in the future and would sequester carbon in the process.

I haven't investigated LVL material, but they may make some that would have the needed strength that would fit in the space you have.
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Unread 01-22-2019, 11:26 AM   #36
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Pretty sure the header is only attached to the cracked joist. It's toe-nailed to it, you can see the nails in the photo. If it's nailed through the joist from the other side, I don't know, but I dont' see nail heads in the good sister. There's a nail through both joists near-by, they're nailed together every 12-16". There's some floor boards and blocking attached to that header on the other side. I could probably trim it short of the cracked joist to fit in a sister but that doesn't seem worth the effort when I can run the sister up to the header and attach them with a metal bracket instead.

The cast iron pipe is pretty solidly attached with a metal loop nailed on through an additional 1x. If I removed all that, there might be room for a metal plate or another 1x but a 2x8 is out of the question, and anyway, like you said, I don't want to mess with that. The floor boards run over both joists in that area. There's a few farther down toward the sill that I replaced that rest only on the cracked one.

I saw some information about flitch plates. Is the metal plate approach you're talking about different? I heard they need to be sandwiched between lumber so they don't buckle. Where would I get a plate like this? The 2x8 sounds less tricky.

Jim: The flooring above is old planks nailed to the joists. They seem to be tight against the joist. These particular joists are below a wall but there's plywood glued/screwed to the planks. The bathroom above is only as far as plywood on the floor but the walls are finished drywall and cement board with waterproofing on it. I'm afraid if I start jacking it up the finished walls will crack. I should have done this while everything was down to the studs but I was under the mistaken impression that the structure was good enough. The bottom of the good joist sags ~1/2" relative to the ends but the floor above, while uneven, is reasable, maybe within an 1/8 or so over 4". Flattening that out with feather patch was going to be the next step before this whole thing came up. I'll check it again tonight.
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Unread 01-22-2019, 11:52 AM   #37
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Given the loads it's going to see I don't think a 1/4" steel plate would buckle if it were fastened correctly. But I don't know for certain.

Perhaps another option: jack up that cracked joist, slowly as Jim mentions, and keep it supported. Slap as long a sister as you can to the good joist and fasten as necessary Drill 3/4" holes through them all - nice and straight, but staying, say, 2" back from the crack on each side, 4 holes on each side of the crack, spaced maybe 8 to 10 inches apart and making sure no hole is in line either vertically or horizontally. Use threaded bolts (not lags or carriage bolts) with washers on each side. Crank those things down.
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Unread 01-22-2019, 12:26 PM   #38
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Simplest may be to abandon the cracked joist in place. I.e. leave there, don't count it in your joist structure, and make sure any structural connections don't depend on it.

So you'd secure the header to the intact joist with 3 6" lag screw equivalents (e.g SPAX T-star Flat Head) driven flush from the exposed face of the intact joist into the end grain of the header. Then you'd sister that intact joist for its full length to get the stiffness you want. [Getting bearing at the ends would be nice, but isn't necessary.] Finally you can fasten the cracked joist to the assembly with the same pattern as the sister, just to secure the cracked joist and anything else attached to it.

So no jacking to disturb anything, and once you've done the above, no reason not to shave off the bottom of the cracked joist where it is in your way.

Cheers, Wayne
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Unread 01-22-2019, 12:54 PM   #39
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Quote:
Use threaded bolts (not lags or carriage bolts) with washers on each side.
Dan, did you mean threaded rod? The idea of drilling 3/4" holes through that joist scares the crap out of me. Or is the wide curvature intended to reduce stress and stop cracks?

I was eyeing these Fastenmaster thrulok's: https://www.homedepot.com/p/ThruLOK-...INDY/204307982 Self-drilling fastener and washers all in one.

I'd probably still pre-drill but they're a bit less than 1/4" thick.

Even with the washers, I'm worried that the fasteners will crack the dry joist. That was why the 1x8. Or would it be pointless as an extra layer of padding?
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Unread 01-22-2019, 01:44 PM   #40
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Then use more, but 1/2" bolts and nuts. What I like about the heavier duty hardware is you can tighten it much more which will draw the faces/grains of the 2X's hard against each other.

Honestly though, I don't think you'll have a cracking issue. I had to bolt together 5 sets of 40 YO 2X10 joists very near their ends for my bathroom project not a single one cracked or split. Don't have a clear picture of the my 3/4" bolts but they're right where the joists lap each other.

And like Wayne says, you're effectively taking that cracked 2X out of the picture as far as it doing joist duty.
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Unread 01-22-2019, 02:03 PM   #41
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Something like this? https://www.homedepot.com/p/Crown-Bo...0680/100147536

My joists are 70 years old but I get what you're saying. I'll use big washers.
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Unread 01-22-2019, 02:07 PM   #42
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Or, you could take out a 12" to 16" section of it where the crack is, and header off both ends to the good joists to the left and right, and then sister those. You'd have to deal with the electrical lines though.
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Unread 01-22-2019, 02:28 PM   #43
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Wayne: How do you feel about GRK? I've been impressed with them in the past and they have these 5/16 x 6 in screws: https://www.homedepot.com/p/GRK-Fast...6015/204837519

Dan: Do you mean cut through both the cracked joist and its sister, sister the next joist over then header over to those? That sounds very elaborate and then I would have a long unsupported span of floorboard. And either a joist segment that's attached to headers on both ends or a header attached to a joist that ends in a header.
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Unread 01-22-2019, 09:13 PM   #44
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Checked the floor above. It's a small area a bit less than 6 feet between door and tub, 5 feet wide. It's within 1/16" measured perpendicular to the joists and dips 1/8"-3/16" around the middle of the area measured along the joists. So it curves along the joists.
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Unread 01-22-2019, 11:40 PM   #45
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I like GRK, not used them much but I think their reputation matches or exceeds SPAX. Not sure why you need a 5/16" x 6" fastener, though. Plus it seems a bit pricey.

I'm of the school of thought of more, redundant, smaller fasteners, rather than fewer larger fasteners. The big bolts would draw things together easily, but that can also be done with clamps prior to install the smaller fasteners.

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