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SpaceCadet 01-17-2019 01:50 PM

Is there a better choice of fastener? There's these but they seem a bit excessive: https://www.homedepot.com/p/Simpson-...RC50/100375298

I've got a cordless drill with a clutch that's been my driver. The star drive helps for sure. Predrill for each one. My planned spacing is 2 screws, a screw 1.5 in from either edge every 8". I'll dig through the pile to find relatively dry ones with fewer knots and straight edges.

ss3964spd 01-17-2019 02:04 PM

Either many small diameter fastener, or fewer large diameter fasteners.

Star drive heads help. But if you can justify a new tool an impact drill/driver will make you wonder how you've managed to live this long without one.

And it's probable that you wouldn't need to pre-drill if you had one.

Clamps sure will help.

wwhitney 01-17-2019 02:59 PM

Ideally find a local lumber yard that stores their KD material covered.

If you like SPAX I suggest any of their 1/4" x 3" powerlag varieties.

Cheers, Wayne

SpaceCadet 01-17-2019 05:54 PM

How about Simpson Strong-Ties? https://www.homedepot.com/p/Simpson-...RC50/100375298

I picked up some spruce 2x8s so I have something. They're drying in the basement now. The lumber yard stores them under an awning outside and the quality isn't that stellar. I'll check out a few other places for something better.

Also can I sister on both sides of a joist using 3/4 plywood instead?

wwhitney 01-17-2019 07:14 PM

Plywood is not a good choice, as only the plys with grain parallel to the joist's grain will contribute to bending strength. So a maybe 3/8" thickness for 3/4" nominal plywood. Plus often the length is only 8'. If you want a manufactured product, use an LVL.

Those Simpson HDG SDS screws you linked to would probably work, although you don't need HDG, and the screws are designed for metal to wood connections, so I'd suggest using washers. A 3" Simpson SDWS would be a more appropriate choice. I kind of like the SPAX Powerlags myself.

Cheers, Wayne

SpaceCadet 01-18-2019 12:06 PM

SDWS is strong-drive wood screws? Is this it? https://www.homedepot.com/p/Simpson-...-R25/203302236 Look good but they're not in stock around here.

How about these: https://www.homedepot.com/p/SPAX-1-4...0757/202041033 or is the star drive washer head better, this one here: https://www.homedepot.com/p/SPAX-1-4...0767/202041026 Wish they were sold in boxes instead of individually!

I called the 4 nearest lumber yards and they all just have framing grade #2 or better SPF that they keep outside. The ones I bought yesterday have been resting in the basement and one of them is already curved up. At least they seem reasonably dry. The only place that claims to have anything better (select or douglas fir) is home depot. I can order LVL for x4 the cost of SPF. I can probably swing that if it'll make for a sturdy floor, is it worth it? Is looking for kiln dried douglas fir worth the trouble?

ss3964spd 01-18-2019 01:58 PM

KD lumber is going to be easier to work with Paul; lighter and easier to cut than anything wet. Again though, you don't need it to be pretty in your situation. I've read, generally, LVL's of the same dimensions as your joists will be stronger, flatter, straighter, and every other "er", including pricier. And over kill, IMO.

IIRC, you're just trying to beef up joists that are just barely short of meeting deflection standards for ceramic tile. You could probably get them above that L target using 2X6's as sisters.

wwhitney 01-18-2019 03:13 PM

Paul, that latest HD link you provided is still to SDS screws. Here are SDWS screws:


My HD carries these:


Using 10d common (0.148" x 3") nails would be cheaper and quicker if you have a framing nailer. They just won't draw the joists together, so you'd need to take other steps to do that, e.g. temporarily clamp them together.

There's been no discussion so far of nailing pattern. The 10d nails would require maybe 2 rows, each row 1.5" from the edge, 12" o.c. in each row? Not 100% sure on the proper spacing within each row.

Cheers, Wayne

SpaceCadet 01-18-2019 04:27 PM

I try to use screws whereever possible and predrill. The old wood is brittle and I don't want it to split any more than it has to. I haven't got a nailer but I do have something that drives screws. I was leaning toward the SPAX 3" washer head powerlags. What would you suggest for pattern for these?

I'll probably go with the regular SPF lumber. Just frustrated that I can't find better stuff. The best 2x8s I dug out of the pile aren't even as good as what I'm used to for 2x4s. Cracks and knots and of course stored outside.

Thank you for all your help.

wwhitney 01-18-2019 07:09 PM

For the edge spacing, I'm not sure if 1" or 1-1/2" is the better choice.

The reference design lateral value for a 10d common nail joining two 2x members of specific gravity 0.42 (SPF) is 100 lbs, while for a 1/4" x 3" Spax Powerlag it is 185 lbs per their ESR. So whatever the proper spacing for 10d common nails would be, you can space the 1/4" x 3" Spax Powerlags about 1.8 times as far apart.

Cheers, Wayne

SpaceCadet 01-20-2019 07:01 PM

3 Attachment(s)
Started pulling down the plaster ceiling in the basement below the bathroom and found this lovely terrain feature:
Attachment 206612
This is one of the doubled-up joists below the wall that holds all the plumbing. I had noticed that it's a bit warped and cracked when I was putting in the blocking under the toilet but nothing this bad. It looks like it's dried and cracked about half way through. I don't see rot or insect damage but there are some water stains around so that may have contributed.

The good is that the sister joist looks to be in pretty good shape. There are some minor length-wise cracks.
Attachment 206614
They are nailed together with what could be a 16d nail every 12"-16", mainly at the top. They look like they're mostly in alignment and the cracked joist mainly hangs below the good one in the vicinity of the big crack. The load should be distributed fairly evenly, the floor boards mostly run across both. I haven't had a chance to check everything with a mason's line.

The bad is that there's a lot of stuff adjacent and attached to the cracked joist:
Attachment 206613
It's holding blocking, one of which holds a partial-span joist, and there's plumbing. I could add a sister up to the blocking but there's a water pipe in the way so a 2x8 won't fit. I could probably fit a 1x8 up to the blocking, add a 2x8 on the other side, glue, drill and bolt with washers. I don't really want to drive screws into the cracking joist. Sandwiching both joists between new wood seems safest. Extra structure shouldn't hurt, there's a granite countertop and dishwasher right next to this.

Any advice?

wwhitney 01-21-2019 09:06 AM

A couple questions:

That header (blocking) the sistered cracked joist is carrying, how many joists is the header carrying, and is the other end of the header also carried on a sistered joist?

How far is the crack from one end of the joist, and what is the total span?

Initial thoughts:

If the sister is there to repair the crack, and if the crack is not in the central 2/3s of the span, then possibly you don't need to add an additional joist. The sister joist should be strong enough for the load, and if the cracked joist is continuous for the central 2/3s of the span, then it is still helping stiffen the sister joist.

However, if the header is carrying multiple joists, then the sister is there to pick up the additional load imposed by the header. This would be reflected in the other end of the header being carried by a double joist. Or if the crack is in the central 2/3s of the span, the cracked joist isn't helping stiffen the joist as much as it should. In either case, it would be a good idea to add a third joist, it doesn't matter which side it is on.

Cheers, Wayne

SpaceCadet 01-21-2019 11:54 AM

1 Attachment(s)
I drew a quick sketch of the layout. Some of the measurements are approximate. I checked the sag of the intact sister with a line and it looks like it's sagging about 1/2" in the middle.
Attachment 206622

The header is carrying only one joist and the other side of the header is also attached to a sistered joist. The crack is 4 feet from the end of the cracked joist. Total span of the joists is 12 feet (11'4" between sill and beam that their ends are resting on).

Reasonably certain the sistered studs were part of the original construction so it's the 2nd scenario and I'll need to reinforce. When you say another joist, do you mean a whole other joist with the ends resting on the sill and center beam or can I just scab it on? The sill and center beam have bricks and mortar on them (I assume for fire-block) that I would rather not mess with and I'm afraid jacking up the joists to straighten them will crack the finish on the walls above.

How about: 11' 2x8 on good sister side, 7' 1x8 on cracked sister side (from beam to header), PL premium and Fastenmaster Thrulok alternating top/bottom every 12" (https://www.homedepot.com/p/ThruLOK-...INDY/204307982). Secure header to 1x sister with L-angles (https://www.homedepot.com/p/Simpson-...L26Z/202071149). The thruloks will clamp everything together, if I pre-drill they won't stress the wood for splitting, and they're thinner than carriage bolts. The 1x sister isn't as strong but maybe helps spread the load from fasteners.

All the other joists, including the short one are also getting sistered but I'll just use lag screws for those.

wwhitney 01-21-2019 09:58 PM

From your drawing, if the header is only carrying one joist, then the "king" joists didn't need to be doubled in the first place. So it is somewhat overbuilt, which is to your benefit. Given that, I think it will be enough to sister all your single joists (including the short one), add fasteners to the existing double joists at the same schedule, and then do something to repair your cracked joist.

If you don't care that the cracked joist has sagged, you can just splice on an 8' piece of joist, centered over the crack, and then use "alot" of 4.5" fasteners on each side of the crack to connect the splice. Not being an engineer, I don't know the proper value of "alot", but I would say somewhat more that you are using for normal sistering, maybe 50% more?

If you want to address the apparent sag of the cracked joist (it looks like it has sagged relative to its partner joist), then you'll need to jack it up before attaching the splice. If it is nailed to its partner joist in a way that prevents it being jacked up, you'll need to pull a few nails to allow that to happen.

Cheers, Wayne

SpaceCadet 01-22-2019 07:51 AM

Two questions:

The cracked joist looks like it's sagged relative to the intact one at the bottom but only within a few feet around the crack itself and they both look flush to the floor boards at the top. I thought this is because the cracked joist has frayed and expanded over the cracked region. I'm reluctant to jack up the floor but is there any benefit to jacking up the cracked wood to try to compress it back together or should I just leave it or shave it flush?

There is plumbing in the way of putting up even a short sister on the cracked joist's side. I would have to cut and reroute some of it just to get a 2x8 up there but I could probably fit a 1x8. Does that have any benefit if I also add a 2x8 on the other side and tie it all together? I'm not ignoring what you said about the already sistered joist, I'll call the plumber to cut the water lines so I can get a 2x8 on the cracked side if I have to but overbuilding seems like erring on the side of caution.

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