While I was browsing the Simpson web pages, I found that whereas they advocate their 1/4″ “strong drive” wood screws for structural applications, they specifically advise *against* lag screws.
This starts to make me nervous, since my carpenter sistered my 2×10 joists with 3/8″ lag screws (about one every 2-3′). To add to my nervousness, I’m seeing cupping of the sisters and separation of joist and sister at two points. There is a steam pipe going between the joists in question, but it’s insulated.
I’m wondering if I should go in with some carriage bolts and try to stop any further separation. Alternatively I’m worried about weakening the joists with too much fasteners; in my enthusiam, I nailed the hell out of one joist and introduced some splits…. I’d like to add blocking in some joist bays, but I’d rather not go crazy unless I have to…..
Replies
I think Simpson is primarily interested in 2 things.
First would be selling more of their own stuff.
Second would be stuff like fastening girder plies together and stuff like that.
Personally, I like through bolts and washers much better than lag bolts - It draws stuff together much better.
Sistering joists isn't all that big of a deal, so lag bolts don't concern me much.
Let me add to what Boss Hog said,
I would put through bolts with big washers in the joist that are cupping. If the centers are tight and the gap is at the top and bottom then start with the first bolt 2- 1/2" up from the bottom. Go 3 feet away and put the next bolt near the top of the joist. Continue staggering the bolts all the way down the joist.
If the cup is gapped in the middle just put the bolts down the middle or wherever there needed.
I usually drill the holes as small as possible for the bolts. This usually requires me to break out my new douglas hammer to "tap" them in, so I don't mind.
I agree with Boss Hog too.
Sistered joist don't really have to be nailed together. They'll each independently hold up their share of the weight. nailing them together might gain some additional strength, but I hardly would lose any sleep over it.
I WOULD NOT drill holes 2.5 inches from the edges. That WOULD weaken the joists. I'll let the engineers say why, but no holes should be drilled anywhere but in the middle third.
blueWarning! Be cautious when taking any framing advice from me. Although I have a lifetime of framing experience, all of it is considered bottom of the barrel by Gabe. I am not to be counted amongst the worst of the worst. If you want real framing information...don't listen to me..just ask Gabe!
Why are you putting any screws at all was it on the plans? The 2x10's can handle the span by themselves. You can put some nails into the old joists but that's all you need. I've only seen it done once before and that was about 20 years ago but it was the builders choice but that was the only time. Your probably going to have a lot of nail pops trying to use 3/8" lagsbecause you said that they're already cuping and seperating.
If it's not on the plans your wasting your time. What is the span anyway?
Joe Carola
The original joists go the length of the house but were butchered to hell by plumbers (this is in a bathroom reno). The sisters were attached to level the floor and strengthen (what's left of) the joists. They are notched to sit on a ledger, like the original joists, where they meet the outside wall. At the other end there's nothing to attach them to except the joists they're parallel to. So those lag screws, plus some 16d nails (not many) are mainly what's holding them up.If there are some lag screws attached within 3" of the top of a joist (this happened on a couple, where 2x4s were attached to a sister to reduce a span) I assume blocking will mitigate the damage?Edit: The span is 5-1/2', it's just a bathroom. My understanding was you use carriage bolts for sistering, otherwise you get squeaky floors later from nail pops. But the carpenter used lag screws instead.
Edited 11/17/2004 8:13 pm ET by Taylor
Taylor, I can't say for certain without seeing your bathroom first hand, but it sounds like you may be getting lost in the details. How long's this bathroom remodel been going on now anyway? Time to get that floor closed back up and move things along brother.
FWIW, I disagree with Blue's statement that sistered joists need not be fastened together. Carriage bolts if the engineer specs 'em, but the rest of the time it's just three gun spikes every sixteen inches or so. Done. It's the same concept as built up beams..... if those need to be fastened together (we DO all agree on that one, right?) sistered joists fall in that same category.
"Time to get that floor closed back up and move things along brother. "Roger that.
thats the easy way out...its called "procrastenating"
"Carriage bolts if the engineer specs 'em, but the rest of the time it's just three gun spikes every sixteen inches or so. Done."Tried that when I tried sistering myself [that sounds vaguely illegal], 3 16d nails @ 24oc. Wood split. On a major load-bearing joist, that'll put the fear of God into you.Carriage bolts weren't spec'ed by any engineer. Someone told me that nails will result in squeaky floors. Asked the carpenter to use carriage bolts. He used lag screws with glue instead. Now I'm getting nail pops, and I don't even have the floor down.If I can get the lag screws out, I'll retrofit carriage bolts.
Taylor...there isn't any such thing as a "major load-bearing joist" . A joist carrys 16" of floor load.
A beam can be "major load-bearing" beam. Then, you would need to pay attention to fastening requirments.
blueWarning! Be cautious when taking any framing advice from me. Although I have a lifetime of framing experience, all of it is considered bottom of the barrel by Gabe. I am not to be counted amongst the worst of the worst. If you want real framing information...don't listen to me..just ask Gabe!
I do alot of rotten wood repair in this area, which often involves cutting out sections of what used to be floor joist, and sistering in new ones. I always use 4 - 8 carrage bolts on each side of the splice, depending on the load on the joist. It may be overdoing it, but it's one less thing to ever have to worry about agian.
I'd say if youre worried about the lag bolts, put a jack under the joist to press it back up, slightly, and replace the lags with carrage bolts,- one at a time.