if you look in simpson's specifier book, #8 3" screws are acceptable in many of their connectors.. 3" sheetrock screws are #8, BTW. the nails you get today are no better than sheetrock screws, and hold much worse.. I can't tell you how many times I've pulled the head off of a 8d or 16d nail trying to pull them out.. ****, I've even had the heads fall of 8d nails when nailing in Simpson H10 and H2.5a connectors, sure makes me feel good.. not. take a wrecking bar, drive a 3" screw in 2" and try and pull it out. chances are when the screw actually does fail, you'll end up on your derriere from the amount of force you're exerting on it.
sistering floor beams
- Thread starter JHZR2
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if you're going with the plywood method, you need to provide a uniform clamping force for the adhesive. bolts at either end aren't sufficient. nails will work, but you'll need to tighten the pattern to 3x3 or so, as nails don't hold anywhere near as well as screws.
do you have a picture of the beam?
JHZR2
Staff member
Regardless of the method I choose... bolts at either end AND nails/screws throughout... was what I meant.
OK, so probably Id do a 3x3 pattern whether I use plywood or an equivalent size piece of wood with nails.
And you said 4x4 above if using screws.
However, shall I use drywall screws, or are wood screws or similar the smarter choice...
Maybe its just preference???
If predrilled, I assume sheetrock screws will go in well... but would wood screws be less prone to snapping heads? I dont mind a little overkill...
Thanks,
JMH
P.S. Pics hopefullyon the 28th.
OK, so probably Id do a 3x3 pattern whether I use plywood or an equivalent size piece of wood with nails.
And you said 4x4 above if using screws.
However, shall I use drywall screws, or are wood screws or similar the smarter choice...
Maybe its just preference???
If predrilled, I assume sheetrock screws will go in well... but would wood screws be less prone to snapping heads? I dont mind a little overkill...
Thanks,
JMH
P.S. Pics hopefullyon the 28th.
I would have thought that fabricating a "flange" and attaching it to the underside would be even stiffer that sistering a beam next to it.
That's what I intend to do under my house to reduce cracked tiles (never knew kids could make a floor move so much).
That's what I intend to do under my house to reduce cracked tiles (never knew kids could make a floor move so much).
it needs to be plywood, it's far stiffer than an equivelant piece of solid wood. I said 4x4 for screws, 3x3 for nails.
I prefer sheetrock screws, plain hardware store wood screws are made from some seriously crappy steel. I don't have a problem with snapping the heads off as long as I'm not trying to drive long screws into engineered lumber like LVL's or timberstrand.
what i gave you was an overkill solution.. so you're good there.
what's going on is the screws are used to provide a clamping force, so that the load is actually transferred by friction between the members. the adhesive is used to prevent the joint from becoming slip-critical and putting a shear load on the screws.
Drywall screws have very little shear force. If you are using it as a temporary clamp until an adhesive cures thats fine, but otherwise leave the drywall screws for hanging drywall. Your talking a structural component stick with bolts or lags. You have better shear force, which has been explained, with a common nail. The easy route would be sandwich it and nail the heck out of it with 10's or 16's.
I could hang your vehicle in air with 10 drywall screws. Jeez, I do re-hab construction for a living, gimme some credit.
My buddies and I pioneered using drywall screws to do framing, it's quieter to keep the building inspector from catching on to our activities. Yes, I would lay under a drywall screw with 200lbs of shear force applied.
Drywall screws can hold a large load, that's not the point, as the problem is that they're brittle and prone to 'unpredictable failure' from high loads experienced during assembly or in service. Fasteners in a range of brittle to 'normally ductile' would might go from drywall screws, case hardened deck screws, stainless deck screws, high grade bolts, lower grade bolts, wood screws, nails. At least use deck screws instead of drywall screws for structural members, even if they're not rated for such use.
any common stainless screw I've ever used were far softer than common steel screws, beit drywall, deck, wood or sheet metal. I really hate using them as the heads strip out or twist off at the shaft all the time, even if predrilled. they're no where near as strong as even a grade 2 bolt. stainless doesn't mean it's strong, just that it doesn't rust (as fast).
"...stainless doesn't mean it's strong, just that it doesn't rust (as fast). "
I agree, which is why I typically prefer tool steel or carbon steel knives. The advantage is that it's not as brittle as a drywall screw or some deck screws, so if the cross section is adequate you have a more reliable fastener.
I agree, which is why I typically prefer tool steel or carbon steel knives. The advantage is that it's not as brittle as a drywall screw or some deck screws, so if the cross section is adequate you have a more reliable fastener.
JHZR2
Staff member
OK, so we had the closing on the house... most stressful day Ive had in forever... and it went for a LONG time... dont know why it got so screwed up, but nobody was hearing anything from anyone for final approvals and so we sat and sat. All is well now.
I didnt get a chance to take a pic of the joists - I wish I had...
However, I noted one thing on the walkthrough: There are wires running through the joists in the centers... knob and tube wires and regular romex type wires that just got ran through the centers for whatever reason...
So I can't easily put a full size scab along the length, even just for a short run very close in to the compromised area.
So now my plans are this:
Get two long 2x4s, use 1/2" carriage bolts with big fender washers and construction adhesive, and put the bolts 1 ft apart (or perhaps 6in apart) in a staggered pattern (so long as the holes arent too close to the bottom of the joist). I can run the 2x4s as long as I want, and Ill put one right at the very top of the joist, by the floorboards that sit on it, and then one along the very bottom...
Since the major stresses are along the very top and bottom surfaces, it sems to me that a 2x4 with some serious bolts, extending out from the compromised point 4-5 feet would add stiffness and not compromise much in terms of putting newe holes.
Anyone think of any good reason why this would be no good? Seems it would add stiffness in the right places, and easily spread the forces along... with 1/2" bolts the hardware is VERY sound, so there are no screws vs. nails and materials issues.
WHat do you think?
Thanks!
JMH
I didnt get a chance to take a pic of the joists - I wish I had...
However, I noted one thing on the walkthrough: There are wires running through the joists in the centers... knob and tube wires and regular romex type wires that just got ran through the centers for whatever reason...
So I can't easily put a full size scab along the length, even just for a short run very close in to the compromised area.
So now my plans are this:
Get two long 2x4s, use 1/2" carriage bolts with big fender washers and construction adhesive, and put the bolts 1 ft apart (or perhaps 6in apart) in a staggered pattern (so long as the holes arent too close to the bottom of the joist). I can run the 2x4s as long as I want, and Ill put one right at the very top of the joist, by the floorboards that sit on it, and then one along the very bottom...
Since the major stresses are along the very top and bottom surfaces, it sems to me that a 2x4 with some serious bolts, extending out from the compromised point 4-5 feet would add stiffness and not compromise much in terms of putting newe holes.
Anyone think of any good reason why this would be no good? Seems it would add stiffness in the right places, and easily spread the forces along... with 1/2" bolts the hardware is VERY sound, so there are no screws vs. nails and materials issues.
WHat do you think?
Thanks!
JMH
2x4 has no load rating in the horizontal.
JHZR2
Staff member
I wouldnt be using it in the horizontal plane though, Id be using it on its 'side', vertical, parallel to the existing joist. Is there still no load rating?
OK, so if I can fit a 2x6, would this be OK???
Cutting wires would become a major project... I'm hoping that a good solution can be devised without having to do this...
WOuld just using a shorter 2x10, or an irregular size, like 1 ft on the one side and 3ft on the other, be more acceptable than my idea using 2x6's for a longer run?
Thanks again!
JMH
OK, so if I can fit a 2x6, would this be OK???
Cutting wires would become a major project... I'm hoping that a good solution can be devised without having to do this...
WOuld just using a shorter 2x10, or an irregular size, like 1 ft on the one side and 3ft on the other, be more acceptable than my idea using 2x6's for a longer run?
Thanks again!
JMH
JHZR2
Staff member
The notch is about 2-2.5"v x ~3"h on the bottom of 3 different joists. The holes for wiring are smack in the center.
Only one of the three has a wire hole in the center, so I can do it properly on the others.
There is about 4 feet on either side between criscross members of the center beam.
Thanks for the insight!!
JMH
Only one of the three has a wire hole in the center, so I can do it properly on the others.
There is about 4 feet on either side between criscross members of the center beam.
Thanks for the insight!!
JMH
Well then, you don't need anything on top of the joist, it is uncut and is in compression. On the bottom, the joist is in tension and does need some help. Of course it kind of depends on what kind load is directly above the the cuts. A 2x4 or 2x6 on one side of each joist should be enough. Whatever you can get in there. The bottom edge of the scab piece could even hang down below the bottom of of the joist. I had a similar deal on my current house, just one joist, but it was hacked in 2 places and was sagging right under the shower in the master bath. I used an 8' piece of 2x6. Before I installed it, I put a piece of 4x4 crosswise across 3 joists and used a small hydraulic jack to raise the joist as far a practical. When I jacked it, it wanted to twist so I installed 2 pieces of 2x8 crosswise between the next joists on either side to stabilize the joist. That was in 97 and haven't had a problem with it since. Hope that helps some.
The 2x4's, placed as you describe, will actually create a channel beam. A few uprights between the 2x4's will create a ladder beam with a closed side. You don't need all the bolts and washers, IF, you glue the add on pieces properly. Use nice fresh construction adhesive and lots of screws. Once the glue has aged out,the screws don't matter.
as for the wiring holes, if they are anywhere near the center, they don't matter. Just how big is the notch?/hole? you are trying to bridge? If a notch, is it on the top, or the bottom of the joist?
as for the wiring holes, if they are anywhere near the center, they don't matter. Just how big is the notch?/hole? you are trying to bridge? If a notch, is it on the top, or the bottom of the joist?
If you could get a picture up I can tell you exactly what you need to do. I work at a structural engineering firm and I deal with alot of wood framing every day. Depending on what part of the span these cuts are in you may not need to do anything. I'm just having trouble picturing exactly what is cut, where it's cut, and how much of it is cut out.
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