structural question - lag bolt length into stud?

[PoorOwner]

I bought something like this (48W" x 24"D)

it comes with 5/16" lags but 2.25" long. about 1/2 drywall so that leaves about 1.75", after bracket and washer, probably 1-5/8" into stud.

There are 2 brackets and 2 bolts per bracket.

Is it enough to hold 200 lbs something per shelf like they say?

I was thinking of grabbing some longer Spax or GRK RSS in the same diameter, but cannot decide if I would get 2.5" or 3" length.

 

[kaymccampbell]

As long as you have nothing running through the wall, like wires or pipes, then you can use 4" lags, but those ones that came with it, pretty much guarantee that you won't penetrate properly installed wires. And, I'm sure they'll work just fine for most folks. That said, GJ ain't most folks, so make sure you miss your pipes n wires n get the real long lags.

 

[couch67]

Cant comment on putting 200# on the shelf but I would bet the shelf would fail before the 2.25" lags pull out.

 

[mm08822]

Holding 200# means different things to people. 200# at the front edge of the shelf is different than 200# evenly distributed across the entire surface and still different than 200# distributed very close along the back edge (wall) of the shelf.

The shelf brackets shown provide very little vertical support as compared to ones that are taller. Taller however is a PIA b/c they get in the way placing stuff on a lower shelf. Deeper brackets are more important as the load gets further from the wall.

I would recommend the 3" lag screws as that would maximize the holding strength between stud and bolt. If you can increase the bolt diameter, it will have a higher shear strength. Pre-drill the holes so the stud doesn't split.

But that's not where your biggest problem lies. The problem is with gauge of steel around the attachment points of the lag bolts. Thick washers can possibly help distribute that stress along more area of the shelf frame/bracketry. Thicker frame/bracketry will deform less under higher loads. Ultimately depends how they formed the attachment point.
Anything you can do to increase the bearing surface at the attachment point will help.

 

[ItsNemo]

http://www.imagedy.org/pull-out-strength-of-lag-bolts-in-wood/

That might help? I think it says 349lbs per inch...depending on a bunch of factors.

 

[rburke65]

I think you’ll be ok. What all are you storing on the shelf that weighs 200#?

 

[MFolks]

I have in my garage ceiling,two wireframed storage shelving/organizers.screwd into the studs,I bought them at Ace hardware, many years ago they have 4 vertical support points,and are adjustable.

 

[benjamintmiller]

As long as you have nothing running through the wall, like wires or pipes, then you can use 4" lags, but those ones that came with it, pretty much guarantee that you won't penetrate properly installed wires. And, I'm sure they'll work just fine for most folks. That said, GJ ain't most folks, so make sure you miss your pipes n wires n get the real long lags.

By code, a nail plate is required if wires are within 1-1/4" of the stud face. On a standard stud, this allows for a 1" hole to be bored, which means that even the lags shipped with this shelf could hit a wire.

You can probably hold 200# with a few screws... these lags will likely hold thousands of pounds if installed into studs. The shelf looks like the limiting factor here.

 

[matt_i]

The GRK RSS will probably indent the drywall with the bracket behind it if you kept your finger on the trigger long enough. Just saying eventually the drywall at the lower end of the bracket is the weakest link if you use the right screw.

 

[theoldwizard1]

I was thinking of grabbing some longer Spax or GRK RSS in the same diameter, but cannot decide if I would get 2.5" or 3" length.

One of the problems with lag bolts is that if they are too large/long they can crack a 2x4 and you lose a lot of strength. I would use #10/¼" GRK, 3" long.

 

[PoorOwner]

thanks guys,
I ordered a box of GRK 5/16 x 2.5" it is actually a 2 3/8" it will be used for this rack and hanging garage cabinets. I like the no predrill because I don't want to be on the ladder drilling all the pilot holes. I still predrill a small hole and not full depth just so it goes in straight. using a ratchet these screws don't need alot of torque to install, no squeak, no cracking sound, etc.

 

[maxpat82]

One of the problems with lag bolts is that if they are too large/long they can crack a 2x4 and you lose a lot of strength. I would use #10/¼" GRK, 3" long.

you just have to predrill.

It's not an issu in new wood stud....but for sure will crack a dried stud if not predrilled.