Lag screws through 5/8" Sheetrock 3

[CUBUFF]

I have a specification in a project for a ledger to be attached to 2x6 studs on 16" centers to hold a mezanine. The specification states that the drywall is to be removed and the ledger connected directly to the studs using 16p nails.

Could one use long lag bolts (say 5/16" x 6" and attach through the drywall instead?

Thanks,

Jim Marshall

 

[boo1]

No, the drywall will fail in bearing loading.

 

[CUBUFF]

Thanks for your quick response.

If the drywall is removed it seems like the lag bolts would be a better anchor than 16p nails. What size would be appropriate through an 1 1/2" ledger?

Also, could one support a 3/12 glue lam ledger at intervals, attaching with lag bolts to the wall through the drywall? In this way the bearing load would be on posts under the ledger.

Jim

 

[Beggar]

Seems to me that nails are far preferable to lag bolts in terms of part cost and speed of installation.

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[CUBUFF]

Although it would be quicker I think that the lag bolts would be better. It still seems to me that a long lag bolt through the ledger (1 1/2" x 12") and the 5/8" drywall would have bearing capacity since the anchoring would be in the 2 x 6 studs (16" on center). In my case cutting through the 5/8" would cause a large mess and is difficult in the situation.

We had one where we lag bolted a ledger through a 1/2" plywood over a 2x4 wall. I know the drywall is different but it seems that there should be some way to get some bearing. Would it be possible to angle the lag bolts upward into the 2x6 or is there a specialty (eg Simpson) hanger that would accomodate this?

The load on the mezanine is hot excessive using 16" on center 16' TJI 230 joists. With a 100 psf storage loading and 10 psf dead load. The glue lam that the joist attaches to is a 6 3/4 x 18 spanning about 19 ft. If I had to I could put a glue lam against the wall and support it with posts I suppose.

Jim

 

[Beggar]

How is there bearing capacity conferred by the lag bolts?

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[CUBUFF]

I believe that the lag bolts could add enough additional holding power to compensate for the distance of 5/8" and the fact that drywall has no load bearing capability. The compression afforded by the lag bolts and the fact that they would have much more bearing capacity than 16p nails could help.

Angling the bolts upward into the studs could improve load bearing.

In addition I could support the ledger with periodic 2 x 4 posts attached to the wall studs. Thus, anchored horizontally with the lag bolts and supported vertically by essentially cripples, I believe it would hold.

Thanks again,

Jim

 

[Beggar]

Doesn't your specification mandate that the ledger be fastened to the studs? Seems to me that that precludes the option that you're considering.

I guess I don't understand your application because I still don't see how the lag bolts provide any "holding power" that opposes a bearing load being applied to the drywall.

Are you sufficiently confident in your approach to stamp the drawings?

Does your approach conform to UBC requirements?

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[CUBUFF]

You are probably right and it is tempting to just say that the drywall has to be removed for attachments. I believe that the concern was to set up a situation where the mezanine could be easily removed for a future tenant.

The main concern was to make something that would be more easily removable. Puttying holes is easier than a new drywall job. There is still the option of using glue lam beams supported with posts up agains the drywall.

Jim

 

[CUBUFF]

To give you an example of what I am talking about see

http://www.bestdecksite.com/introLedgerPg1.htm.

Jim

 

[CUBUFF]

To give you an example of what I am talking about see

http://www.bestdecksite.com/introLedgerPg1.htm.

See also

http://www.blackanddecker.com/projectcenter/ProjectDetail.aspx?DOC_ID=p_2_102_23914_23934_23983.html

http://www.saradec.com/DeckManual/layoutd.htm

It looks like there might be a lot of bad information out there. The question, "Is there a legitimate way of handling this situation?"
Jim

 

[woodengineer]

Both Simpson and USP manufacture high strength screws: SDS and WS screws respectively. The issue with keeping the drywall in place is placing the fastener in bending. There has been some research done on the diminished capacity for this condition. Contact either of those manufacturers.

 

[CUBUFF]

I found Simpson Strong-Drive information at

http://www.strongtie.com/products/connectors/strong-drive-screw.html

My lbs per lineal foot on the mezanine is 660. Sounds like three rows into 2x6 studs at 16" oc would accomodate this quite well if not the ability to adjust for the bending factor. There was one article at

http://www.fpl.fs.fed.us/documnts/fplrp/fplrp469.pdf#search='lag bolt capacity'

but there was not a lot of particulars.

Jim

 

[CUBUFF]

Common sense would tell me that even given the offset three 1/2" x 5" lag screws into a stud through LSL ledger and 5/8 gyp board would be better than 3 16p nails through the LSL ledger into the same studs. However, I am not finding much to support it.

Jim

 

[woodengineer]

Jim, Contact either Simpson or USP via phone and ask to speak with on of there Professional Engineers. I have found them accomodating and easy to work with. I am sure they have run into this scenario before. Further, Virginia Tech has done some testing of this additional bending as it pertains to bolts for ledgered decks. There is 7/16" OSB sheathing plus (sometimes)drainage washers between the ledger and band/rim board. They developed a reduction factor which accounted for the bending on 1/2" bolts.

Jordan

 

[CUBUFF]

Will do. We have contacted them regarding venting and found them to be helpful as well.

Jim

 

[CUBUFF]

In talking with the engineer he acknowledged that although there is nothing made there is a demand for a fastener that would work with gyp board or sheathing.

The only cantilevered fastener system was their ICF Ledger Connector System made for foam filled concrete walls.

Probably the only options without cutting the drywall would be to bolt the heck out of it and support it periodically with 2x4's lag bolted vertically to the wall. I am pricing also using 3 1/8 x 18 GLB that would have appropriate post placement. Although it is not necessary I would probably lag bolt it to the wall as well.

Jim

 

[vpj]

Jim,

I saw your post and had a couple of questions. In order to get the full NDS design value for a lag bolt, the penetration needs to be 8d, (4" min. for 1/2" diameter bolt), with a minimum pentration of 4d. If your load is 660 plf, a 1/2" lag has an allowable of 220 plf, you would need 4 total at 16" on center. How deep is your ledger? The spacing between bolts may be an issue. Is this a 2 hour rated shaft wall? This is an issue with stair wells that are wood framed. The gyp can't be penetrated and a ledger beam is needed to support the floor framing.

Another option if the situation allows it would be to place a two ply LSL board in the wall framing. The gyp would be able to run past. Provide a double LSL ledger board and connect it to the beam in the wall with thru bolts. The connection would require less bolts. It may work depending on your situation.

 

[CUBUFF]

Thanks for your response. The ledger is 1 1/4" and the depth is variable to around 16". The wall is 1 hour fire rated 2x6 with 1/2" plywood covered by 5/8" exterior fire rated sheating with Hardi Board siding.

I was thinking of using 6" x 1/2" plated lags. A friend suggested I use Simpson SDS structural screws (probably 1/4" x 6").

The wall is already in place.

Jim

 

[CUBUFF]

I should note that the interior wall where the attachment goes is 5/8" type x gypboard. From interior to exterior it has 1/2 gyp, 2x6 Studs, 1/2" plywood sheating, 1/2" gyp exterior sheating, Hardi-Panel 3/8" panel.

Did your calculations on the 1/2 lag at 220 lbs per lineal foot take into effect the 5/8" for the gypboard?

Jim