ideas for strengthening structural mistakes

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Old 03-19-19, 10:20 AM
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ideas for strengthening structural mistakes

My wife and I purchased a house with a detached 3-bay garage. On the back side of the garage the previous owners hacked in a 16x30 ft lean-to. The joists are 2x6x16 treated and set on Simpson joist hangers on both ends on 16" centers. The one good thing they did was use 6x6 posts and spanned no more than 10' the long way and 8' the short way, so if you imagine looking at it from the front, there are four posts 10' apart on the outside, and other 4 posts 8' behind those, and nothing under the ledger board attached to the garage. The top ledger board from what I can tell is screwed into the studs framing the garage.

This whole thing was put up with regular deck screws, no nails. None. All the joist hangers are up with regular 3" deck screws. This was pointed out during the home inspection and the inspector said he felt like the structure was stable and safe but that it could be strengthened to make it safer. As of right now, this structure shows absolutely no sign of failure. My best guess is that it's around 5 years old. There is no sagging, all the joists are securely fastened. The roof is shingled and I got up there and bounced around and it feels solid. Obviously I'm concerned about the longer term implications of the structure because I do keep my mowers, trailer, and other equipment under it. I'd also like to use one of the 10' sections for a dog kennel one day.

I cannot afford to take down this structure and do it correctly right now, we just sunk everything into the house. I would like some ideas for strengthening the structure so I can use it long term - if possible. One idea I had was to replace the deck screws in the joist hangers, one at a time, with Simpson structural screws approved for joist hangers. My concern there is that the replacement screws might not get enough "bite" since a hole is already there from the existing screw, and I was also afraid a nail would be ineffective in that case as well. I am also planning to put some posts in right next to the garage wall to support the attached ledger board at the highest point of the structure, and then run some members long way bolted to the posts to support the underside of the joists on both ends and in the middle.

Any ideas or suggestions here would be greatly appreciated.
 
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Old 03-19-19, 12:45 PM
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Nails are specified for use with joist hangers but I think it's largely because that is what the manufacturer specified. When I built my house I discussed this with my inspectors. They thought good quality screws could be better than nails but at that time nobody had studied screws or written them into the code. So, the only approved fastening method was with nails.

Here is the first article I found that covers the difference between nails and screws. I don't think their comparison of #6 and #8 screws to 16d nails is fair and seems a bit apples and oranges to me. I most commonly use #10 which are getting closer in size to a 16d nail.
 
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Old 03-19-19, 01:39 PM
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Thanks for your reply. Simpson now certifies some structural screws with some (if not all) of their joist hangers. I am not sure yet without actually checking with them what would be recommended for the hangers I have. I removed two of the screws to see what I had, and they look to be #9 3" power pro screws (gold-looking) which I've used on deck boards before. They appear to be coated for treated wood because they show no signs of deterioration. I have no doubt they hold, the lean-to is incredibly solid. I think the real threat I've read about is the shear strength of the screw head and shoulder, not the size (diameter) of the screw compared to a 16d nail. I might be over thinking all this but when I saw all those screws in the joist hangers I immediately started to think of ways to correct something I perceive to be wrong.
 
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Old 03-19-19, 04:07 PM
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All the joist hangers are up with regular 3" deck screws.
So just to clarify, from your description it sounds like there is no concern that any short cuts were taken with the structure and that your only concern is that deck screws were used instead of nails in all the hangers?
 
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Old 03-19-19, 05:09 PM
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Those screws are surprisingly strong. I would be more concerned with the head shearing off.
Why not replace them with 3" #10 stainless screws ?
 
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Old 03-19-19, 05:32 PM
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If you're going to use screws, the screws need to be rated structural joist hanger screws in order to be used with any structural hanger... such as Simpson SD9 or SD10 Strong-drive. There is no concern about the old screw hole since the existing screws are much smaller.

A ledger does not need to be supported with posts, provided it has been lagged into the studs every 16" with the correct fastener... such as 4" ledgerlocks and provided those fasteners are 2" from the top and bottom edges.

Can't give much more advice without a photo, and you didn't tell us anything about the beam sizing.
 
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Old 03-20-19, 05:47 AM
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Sorry I do not have the pics with me today, but first I'd like to thank all of you for your responses, and I'll address some of the questions and comments from above.

So just to clarify, from your description it sounds like there is no concern that any short cuts were taken with the structure and that your only concern is that deck screws were used instead of nails in all the hangers?
The deck screws in the hangers is one concern.

A ledger does not need to be supported with posts, provided it has been lagged into the studs every 16" with the correct fastener... such as 4" ledgerlocks and provided those fasteners are 2" from the top and bottom edges.
The bigger issue is that the same 3" screws are attaching the ledger board (2x6) to the garage. There are no lag bolts anywhere on the 30' garage wall. They did use lag bolts to connect the rims and joists at the posts. Now they did use 3 screws into each of the garage studs, but with the sheathing in between the ledger board and the stud there can't be more than an inch of the screw into the studs.

The garage is unfinished so while I would have to move a crap ton of stuff, I do have access to the framing members in the garage. One idea I've gotten, instead of posts outside, is to nail in 2x8s between every other stud inside the garage, and then lag bolt the ledger in those spots. While time consuming, that would be relatively easy to accomplish and would certainly strengthen the connection point. I think if I did at least that I'd feel a lot better about it.
 
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Old 03-20-19, 06:15 AM
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You just need to remove the deck screws in the ledger and lag it with 4" ledgerloks. I don't know why you want to complicate this.
 
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Old 03-20-19, 06:44 AM
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I think it's less about me wanting to complicate and more about having a hard time describing how they built it. I don't have access to most of the deck screws attaching the ledger because the joists and hangers are covering most of the connection points. Basically the joist spacing on the lean-to aligns with the garage studs. So the only way I'd have anything to bolt to would be to put something between the studs. Does that make sense?

I should add here that I'm "assuming" they used the same deck screws even though I cannot tell specifically because of the joist placement. There are several points between a couple of the joists like over windows where I can see three deck screws going into a window header, so my assumption is that's the way it is all the way across. I "can" lag bolt at these locations, but that's only about three locations across the entire 30' span.
 
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