How to fix improperly installed joist hanger?


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Old 02-07-17, 08:12 AM
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How to fix improperly installed joist hanger?

I hired a home inspector to inspect my brand new house, and the most serious problem he found is the improperly installed joist hanger around the cantilever beams which supports the fireplace. As per spec, the gap between the two joist are no bigger than 1/8 inch, but it's more than 1/2 inch in my house. I will request the builder to fix it, but if it's a no go, could it be fixed by myself? and, how serious the problem is? could be safety issue? If it's a safety issue, I think I might involve city inspector into the case.

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Old 02-07-17, 08:16 AM
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Post a picture of this beam from farther away, please. We will want to see the front and back of the beam as well as the front of the joist hanger.

I'm guessing your problem is similar to that described in Figure one, follow this link.

http://www.woodbywy.com/2016/10/03/w...onsiderations/
 
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Old 02-07-17, 08:54 AM
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I don't have more pictures with me right now, but I think you are right, the problem looks very similar to the figure one. Will adding a L bracket under every connection secure the structure? Thanks.
 
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Old 02-07-17, 09:36 AM
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No.

Here is a quote from the Simpson catalog:

Eccentrically-Loaded I-Joists
Supporting a top flange hanger may
require bottom flange restraining straps,
blocking or directly-applied ceiling
systems to prevent rotation at the
hanger location.


3 methods are mentioned which can prevent the beam from rotating. Generally, I see blocking used most often in the framing stages of a home.

If you want to use a restraining strap, you need to use an approved and rated strap... not just a "bracket". A structural engineer or a building inspector could better advise you on what to use, but it would need to be something like a length of Simpson CS22. For example, an engineer might be able to calculate that a 24" piece of CS22, when bent to form a 90 degree strap and fastened (as Simpson specifies) to the bottom of the joist and the back side of the beam backing, would have enough strength to resist the tension created on the beam by the Eccentrically-Loaded loaded i-joists.

An engineer would tell you how long of a strap to use, and how many of them are needed. Its why your inspector refers you to a "qualified engineer." They know the maths, or at least can figure it out and assume the liability.

Obviously we can't see or understand the problem without being there. If this is a minor problem with very small loads, your builder can probably strap it together no problem. He would need to force the rotated beam back together with blocking, then strap it to prevent it from rotating again when the blocking is removed.
 
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Old 02-07-17, 08:19 PM
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So basically this is the section has the problem, around the cantilever beams which supports the fireplace.

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Old 02-07-17, 08:54 PM
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Before you get carried away you might ensure that there really is a rolling to the side deflection going on... (ensure the joists werent cut that way intentionally! The builder might have done that to eliminate rubbing or squeeking.)... you can check the sides of the carrying i-joist for plumb, check the bottom chord along its entire length to see if it is straight or if it is rolling away with a string line or laser.

If they are rolling away, install flat 2x4 blocking inline with the set of 3 joist hangers pictured... put the blocking between the bottom chords of the center pair (of 4 joists) first, then install blocking between the outer pairs which will force the i joists over tightly (within 1/8").

As for the 4 joists, it appears too tight to bend a tension strap in the space available... so if a tension strap is used, you would need to add solid blocking to build out both sides of that 3rd i-joist that is next to the ductwork... put flat 2x4 blocking in that narrow space between joists... and then wrap your tension tie across everything and up the outside of that 3rd joist that is next to the ductwork.

But like I said, I often see flat bottom chord blocking used to accomplish this same thing. You could put flat blocking between the joists that are way off to the right of the picture (top pic) and force that carrying i-joist over. (Assuming you start on the far right side of the room and block back toward the area with hangers on the far left).
 
 

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