Cantilever kitchen addition question

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  #1  
Old 05-25-10, 07:49 PM
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Cantilever kitchen addition question

I am adding on a cantilever onto my kitchen. My original plan was to go out 2' and it is about 10' wide. My city is requiring me to have an engineer sign off on it before they issue a permit, so I met with one today. He pulled out the TJI manual (mine are 12" joists with 12" spacing) and found the cantilever section. It says as long as I go back at least 1.5 times the extension I can go up to 4'. This means if I was conservative at 2 times I would add in a 12' 2x12 (8' in and 4' out). Even though the manual says it will work I want to get some feedback. As an FYI there will be very little weight on this extension other than tile and a table.

Thoughts?

Thanks,
Justin
 
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  #2  
Old 05-26-10, 03:14 AM
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Welcome to the forums! Usually 1 1/2 times is good enough for a small cantilever. Moving it to 2 times is better. Are you planning on making it 4' now? Has the engineer signed off on that as well? Not sure how the engineer will suggest they be fastened, but I like to place dimension lumber between the web on the inside and bolt them to the sister adjoining them. But go with the engineer's recommendation to keep everyone happy. Good luck with the addition.
 
  #3  
Old 05-26-10, 07:27 AM
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Thanks for the welcome, I think I'll really like this site. My wife would love if it was 4' and the engineer said it would work, but I don't want to pay for it down the line in repairs. Have you ever done a 4' cantilever? The engineer does want me placing osb in the web. The tji manual says to place two rows of nails 6" apart along when attaching the joist. I am also going to use adhesive liberally in both the osb and the new joist. I think I would feel more comfortable bolting it. What size bolt do you use and how far apart do you place them?

Like I said, I know the manual says 4', I just would like to hear if that will work in real life without any issues before I pursue.

Thanks for your help,
Justin
 
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Old 05-26-10, 03:45 PM
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4' cantilevers are common and should pose no problem if you follow the engineer's and TJI's recommendations. I have done longer ones, but the tails are so far back in the structure it almost made it not worth doing. One fear, and I have run across it in repairing bad ones, is too short of tails. Running through the kitchen and the weight of the cantilever popped all the tiles and raised the flooring nearly 1/2".
 
  #5  
Old 05-26-10, 11:22 PM
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That makes me feel a lot better. I think I will do the full 4'. I always like to get real life input before I embark. I will feel better with the bolts (at least a few every few feet along with nails). One last question for you - the tji manual gives a picture, but doesn't give great written instructions. It looks like the picture is a solid 2x12 versus another tji. How do you normally do your cantilevers? TJI or solid?

Thanks again
 
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Old 05-28-10, 02:39 PM
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TJI, but I tend to overkill, by adding additional material in the webbing the full length to help with bolting, etc. They are probably showing adding a 2x12 in the webbing for bolting, not sure.
 
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