Hacked up joist needs sistering,HELP!


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Old 06-15-12, 07:03 PM
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Hacked up joist needs sistering,HELP!

I am in need of repairing an outside deck that has living space below.

Here is the problem. The 2X10 joists are 14' long and one end of 4 of the joists are rotted about 3" from the end. I plan on cutting the bad ends off and sistering. The other end of the joists have been cut down about 3 1/2" to fit adjacent to the 2X8 joists above the studwall. My thinking tells me that I really only have 2X8 joists structurally but I need the 2X10 height to keep the deck where it needs to be.

Can I sister the entire 14' with 2X8 and build up the end that needs to be 2X10??

Could I just sister the 2X10 halfway(7')

Should I just replace the entire joists including notching them to fit the 2X8 end?

Any help is much apprediated.

Thanks,
Dan
 
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Old 06-16-12, 07:06 PM
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Install new joists about 3 inches to one side of the damaged joists, then cut out the damaged joists completely. Use 2x10s & cut them exactly how the others were cut to meet the other wall. After the damaged joists are removed, add more joists if needed for support. They won't be 16" on center but it won't matter.
 
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Old 06-18-12, 10:24 AM
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Can't I just sister new 2X10's halfway from the rotted end? Getting complete new joists in there is not possible.

Thanks,
Dan
 
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Old 06-18-12, 10:27 AM
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How do you have access to glue and screw sisters halfway but cannot put in new joists?

Can you post a couple pictures?
http://www.doityourself.com/forum/el...-pictures.html
 
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Old 06-18-12, 08:06 PM
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If you sister a joist against rotted wood, the rot will spread to the new joist. You can get a new joist in there even if you have to remove others first. Cut the joist to size. Insert it on it's side & on an angle so it reaches both plates, then flip it on edge.
 
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Old 06-20-12, 10:57 AM
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Lots of things in the way, including heating ducts and the intake for the heat(hot air)uses the joists as part of the ducting.
 
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Old 06-20-12, 11:00 AM
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I don't know about this but, as Pulpo said, you at least have to get rid of all of the rotted wood.
 
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Old 06-20-12, 11:04 AM
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I wasn't planning on leaving any rotted wood. I would just cut off the 6" that is rotted then sister each side of the 2X10 halfway across.
 
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Old 06-21-12, 05:24 AM
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If you are going to do that, at least add a post & a footing where the new piece of joist & the old joist meet. That will give you the same structure as if it were all one.
 
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Old 06-22-12, 04:44 PM
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Yes, cut out the rot, it's not as catchy as it sounds, LOL: UMass Amherst: Building and Construction Technology Wood Myths: Facts and Fictions About Wood

"with living space below" may be difficult to add a post........ just one sister 1/2 of span if the rot is within 12" of bearing. Add 1/2" through-bolts- 6" from each end and one in the middle, nailing the length of each at 16"on center with 16d nails, staggered 2" from top and bottom: per fig. 1, here; http://www.finehomebuilding.com/PDF/Free/021184090.pdf- run this repair by your local AHJ.

2x8 are over-spanned for a deck with ceiling below at 16" on center, Table 2: http://www.awc.org/Publications/DCA/DCA6/DCA6-09.pdf

At 483# each bolt, 7' span x 40# x 1.333' (if 16"o.c.) = 372# at bearing, fully loaded, again- check this with your inspector. Connection Calculator

If the rot is on the bottom 3" by the width of the bearing plate below, you are allowed a notch 1-3/4" high by the plate width (may change because of the rip); Fig. 2: Troubleshooting Guide to Residential Construction - Google Books

Did you read Fig. 3? Your repair is in the outer 1/3 of the total span, leave any wood that is not rotten, treat the cut end with copper based preservative if any is left.

Gary
 
 

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