Repairing roof trusses

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  #1  
Old 05-05-11, 07:02 PM
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Repairing roof trusses

I recently pulled down the ceiling in one room so I can run an exhaust fan duct as well as hang some high hat lights. However, I encountered something that concerns me in the attic.

The house had a new roof put on by the previous owner in 2006 and apparently there were some serious water damage to the roof and structures. In removing the ceiling sheet rock I was able to see how the repair was done and it concerned me.

There are three trusses that were damaged, to varying degrees.

First, let me show a sketch of the structure. The exterior wall is of 12" concrete block. On the top is a solid concrete tie beam, with hurricane straps to the roof trusses (Location of property is Miami, Florida). The rafters extends at an angle five feet beyond the wall, creating an large overhang. A piece of 2x6 on the outside attached to the concrete wall using metal hangers, then wood panel (T-111) nailed to the underside forms the soffit.



The area in red along the top of the rafters were damaged by water and basically rotted away. The previous roofing repair was done by sistering another piece of 2x6 alongside the rotted rafter. But in looking closer, the sister 2x6 was NOT nailed to the bad rafter at all, instead it was secured by nailing the roofing plywood from the top to it. Secondly, this piece of 2x6 is short. Since the overhang is 5 feet, the piece of 2x6 is 8', it extends all the way to the edge of the overhang, then 12" of it over the block wall, meaning only 24" of it is inside of the wall. Seems too short?

Here are some pictures on two of the trusses.

This one was left "as is" without repairing, but there were damages on the top side of the 2x6 as well as more damages in the soffit area.



This one you can see it is very badly damaged. The piece sistering it behind couldn't even nail to it because it was so badly damaged.



A view of the roof trusses in the attic, away from the damaged edge.



Is the repair adequate?

Is there a way to do it better? By sistering another piece on the other side, holding the bad piece like a sandwich?

Should I make the piece longer?

Or should I just leave it and create a new piece in between two bad pieces, glue it to the roof plywood?

Comments and advice appreciated.
 
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  #2  
Old 05-05-11, 07:45 PM
Join Date: Dec 2007
Location: Chicago
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If you can ID the truss manufacturer, they may be willing to design the required repairs. If not, they have to be designed by a qualified design professional (architect or engineer).

That said, I see many such repairs to damaged truss ends here in Chicago due to moisture intrusion at parapet and/or split faced block. And yes... the repair is basically plywood nailed to both sides of the truss, the important details specified are the portion of the truss to reinforce and the fastener schedule.
 
  #3  
Old 05-06-11, 04:01 AM
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Are you sure it's not nailed to the truss? I would think it has to be nailed somewhere. It would be harder to not nail it to the truss and only to the plywood.
 
  #4  
Old 05-06-11, 09:27 AM
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Originally Posted by drooplug View Post
Are you sure it's not nailed to the truss? I would think it has to be nailed somewhere. It would be harder to not nail it to the truss and only to the plywood.
They used very long nails, 3", so it is very easy to see where they nailed it on the other side. There were only two nails that came out.

One was nailing through the rotted wood. That nail was totally useless when I put my finger on the sharp end where it protruded, the old wood just sort of disintegrated.

The other nail was done into the "good part" of the wood further back. One nail, for some reason they nailed it too low and it basically pierced through the bottom 1/4" of the old wood.

Other than these two nails, I didn't see any. However the wood is secured, from the top. I know it's strange. I could be missing something, but I don't think so.
 
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