I am not sure whether this topic belongs to Capentry, Construction or Roofing. So if I posted this to the wrong forum, my apologies.
Some background. The area of repair had a roof leak, and previous owner let it sit and rot. I discovered the problem when I had to rework some electrical conduits in the attic, so I removed some ceiling sheet rock and found that the heel of one truss has COMPLETELY disintegrated - meaning I can break pieces of the wood off with my bare hand. Here is a simple illustration. The dashed line section were rotted away.
The good news is, it appears to have been in this condition since 2004, and the roof has not sagged. This is probably the next truss 24" over is a double truss, as you can see from the picture below.
I took a recipricating saw and cut back to where I have solid wood, then I supported the joist with a double 2x4, for now.
My first thought was to put in new 2x4s to replace the missing sections, then use plywood gussets on both sides. However, with both the rafter and joist missing a short piece, this may not be good enough. I also felt I am not going to be able to make a large gusset because of all the pipes that runs through there. I decided to sandwich
the original rafter and joist on both sides with new 2x4s.
First, I nailed a sheet metal plate from the back side to the original joist. Then I put a 10 feet piece of 2x4 behind it. Nailing the other half of the metal plate to the new 2x4. Then I did the same to the rafter and attached a new 2x4 behind it. I nailed the old and new wood together with 3" 10d nails spaced every 10" or so. This is depicted below. The original 2x4 is of darker color
, the piece behind it is the new sister 2x4.
Next, instead of putting in new 2x4s to connect to the original wood members, I cut two sheets of 3/4" marine grade plywood to the shape as shown below. I am thinking this gives me a rigid joint at the heel.
The two sheets of 3/4" plywood results in the same thickness as a 2x, and it is one piece. I plan to glue the plywood to the new 2x4 behind it, then nail it together with 3" 10d nails, as shown below.
Then I plan to put in another 2x4 joist and rafter to the front of it, nail them in place, then drill 3/8" holes through all three wood members every 24", and use 3/8" bolts with large washers and nuts tightened from both ends. The plywood sections would be in the middle when I am all done. With so many conduits in the way, I can't think of another way.
Would appreciate any comments on the approach and what I could do better.