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Truss Repair

Truss Repair

Truss Repair

(OP)
I have a 30 X 50 wood frame shop that I am upgrading for better hurricane resistance. (in west central FL).  The shop has a 16 ft wide garage door that will be replaced with new 140MPH door.  The old door had an opener(now removed).  When the opener was installed (before I owned the shop) the 3 trusses inboard of the door were notched to clear the opener rail.  The notches are .5" high x 3.5" wide on the bottom side of the truss.  Approximately 2' from these notches is the center of the truss the bottom of which is made of two spliced 2x8s 15 ft long (~30 ft span).  There are two of these "2x8" trusses and the rest of the shop trusses are all 2x4 members except for the 2x6 tops.
The gable wall over the 16' door is bowed out 1.5" at the top of the double 2x12 header.
I plan to splice a 2x6 onto each of the notched 2x8s going 3 ft, or so, past the center and the notch.  Should I jack the truss up to level before splicing?  (now - about an inch sag at the center).   
I also plan to pull the gable wall into plumb as follows:
1) stuffen first three trusses laterally (like gable braces but not connected to the gable wall until the gable wall is pulled in.
2) already added third 2x12 header
3)already added vertical 2x6 face boards for new door mounting over four existing 2x4 studs at side supports of 16 ft door opening.
4) temporary install 8'long - 4x6 to bottom of first three trusses touching new (plumb) 2x12 header above door.
5) drill through outside wall above door to meet 4x6 and screw in qty 2- 3/4" x 10" long lag screws into end of 4x6 pulling wall to plumb (hopefully).  2 1/2" holes will predrilled in the end of the 4x6 for the 3/4" threads (using 90% of root dia of lag screw due to thread going in parrallel to grain).  There will be a 3'long 3"x3"x.25" steel angle between the bolt heads and the exterior wood sheathing.  Also going to add some 1/2" plywood to the  trusses (laterally accross top of bottom cord) to help trusses re-sist bowing towards the door during wall pull in.

Any thoughts, additions, changes, or improvements to the plan.

Just replace roof with 30 year shingles w/ special nailing, edges glued, and sheathing re-nailed 3" on center (all over)
Overhangs cut back from 36" to 18".
Load path hurricane straps/clips/connectors will be added in Feb. along with added foundation anchors.

Thanks
Stan Light

RE: Truss Repair

I'd be concerned about the horizontal force you will place on the truss bottom chord. Tying them together isn't really going to do much except share the load. I'm not sure what is meant by "like gable braces". They don't have much capacity to resist lateral horizontal force perpendicular so, even though the load will be 1/3 (if you tie 3 trusses together) it still seems problematic. You would have to add in some kind of diaphram across the full width of the building with suitable chords and anchorage at each sidewall or maybe engage substantially more than 3 trusses with bracing.
I'd want to understand why the endwall is out of plumb before I just tried to pull it back into plumb.
Also, I think you are saying you will fasten into the end grain of the 4x6 with a screw. I don't think there is any allowable capacity for withdrawl of screws in endgrain.

Just some thoughts. (you asked for those too)

RE: Truss Repair

(OP)
Yes, I know that there is no really good way to pull this gable wall in but short of a 'sky hook' there is nothing to push or pull from.  There was a floor put in the truss area (plywood -1/2") that is 8' wide and the full length of the 50' shop except for the 2 trusses at the front door and the one truss next to the gable wall at the back door (16' doors both ends). The 10 sheets of the 'floor' are fairly well nailed in
I plan to tie in the last front truss to this 'flooring system' using plywood and be pulling against the better part of 24 trusses.  The wall has been this way at least 21 years as I have been here 20 and we were told the door opener was year old when install. The opener top rail was firmly mounted to the 16' door header that is out of plumb. So the wall didn't move slowly as it would have pulled the small screws out holding the opener up.   
Another note - I will have a support at the bottom of the header (which is plumb) to keep the whole wall from pulling in, so I am really rotating the header at the top and the gable wall at the bottom.
With 21 years of being this way there will probably be more stress built up in un-warping the boards than is building stresses.   
The maim beam I am pulling on is a 4x6 (tied into the first three trusses).  Into the end of this beam will go the two 3/4" lag screws.  The wood structure design data I have says parallel to the grain screws need 9 thread root diameters of thread for proper engagement and strength. On a 3/4" screw this would be 5.04" (.56 root dia x 9) but I will only have only 4.7".  I am using two of these screws and based on allowable tensile loading I am either going to move this gable wall and header and inch into plumb or move 20,000 pounds of roof and inch out of plumb. There is also the possibility stripping the threads in the wood (get longer screws) or run out of air impact driver power.
I believe the problem is warped double 2x12 header beams. The gable wall is only out of plumb at the center of the 16'door and there is no noticeable vertical sag in the header boards - they are just bowed out and inch at the top were thay attach to the gable wall bottom.

I don't want to install my new 140 mph garage door on an out of plumb wall.

Thanks for your thoughts - will try to incorporate your concerns into the 'PLAN'

Thanks

RE: Truss Repair

You have not indicated specifically whether or not you are installing screws into the end grain. My apologies if you understand this distinction but I am not sure from your syntax. When you say "into the end of this beam" I think you are saying the screws will be loaded in withdrawl. That is not the same as parallel to the grain. Parallel to the grain refers to the direction of the shear force (versus perpendicular to grain) not a withdrawl force (although I realize the literally "withdrawl into the end" is parallel to the grain).   

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