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make a truss for contractor roof screw up snow load

make a truss for contractor roof screw up snow load

make a truss for contractor roof screw up snow load

(OP)
snow load made contractor stick frame roof no good - rafters way overspanned.  147#/lf D+L+S applied to each 4:12 rafter (24" on center), 24' span, 2x6 rafter, 2x8 cieling joists.  trying to come up with a good makeshift truss fix, tension loads a bit large for joist to rafter connection. here is what i have come up with.  perhaps a manufactured plate would be better then simpson strap... any comments appreciated, i prefer to get at the project first and send it on off to the truss manufactures  rather than trying to fix after the fact. attached is a quick  ACAD file.     

RE: make a truss for contractor roof screw up snow load

Check the end distance of the bottom chord fasteners at the heel. Is the vertical web member notched to fit around the ridge board? It looks like a lot of nails there, which may cause the end of the web and/or top chord to split.  Not sure I understand the diagonal web location; it appears to be butting in to the narrow face of the top chord but at the side of the bottom chord.  (Are the top and bottom chords in the same plane?)

RE: make a truss for contractor roof screw up snow load

It looks as though the simpson strap connectors are too close to the edge of the rafter/joist interface.  Sistering on an additional joist that bears on the walls and fastens to the rafters would reduce the tensile stress situation in the joists.  Adding two angled web members between the rafter (where you have it) and at 1/3 the span of the existing joist, then up to the top of the kingpost - using nail-on truss plate - would simulate a fink truss (W shaped-web configuration with a king post).  This would also get rid of all the nails and splitting possibility at the center of the existing bottom chord.  This suggested solution might be considered overkill, but it may work for you.

RE: make a truss for contractor roof screw up snow load

Sounds like purlin bracing to interior wall or beam would be better and forget trying to make trusses.

RE: make a truss for contractor roof screw up snow load

(OP)
the room is 24 ft x 24 ft and 8 foot cieling so a beam solution is not the best.  there are no interior walls.  

what may not be entirely clear from the crummy detial is that the two members - rafter and joist are not in the same plane (typical stick frame construction) so... the proposed new diagonal web butts into the rafter but nails into the joist.  and yes the idea was to notch the vertical member into the ridge board (and butt against the joists - but use screws at that connection H9 simpson)could use a 2x8 to better handle the nails for all the new truss members...

yes, the straps are certainly need to be looked at, but i was planning to add a sister joist just to make the sides flush for the ps218 straps.

i realize there are spacing issues and edge distance issues all over the place at every connection... but the other choice is to throw in a steel beam (probably 30#/ft weight) or several wood beams and still have to kick up to support the rafters which seems like just as much work - you have to follow the new load path - and you have ugly beams at 7' high.  

RE: make a truss for contractor roof screw up snow load

Maybe too much work for the contractor, but a lot less work for you.

RE: make a truss for contractor roof screw up snow load

(OP)
decided to go with a plywood gusset 6 feet long at each end of every "truss" instead of the straps.  

RE: make a truss for contractor roof screw up snow load

6 foot long plywood sounds like it might result in a "waste" of the last 2 feet. Would 8 foot pieces be better?
Also, is the ceiling joist one piece or is it lapped (which seems more likely)? Since all the pieces don't align, I wonder how much blocking will be needed.

Would it be possible to install a 14 or 16 inch deep I joist along side of each truss instead? Bearing length might be tough but I'm wondering about all the nailing and blocking (labor cost).

I suppose it's not polite to ask but... how did the roof get built without someone (owner, engineer, building official) noticing the lack of roof structure?

RE: make a truss for contractor roof screw up snow load

(OP)
the ceiling joists are full length which is good!  i am glad i dont have to deal with download issues on the overlapping ceiling joists.  

and you are right, 8 foot would make just as much sense.  and i dont think there is any room for beam, and if there was you would have to kick up to midpoint to each rafter anyway = as much labor as truss??  

update - they are running into more issues because of no permit - like zoning!!!  heh heh.... the house was built without permit, so the contractor just built his "standard" roof stick framing that has "worked and never failed for 30+ years.... etc.. etc...", but he failed to realize that the load was effectively doubled because of snow...

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