Building chimney crickets, and the like.

[mannyrock]

Dear Guys,
 
   If you have read my previous posts, you know that I have had to reframe the roof structure around my chimney, because the idiots who originally built it left all of the short-cut rafters leaning directly against the masonry itself, not attached to a header or anything else.     My research indicates, over and over, that you cannot have any wood from the framing touch the chimney, and that a minimum gap of two inches is required between the framing and the chimney.
 
    OK, I've done all of that, and I am now going to have the shingles all taken off the roof and new decking put down.  After this is done, I will need a very large cricket built behind my chimney, because the slope of the roof runs right down against it.   It will be a complicated cricket, because I can't direct the water to flow around both sides of the chimney, only one side.  This is because my house has an upper roof, and a lower roof.  The chimney comes up through the lower roof, and one side of the chimney is flush up against the wall of the taller section of the house.
 
  Here's my problem.   I am getting ready to design/ build the cricket, and have looked at lots of videos and plans online about it.  And each and every danged one of them show the carpenter nailing one end of the struture 2x4s down on the existing roof deck, and the other end right up on and against  the chimney itself.  Not only does the lumber touch the chimney, it is beind nailed or bolted directly to it.
 
   So what gives here?  If it's illegal to have the lumber touch the chimney, then it's illegal to have the lumber touch the chimney.  There is no "cricket" exception.   How are these guys just doing this, calling it "good" and getting away with it?  What is really suppose to be done?
 
Thanks for all advice. 
 
Mannyrock
 
 
 
 
 
 
 
 
 
   
 
 
 
 
   OK
 
 

[FPH]

I would suspect that the chimney already is required to have a double insulated flue and that you would be attaching the cricket to a framed box surrounding the actual flue.  I'll see what I can look up in my inspection books.

[FPH]

You would be required to have a 2" gap between the flue and the framed box.

[mannyrock]

 
   Thanks for the replies FPH.
 
   I'm not sure what you mean when you say the flue is in a framed box with a two inch gap.
 
   Best I can tell, my chimney consists of a cinderblock tower, with a terra cota flue cemented inside, and a single layer of red brick on the outside.   I don't think there is any gap or spacing inside this structure.
 
   All of the online pictures show the carpenters nailing the 2x4s directly to the red bricks on the back of the chimney.  They are leaving no gap for either fire protection or chimney sway.
 
    I would think the proper way to build a cricket would be to create a free standing triangular wood structure, that can stand by itself on the roof, and then nail it down on the decking two inches away from the chimney.  The gap would then have to be flashed just like the regular framing gap in the roof.  Is this correct?
 
  Thanks,   Mannyrock

[FPH]

Is there space between the cinder blk and the red brick flue?

[mannyrock]

    Thanks for the question.
 
    When I am on top of the roof looking at the chimney, the entire top of the chimney is crowned with cement, leaving only the terra cota tile flues stick up through it.   
 
   When I stick my head up inside the fireplace a look up, all I see is cement (stucco like) going up the chimney, and then the tile flue.    No gaps anywhere.
 
   This house was built 32 years ago.   On most of the houses I see built around here, they start by building a cinderblock chimney, leaving little metal tags hanging out of the seams between the blocks.  These tags are fairly short.  I assume that they then just build a red brick exterior, going straight up all around the block, secured with the metal tags.   I never thought about whether there was a gap being left between the block and the brick coating.  Hard to believe since the chimneys are so tall.    No way to tell whether there is one currently between m tile flu and the inside walls of the cinderblock flue.
 
   So, I guess I'm not sure what I've got.    Maybe the best thing would be for me to make the triangular, pyramid structure so that it can "stand alone", and then just nail it to the roof decking, leaving the gap between it and the chimney.   I'm just really surprised to see all of the internet instructions, telling you to nail it to the brick.
 
   Besides fire hazards, chimneys settle and sway in the wind.  I can tell for sure that mine has leaned one inch off center towards the back of my house.    It pushed against the short-cut rafter that was jammed against it, and caused that rafter to bend in a downward bow, about 3/4 inch off its original true line.   As a result, there is a dip in my roof decking, along that whole rafter, all of the way down the roof. 
 
   This bend in the rafter is now permanent, as it has dried as hard as iron.  There is an angular web chord, built into the truss, which supports a portion of the underside of this bent rafter, and it has bowed 3/4 off center as well.      I think the only thing I can do is have them pull the decking off of the rafter, and glue a long set of shims on top of the rafter, to level out this dip in the rafter, before they putt new decking down.    I will pre-cut several 8 foot sections of yellow pine shims, ranging from 1/4 inch, to 1/2 inch, to 3/4 inch thick, so that hopefully they can level out the rafter.     I use my table saw and rip these shims by cutting yellow pine 2x4s.
 
   Any other advice would be appreciated.
 
Thanks,
 
Mannyrock   
 
   

[FPH]

You could also forget the shims and just scab on a 2x6 or 2x8 to your rafter and make the scab straight.

[FPH]

Your contractor should have gotten a permit if he completely reroofed the house.  If you really want to CYA( with your Insurance Co.) I'd call the Fire Marshal out to inspect your chimney. Better safe than sorry.  Here, they would be happy to inspect it.

[mannyrock]

 
  Well, I don't have enough money for the contractor to totally re-roof the house.  He is going to just replace up to 10 sheets of warped, water damaged plywood decking before he puts the new shingles on.
 
  Thanks for the advice.
 
Mannyrock