i think i'm screwed wall thimble too close to floor joists above

[jeepin in maine]

the house i recently bought(bank foreclosure) has an outside masonry chimney with a clay liner for the basement stove.1st block is filled solid with mortar,second block has my clean out,and the 3rd block is where my wall thimble enters.i was just going over the install instructions for my quad 4300 and it says [the location of the opening thru the wall to the chimney must leave a minimum of 18" vertical clearance between connector pipe and ceiling to prevent ceiling from catching fire when using single wall pipe].............i've only got 8" from top of pipe to bottom of floor joists(joists are covered by durarock with 1" spacer between durarock and joist.am i screwed?any way around this?if i were to have the wall thimble moved down 10" it would then be trying to enter the chimney thru the bottom brick thats filled solid.
between buying the QUAD 4300,6 cord of wood,and having the chimney serviced i've spent my whole winters fuel budget and now i'm afraid that its unsafe.HELP!

 

[jeepin in maine]

also i have an old lakewood smoke dragon in use on this chimney at the present time...advice?

 

[swestall]

Use double wall pipe, check code with a certified installer in your area: but I think that will do it.

 

[webbie]

A pipe heat shield may also do the job - but I think only to 9", so the double wall deal may be the best way to go. This means double wall INTERIOR pipe, much less $$ than the double wall insulated chimney stuff.

 

[jeepin in maine]

so use double wall interior pipe from the stove to the wall thimble?will i still have an issue where the thimble passes thru the concrete wall(since the sill sits directly above it)?

 

[jeepin in maine]

i just spoke with a local stove shop. he says the double wall pipe will fly,but that i still have an issue of not having 12" of concrete above the thimble.i've got about 8".any ideas?

 

[webbie]

Yes, I just thought of that issue! You didn't ask about it, so we didn't answer.......

There are probably multiple ways to address this, but I have to check my NFPA.

Some companies make wall thimbles that can reduce this, but that would entail some concrete busting (as would any real solution).
(broken link removed to http://hartshearth.com/productcart/pc/viewPrd.asp?idcategory=40&idproduct=4033)

If the wall thimble is large (8"), you might get away with installing a piece of insulated piping in there. Let me browse the NFPA stuff an get back to you with some more suggestions.

 

[webbie]

OK, as usual, codes have changed in this matter. Of course, that does not mean that the tens of millions of chimney installed to the 2003 NFPA and before are going to burn houses down, but here is the CURRENT (2006) NFPA stuff...attached.

Note, it used to be that 9" of solid masonry was required around a crock - so this may be the standard yours was installed to. Current (as enclosed) calls for 12" of solid masonry or the other ways.....

Of course, you are not (as addressed by the code) passing though a combustible wall per se. But I think the presence of framing lumber on top ends up being the same thing.

Note - you can read the NFPA stuff at:
(broken link removed to http://www.nfpa.org/freecodes/free_access_document.asp)

 

[jeepin in maine]

so will the insulated thimble shown in your previous post work?
by looking at system b of the last diagrams you posted......it looks like maybe i can change the wall thimble to an 8"and use a solid insulated factory built chimney length?
what would you do if it was your dilemna?
thanks for your help.jeremy

 

[webbie]

Your situation fits somewhere in between all these, because of the solid masonry around it. As I mentioned, it might have been completely approved (9", when it was installed). Given those and other options (the insul-flues, etc.), I would guess that I might enlarge the hole, cement a piece of 8" ID insulated chimney in there, and then run the 6" pipe through that with either an airspace or kaowool around it. I think that would make a pass-through quite safe.

Of course, we have not talked about the chimney itself.......that is another matter all together.

 

[jeepin in maine]

ok........i think that the 8" id insulated chimney,with 6" run thru it will be easier to install than the insulated thimble(that sucker requires a 16x17 hole).so that and the double wall interior pipe should help with my clearance issues.what should my concerns be as far as the chimney?its in decent shape,mounted 1" away from the outside wall ,the flue joints as well as the thimble all appear to have been sealed with refractory cement,its up far enough that i easily have my 10' clearance,i get a decent draft,and i cleaned it before i started using it.the bottom block is solid mortar,the second block contains the clean out door,and the 3rd block is where the thimble enters.the slab its on appears to be about 10" thick.i was concerned because the slab is at ground level that frost my heave it around,but upon inspecting it we found no cracks,damaged mortar joints,or loose ties to the building.
a question.if i go with the 8" insulated chimney pipe thru the wall,do i just butt that up to the outside of the chimney block and run the 6" thru it into the flue,or do i need to enlarge the hole in the block and the flue to 8" as well?again.......thanks for the help

 

[webbie]

Chimney sounds OK.....yes, you would butt the insulated chimney piece up against the flue tile, and run the inner stainless steel pipe into the flue tile - just a little. If possible, reach in and cement stuff with refractory cement.

 

[jeepin in maine]

man.........you've been a tremendous help.i can't thank you enough.i'll keep you posted on how things go...........and i'm sure another question or 2 will arise thanks again.jeremy