New Chimney Construction Questions

[leeave96]

I have an old chimney that I want to take down and replace with a new masonary chimney.

I have a gas furnace hooked to the existing one, but need a second flue for a wood stove.

I am interested in taking down the old chimney and replacing it with a new chimney that has two separate flues - one for wood and the other for gas.

I might want to tackle this project myself - but I don't see a lot of "how to" info/links for this kind of work. I see all kinds of stuff for lining an exting chimney, but not for building a new one.

I am kind of set on a masonry chimney, but have another question. If you can re-line an old chimney with a stainless steel liner and you can construct a chimney with double wall (and I have seen triple wall) stainless steel pipe, can you build an interior chimney with double/triple wall pipe and wood frame it in? My chimney would be an interior one vs exterior on the side of the house. For some reason, I don't get a warm fuzzy feeling about a liner inside a wood framed chimney - but it could be I am too old schooled in my opinions.

Any tips, info or links would be appreciated.

Thanks!!
Bill

 

[begreen]

A wood framed masonry chimney is going to need an air gap from combustibles, same as a stainless one. Personally, I'd put in a stainless flue system. A masonry chimney is going to need an air gap from combustibles, same as a stainless one. The SS chimney is very safe following the manufacturer's clearances or if you want an extra measure of insurance, exceeding them. And yes, you can enclose them with sheetrock or wood as long as the clearances are honored. Don't forget to have a firestop per floor penetration.

 

[70marlin]

I'd stick a direct vented water heater out the side of the house. then you's only need to set up for one chimney.

 

[bsticks]

Masonry chimney construction is pretty straight forward once you get out of your head "how am I going to do this?"

I built one 25 feet high to accomodate my wood stove in my basement. My first deal was to get all the way down to the foundation footing and pour a form. If you are going to do two flues, your are going to need a decent size foundation form to accomodate each flue side by side with the recommended air space between the blocks and flue.

Your city/township construction department might have some information to give you to review. My stoves user manual actually had a masonry chimney construction picture to get me rolling along.

Also, chimneys in some municipalities make you keep the chimney about 1 inch off the main home. So, if there is a fire in the chimney that can't be put out, they can easily push the chimney over.

Absolutely floored on that one when I heard it and verified it.

 

[firefighterjake]

Masonry chimney construction is pretty straight forward once you get out of your head "how am I going to do this?"

I built one 25 feet high to accomodate my wood stove in my basement. My first deal was to get all the way down to the foundation footing and pour a form. If you are going to do two flues, your are going to need a decent size foundation form to accomodate each flue side by side with the recommended air space between the blocks and flue.

Your city/township construction department might have some information to give you to review. My stoves user manual actually had a masonry chimney construction picture to get me rolling along.

Also, chimneys in some municipalities make you keep the chimney about 1 inch off the main home. So, if there is a fire in the chimney that can't be put out, they can easily push the chimney over.

Absolutely floored on that one when I heard it and verified it.

Hmmm . . . first I ever heard about designing a chimney to easily be pushed over . . . then again I haven't seen a chimney fire that couldn't be put out if caught in time. Are you sure that 1 inch gap wasn't to meet clearances to combustibles . . . that would make more sense as this would help avoid pyrolysis.

 

[billb3]

Masonry chimney construction is pretty straight forward once you get out of your head "how am I going to do this?"

I built one 25 feet high to accomodate my wood stove in my basement. My first deal was to get all the way down to the foundation footing and pour a form. If you are going to do two flues, your are going to need a decent size foundation form to accomodate each flue side by side with the recommended air space between the blocks and flue.

Your city/township construction department might have some information to give you to review. My stoves user manual actually had a masonry chimney construction picture to get me rolling along.

Also, chimneys in some municipalities make you keep the chimney about 1 inch off the main home. So, if there is a fire in the chimney that can't be put out, they can easily push the chimney over.

Absolutely floored on that one when I heard it and verified it.

We have to have chimneys anchored to the building here .

 

[bsticks]

Hi there,

As my progress was moving along building the chimney, the thin anchor straps were mortared into the block and then nailed to the 24 gauge rolled flashing against the home. There was a 1 inch space away from the home and specified that it is built this way in case of fire. Now, if the house is burning and the chimney is in the way, there would be good reason to pull it down. So, as it was explained to me by the Fire Marshall.

Another thing, I built my chimney using individual blocks and not chimney block because I packed sand inside the block spaces and 3/4 crushed stone around the clay flue and inch below each flue joint. I then poured concrete around each joint to keep the flue solidly in place.

But, irregardless my code is what it is.