Second broken Flue Tile

[Dave M]

This is slightly off topic, but related to clay flue construction: When installing a clay flue can you just wrap it in insurfrax type insulation then apply stucco directly to the insulation surface (wrapped in wire of course)? Or does there need to be an actual air gap around the flue pipe?

[Pannabecker]

From looking at the many pictures posted on this website it looks like many people wrap their flues it the blanket insulation. I'm wondering, if the oven is freestanding, nowhere near a house, does there need to be any insulation at all between the flue and brick chimney, or just the air space. Karen

[maver]

Code allows for an air gap as the only insulation in the chimney run with a brick surround - this is ok inside or out. Mine is an outdoor, and it's built with flu tile, an airgap, then a brick surround. Inside you have to be careful about clearance to combustibles, but the brick surround would usually provide the clearance you need.

Marc

[Dave M]

What do you do if you're doing an igloo style enclosure and plan to stucco up the flue? I was thinking I could use 1" insulation blanket wrapped in chicken wire and apply about 1/2" - 3/4" thick stucco layer over that.

[Dutchoven]

I didn't get to the last message of the thread...boy I hate that ...answer a question that has already been answered. I might suggest using a larger diameter flue tile if you're using clay and set that outside of the first with the insulfrax in between.
Best
Dutch

Dmun is correct as far as the many that I have had the chance to look at. The space is to allow the flue liner to expand and contract within the outer shell of masonry, as well as to allow it to be heated separate from the external masonry and that helps the draft. Sometimes the space between is filled with loose ceramic fiber or some other higher heat insulating material. To the best of my knowledge the pieces are connected to one another and there usually are codes governing their construction in earthquake zones.
Best
Dutch

[Unofornaio]

I will try to help if I'm not too late.

From the first post:
"I'm also trying to figure out a way to enclose it with the space allowance around it. It's so close to the front of my oven and doesn't allow for a gap around the flu and then block to enclose it. I tried to attach pictures but I'm having a hard time figuring out how to do so. Once I place the flu on the fire bricks there is only 2 inches of space to the front wall if the enclosure, not enough space for the 1/2 inch air space and a brick or block. Any ideas?"

It sounds to me the oven is really close to the front of the support slab and you have run out of room is this correct? at this point forget about how to do the flues and concentrate on what all that is going to rest on (3 sections of liner covered with brick) is A LOT OF WEIGHT get some pictures in here so we can see. A metal flue liner would solve both problems weight and space... and yes a bed of mortar is all that connect the flue liners

Karen- Fires before the surround is put up (some guys do it) is to cure the fire clay and check for leaks. Liner close to the chimney brick ok touching not so good.

Dumn- The flue and surround is built at the same time leaving the desired air gap as you go. Otherwise you would need to build the scaffold twice and some of the ones I was on as a kid are up there, 5 and 6 frames.

Dave/ Karen you both asked if you need to wrap the flue with insulation and the answer to that question is a resounding NO there is simply no need for it inside or outside oven.

Dave you also ask "What do you do if you're doing an igloo style enclosure and plan to stucco up the flue? I was thinking I could use 1" insulation blanket wrapped in chicken wire and apply about 1/2" - 3/4" thick stucco layer over that."

Again there is no need to do this outside and inside I'm pretty sure it would not pass code. If you are asking will work to stucco it this way? Yes

Now if you guys are calling the "throat" a chimney "Chimney" to me means the pipe or masonry that sits above the vent/throat opening. If its the throat then I believe wrapping this area with insulation is a good thing because its still really part of the oven. The throat of the oven or a fire place is the transitional area where the gases and smoke leave the oven/fire chamber and enter the chimney. I will have to look through the other threads, if thats how most are refering to the vent/throat area (calling it a flue) then Im sorry I didnt catch that.

[Dave M]

Uno, thanks for the info. I am asking about an outside installation, and I'm talking about the chimney not the throat. I'm sure this has been answered somewhere else ont this forum but we're sort of the the topic so I'll ask here anyway. Your saying for an outside install, using clay flue liner as the chimney, it's ok to stucco directly onto the flue? This won't casue any problems with the flue expansion & contraction from heating and cooling?

[Unofornaio]

You know Dave to be honest I'm not 100% positive but if you are going to wrap the liner in insulation first I would think this is going to absorb what ever expansion is going to happen.

In my previous post I honestly was not thinking of the expansion factor just simply that the stuccoing this way would work. However I do think with the insulation wrapped around the flue liner it would work and not crack but again I'm not 100% its just an educated guess.

I apologize if my previous was misleading. I try to be real cautious of making statements that are not experience based and or well thought out, I can see how my statement is guilty of both. Sorry about that.

[Pannabecker]

I guess I have the air gap figured out. The problem wasn't that I don't have any extra space in front of my oven. I have lots of extra space. I even went bigger than I needed. The problem was fitting an 8x8 clay tile flue liner on top the oven with room to brick around all over the vent area without hanging over the arch.

Heres my question now. I am concerned about the weight of the 3 sections of clay flue liner. What would happen if I just used one section of the clay liner, surrounded by fire brick and then just continued the rest of the chimney with fire brick several feet higher without the clay liner in it?

I've tried to attach a picture but the file was too large for this forum. I can't figure out how to reduce the size of my file. Karen