Michigan WFO

[mfiore]

Re: Michigan WFO

No luck here, Scott. I was hoping for slate. I like the look of a heavy roof on the stone oven, like Nikki's oven. Until I priced it. Very cost prohibitive. Seems no one in Michigan uses slate roofing.

[Lars]

Re: Michigan WFO

Mike,
I bet you could use 12x12 slate tiles for an area as small as a wood oven. I have seen pretty rustic slate tiles for fairly inexpensive at the home depot, lowe's type stores. Sometimes less that $2/sq.ft.

Just an idea.

L.

[dmun]

Re: Michigan WFO

There are lots of sources of used roofing slates:

Sources of Salvaged Roofing Slates

They show up on eBay, too:

slate roofing - eBay (item 270402181798 end time Jul-03-09 08:12:01 PDT)

11X16 ANTIQUE ROOFING SLATES, BLACK MUNSON, MANY 2 SELL - eBay (item 260365231632 end time Jul-19-09 18:30:20 PDT)

[smuth10]

Re: Michigan WFO

Mike,

I did some calling around today and finally found a place that carries pretty much everything. For the metal roofing he said you have to order a minimum of 1 sq or 100 sq feet. He said most of them where around $200 a square and they could have it in a day. Their headquarters is in Saginaw. They also have slate and composite slate that looks very real. Here is a link.

Wimsatt Building Materials - Distributor of Quality Residential & Commercial Roofing, Siding & Stone, Windows & Doors, Lumber & Composite Building Materials

I am planning on stopping by their showroom in Sterling Heights tomorrow to pick something out. Let me know if you want me to ask them any questions for you.

[mfiore]

Re: Michigan WFO

Thanks for the tips, everyone. Once again, this forum is invaluable!

Scott, I don't know how I live in a city (not large) and not know about that place. Never even heard of it. I'll be certain to stop in next week!

Thanks again.

[mfiore]

Cracked Flue tile - second time!

Getting frustrated

Friends over for the holiday. Fired up the oven for some pizza. As it was getting good and hot (although not too fast, over about 90 minutes), we heard a loud pop. At first we thought it was some firewood, but later learned otherwise.


The back of my chimney flue tile cracked vertically. I have a tapered flue tile on the bottom, which split right where I mortared the two pieces together. The 8x8 flue on top also split, however, right up the backside! I'm not sure why this is happening. This is the second time. The first was this winter. I assumed I heated it up too quickly from the cold. Clearly not the case now. Last time, it was just the bottom section. Unfortunately, I now have the steel framing up so fixing/replacing will be much more complicated.

Once cooled, the crack is just a hairline.



It looks like this has happened in the past to a few others on the forum (Christo?) but I don't see how it was resolved.

Any thoughts on the best way to repair this? Do I have to replace it all? More importantly, why is it happening and how do I prevent this from happening again? I don't want to enclose the whole thing, only to hear the dreaded "pop" again. Perhaps I need to rethink my chimney and consider a stainless steel system. I really hate the thought of that, since I've already done most of my framing.

[Lars]

Re: Michigan WFO

Mike,
I just cracked my first flue tile the other day!

I tried to get some advice, etc. and I had read about one guy here who replaced the clay tile twice! I decided when mine busted that I just don't really care whether there is a crack in it. I had not installed it... the store that where I bought it offered to replace it, and they also suggested using a high temp silicon caulk.

Well, knowing I COULD replace it was good news, but, really WHY would you? It is obvious that for an indoor oven, a person would just devise a firebrick transistion to stainless triple wall and go all the way to the roof with it. For an outdoor chimney, it really is just to take the smoke away from your face, right? There are no worries of a tiny bit of smoke getting out the back ( especially if you seal it up with some elastic caulk (which I may or may not do.)

I went ahead and mortared in my flue (crack and all ). The crack is nearly invisible when cool. I even made the same decision on my face brick and arch. I am going to fire the hell out of it and see where it cracks up. Then I am going to have an even bigger fire, get some fine sand mortar, a sprayer, mist the offending crack, stuff mortar in there and see how it looks when it cools down.

Long winded reply here, but, I know what you are going through, sort of. My standards may not be as high as yours ( I didn't take the time to make such a nice flue transition) ...NEXT TIME!!! ( it will be all stainless steel)

L.

ps. What part of michigan? I used to go to Mackinaw every summer, 36 years ago...man I must be old!

[dmun]

Re: Michigan WFO

I don't quite get the cracking flue tiles. Mine didn't crack, and I have a huge stack of them. These things have been standard in American construction for a century: My house is from 1910 or so, and has a dual flue tile lined chimney going up the center.

I'm wondering if the cracked tiles were still wet? Or if they need to be enclosed in masonry to work well?

I'm scratching my head...

[Lars]

Re: Michigan WFO

Dmum, ( Is it James?)

I think if you were to extract your flue tiles that have been in your chimney ( above a wood fire place) that you would find several that have cracked. That is only my guess.

Essentially, when the inside of a tube gets hot, and the outside is allowed to be cool ( open to the air) a great degree of stress is taking place in the wall of the tube if the outside is not expanding to the same degree as the inside, it will crack on the weakest spot. It may be that all this 'open air' testing is just a mis use of the clay tile, and that it may not crack if enclosed and the tube would then have a tendency to heat up more uniformly. I am guessing, here, but I did study physics and thermodynamics way back when. There are several things about this oven that make the whole project a learning experience... in many ways.

My daughter gets tired of hearing me say that this oven is like a real life thermodynamics lab. So... I will NOT say it again here..

It would be interesting to enclose a clay flue in a bit of vermiculite/portland and then see if it cracked under heavy fire. I think the flue crack, the arch buttress, and the importance of a physical break between the fire brick and any outside cladding ( dome, brick, stucco, etc.) are three problems that should be solved and put on a sticky thread for any newcomers to beware ( and use the proper solution method)



Lars.

[mfiore]

Re: Michigan WFO

Seems like the ones that cracked were all self made, tapered units. My crack started there. The one above is a direct continuation vertically from that joint.

I wonder if it would be better to have a full unit on bottom (untampered with), with the tapered unit above. That way the tapered unit is not exposed to the hottest part?

Keep scratching your head, please.

[Lars]

Re: Michigan WFO

Mike,
Nope.
Mine was a perfectly fine, 9x13 clay flue 2' long setting on the opening. The gases are hottest above the vent. If it is going to crack, the first piece will crack first. I had a taper in the arch vent ( firebrick) , and actually, the opening to my flue was a good 1/2" smaller all around then the inside of the flue.



Lars.

[dmun]

Re: Michigan WFO

Dmum, ( Is it James?)
I think if you were to extract your flue tiles that have been in your chimney ( above a wood fire place) that you would find several that have cracked. That is only my guess.

It's David, by the way, Dmun is my father's old fraternity nickname, from his first initial (All Munro men have D first names Douglas, Donald, David etc) and the first part of the last name.

I think all the flue tiles that cracked have been fired before masonry chimneys were built around them. Code specifies a half inch of air space between the flue tile and the masonry enclosure. My split cone flue tile, the hottest part, was covered in refractory blanket and buried in perlite concrete, up to the level of the support slab above the oven, and the tile stack was provided with the airspace between the flue tile and chimney above that.

I've always held that the firing of bare domes contributed to cracking, but my brick dome cracked too, and it was insulated and cured for the better part of a year before the first fire.

All the flue tiles that have cracked were fired out in the open, as far as i can recall.

[Lars]

Re: Michigan WFO

David,
Of course, Dmun makes one think of 'demon'. For some reason I got you confused with someone else, sorry about that.

I think the tiles being 'out in the open' and cracking may be a clue. I think the bottom line on this issue is that the oven dome WILL crack, the vent/arch WILL crack under heat, and the flue may or may not crack. The solution, as far as my next oven ( if there were to be one) would be to isolate the inner (firebrick structure) with loose vermiculite or blanket from the outer structure, and then let it crack.

I purposefully buttressed my firebrick arches with my outer brick. I just underestimated the amount of heat and expansion the arches would see. I think if I had it to do over, I would have buttressed them with firebrick, or re-built them, THEN do the outer arch and enclosure with at least a 1/2" space and NO physical connection between.

Today I am taking my Harborfreight thermometer out for a small fire to get an idea of temperatures. Should be fun.

I just went ahead and bricked it up, knowing that the crack will likely open up again when fired. I think there may be a way to fill the mortar joint while it is up to temp... not very sure, though. ( see attached pic)

L.

[mfiore]

Re: Michigan WFO

All the flue tiles that have cracked were fired out in the open, as far as i can recall.

Sounds reasonable. What do you think I should do at this point?

A) tear it all out and put in a fresh one (painful)
B) Try to patch with more heatstop
C) Use some furnace cement (is that the correct stuff people have used for the dome cracks)
D) Tear it out and put in a stainless steel one
E) Cover it up and ignore


???

[mfiore]

Re: Michigan WFO

All the flue tiles that have cracked were fired out in the open, as far as i can recall.

David,

I thought about that some more. If there is usually nothing but air between the flu liner and the masonry throughout the chimney run, then why do you suppose it makes a difference if the flue tiles were out in the open or exposed?

Mine, for example, was out in the open for the firing, but has been covered secure and dry under tarp all year long. It's not wet.

Also, I don't intend on building a true masonry chimney. I am framing a box around to install stone veneer. I don't know if that makes a difference.