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Bandrasco 10-26-2008 08:57 AM

Fire Brick Confirmation
Ok, I knew that things were going too smoothly to not have one of those 'oh crap' moments:eek:...

After reading a ton of threads on brick cutting angles, domes, mortar, etc. I saw where fire bricks should weigh around 8-10 lbs depending on what 'duty' you get. I know mine didn't weigh that much so I got out the digital scale and they weigh exactly 6lbs. Is this the wrong type of brick? I asked for fire brick, told them what I was building, they gave me what I asked for. Now after reading the threads I'm afraid to use them. I cut enough for the 1st row and floor, but left it at that. I'm ready to start cutting and building the arch but FREAKED OUT when I weighed mine. I'm ready to have a melt down...

Without seeing them can anyone tell me if they are in fact fire brick instead of insulating brick? I know it's kind of like telling the mechanic to diagnose your car over the phone but if it's black and white I'll load them up and be at my supplier tomorrow morning with a not so big grin on my face:mad:

Thanks everyone!

egalecki 10-26-2008 11:23 AM

Re: Fire Brick Confirmation
how big are they? some firebrick are not the same size as others- I know mine were a little on the small size- but I don't know how much they weighed.

Bandrasco 10-26-2008 11:30 AM

Re: Fire Brick Confirmation
Hi Elizabeth,

They're 9"L x 4"W x 2&3/16" thick. Sound right?

Thanks so much.

egalecki 10-26-2008 03:35 PM

Re: Fire Brick Confirmation
It may be that you have low-duty firebrick instead of medium duty. I think that would be ok, since the plans say to use low to medium duty ones. But I think you should check with the place you bought them to be certain, though. 3 pounds is a lot to be off on the weight. I don't know how much an insulating firebrick weighs, and the size of what you have isn't off much. That's about the size mine were.

Maybe someone else has a way to test the brick to see if they insulate or heat up?

egalecki 10-26-2008 04:36 PM

Re: Fire Brick Confirmation
I looked around the web, and most dimensions given are 4.5 by 2.5 by 9, so yours are a little narrow. I just don't know if the extra .5 inch would change the weight that much.

staestc 10-26-2008 08:28 PM

Re: Fire Brick Confirmation
I may be wrong, but I believe that insulating fire bricks are very light, like 2-3 lbs, not 6-8. I am pretty sure you are little lighter because they are a little smaller and you have nothing to worry about.

I think you could test one easily by heating it up in your house oven at like 500 degrees for an hour or so, then see how long it takes to cool off. And insulating brick shoudl cool over very quickly, as they don't hold heat nearly as well (or as much), while a non-insulating firebrick should hold a lot of heat and hold it for a pretty long time.

But really, if your bricks are 6 lbs or more, I would guess they are fine.

But then, this is a pretty permanent construction! So I would still go back to the vendor and try and get more information and tell them what you are worried about and why.

Wait till somebody else who really understands this stuff chimes in before you take anything I said to heart though, I am still new to this :)

Good Luck,

RTflorida 10-26-2008 08:51 PM

Re: Fire Brick Confirmation
If they are low duty - NO WORRIES, that is all that is needed for a Pompeii. If you don't mind my asking - who is your firebrick supplier? I'm actually in Oldsmar FL, I either called or visited every brickyard from Tampa/St Pete to Lakeland to Sarasota. I ended up at Cement Products & Supply in Lakeland...Low duty, fireplace bricks at 77 cents each (that was 20 months ago). The dimensions of your bricks are pretty close to mine (a little thinner and narrower than what others have found, mine were still in the 8 lb range though). The big issue is making sure they are not insulating, and at 6 lbs I think you are safe; I've never heard of insulating bricks in this size weighing more than about 2.5 lbs. Pretty certain you don't have heavy duty either - they tend to be the heaviest.

You mention using the cut face on the inside - not recommended by others on the forum. The outer surface is supposed to be the toughest and most hardened on any brick, with the cut surface being more likely to pit or spall over time.....not sure how true this, but when venturing into new territory (like building an oven) I tend to listen to those who have passed before me.
Hope this helps


Bandrasco 10-27-2008 04:40 PM

Re: Fire Brick Confirmation
Thanks RT,

I'm over in FishHawk in Lithia. I also went to most suppliers that I deal with, Cemix, Rinker, Fla Silica in Plant City. They all had the same bricks, FL Silica was the least expensive and say they are true fire brick but didn't know much more about them. I confirmed today that they're manufactured by Superior Clay and meet all requirements for this application. Their site shows that they are 'small' fire bricks at 9x4x2 1/4 and weigh 6lbs, the full bricks are 9x4 1/2 x2 1/2 and weigh 7.65 lbs.

You got a much better deal than I did however compared to most places I was able to get them about $.60 less at FL Silica. Great people over there as well.

I'm ready to start the dome! I see many shots where the first course is on the insulating floor with the actual floor inside, and then I see a full fire brick floor with the first course sitting on them. Any suggestions on which one is better? I'm going to start off with a half brick lying on it's 2" side and then go to half bricks on their 4' side flat around the dome.

Thanks RT,

dmun 10-27-2008 06:58 PM

Re: Fire Brick Confirmation
Both methods work fine. I built my dome on the floor on the theory that the horizontal bricks would spread the load on the insulation board, and it's a little less cutting since the ends can stick out from the dome. Others think that having a dome separate from the floor enables you to replace your floor when it wears out. I think this is more of a consideration for commercial ovens, I've never heard of any of our home builders replacing a floor unless they forgot to put insulation underneath.

staestc 10-28-2008 01:47 AM

Re: Fire Brick Confirmation
Are there expansion/contraction considerations regarding build the first course on the floor versus around the floor? I was wondering because when I was going through Ken's build thread today, I noticed that he used a cardboard spacer between the floor and the soldier course around it and I believe Hendo used a vinyl spacer for the same reason.

If you do build on top of the floor, do you mortar your first course to the floor bricks, or let that first joint float?


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