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wg_bent 08-03-2007 12:51 PM

Brick type and concrete test.
There has been a few discussions on using plain red clay bricks on this forum, and I personally was wondering about this. Well, here's the scoop.

As documented in another post, I built a temporary oven similar to the temp one seen on the brick oven pages. I used some patio blocks and some red clay bricks. the oven was used a few times for cooking, but in all honesty it was quite inconvenient due to it's height and size, so it ended up being a very good backyard brush disposal fireplace and marshmallow cooker. Last night I needed to move it due to a tree company coming over to drop a huge oak in my yard.

Here's the punch line: Both the red clay bricks and the concrete patio blocks (they sort of look like cinder blocks but just 1.5 inch thick) were extremely brittle and broke very easily. This is after about 10 firings.

The point I'm making here is that it's clear that if building a permanent oven, firebrick is essential and spending the amount of time it takes to make a proper oven shouldn't be wasted using any morter or brick material that's not intended to take the high heat a oven can produce. Hopefully I helped someone avoid a mistake.

james 08-03-2007 04:29 PM

Re: Brick type and concrete test.
Very interesting and helpful. Thanks for that. I think this is the first I can think of someone firing and then disassembling an oven, and then actually looking at the bricks.

Let's keep track of this experiment. Thanks.

dmun 08-03-2007 07:05 PM

Re: Brick type and concrete test.
This is an important experiment that confirms conventional wisdom. You would expect that the concrete patio pavers would break down quickly, but not that the red bricks would, so fast. Thanks for letting us know about this.

James, why not make this thread sticky, under the firebrick listing? It answers a question we get asked all the time.

RTflorida 08-03-2007 08:21 PM

Re: Brick type and concrete test.
I will second that.....I'm sure this will give the frugal or tight budgeted builders something to think about. With all the hard work that goes into an oven, I certainly would not want to be faced with crumbling bricks...I would beg, borrow, barter (thinking of Nick - HAPPY BIRTHDAY!), or save a little longer in order to do it right the first time.

nissanneill 08-04-2007 03:43 AM

Re: Brick type and concrete test.
...............and then there was Russell Jeavons ovens made from 'pressed reds', still fine with no spalling or cracked bricks after 4 years of commercial use!!
Guess we have better clays down here for proper brick making.
Can't think of any other reason.


maver 08-04-2007 04:56 AM

Re: Brick type and concrete test.
well... remember that this temporary brick oven was not mortared. It's possible Russell Jeavons' bricks are also more brittle after heat/cool cycles, but unless the oven were disassembled we wouldn't know if it were brittle. And the dome (or even arch in a barrel oven) shape's inherent stability plus the bricks being wrapped in mortar on all but the oven face reduces the worry about bricks just falling apart. Spalling is probably still the main concern. But I'm glad I had firebricks available.

Bacterium 08-05-2007 08:50 PM

Re: Brick type and concrete test.
My "pressed reds" oven (Redgum Roarer) has had about 12 decent fires and no signs of spalling at all......yet I'm open to the situation that one day it may happen :cool: maybe not

The base of my oven arch (opening bit) extends into the oven dome by a small amount which means I could chip off some of the back edge of a brick (out of sight). Seeing that I have also also kept a couple of these red bricks(not used in the oven build) I could make a comparison between the 2.

I think a key part of what helps it last is that only fired ends of the "pressed reds" are exposed (inner dome).....not the cut ends.

Sure fire brick is the best bet for your oven dome.....however under some conditions and with some disadvantages (eg. heat up time seems to be about 45mins longer) "pressed reds" are possible

barbarian 09-14-2007 01:31 PM

Re: Brick type and concrete test.
that's great information because like many newbies, that was my first question...
"can I use red clay bricks ??" :D

I read a lot about them and it seems the overall idea is that it is best not to use them however I think of all the ovens that were built in the old days used clay and clay "baked" bricks..
also I just returned from a country (panama) were they also use a local clay from the town of L'arena their ovens are quite efficient and even their homes are made with the same clay :) they use concrete blocks for the base and fill
to the top of the hearth with dirt and stones the hearth is one layer of homemade clay bricks as mortar they use the same clay used for the bricks to bind the dome , I have seen both round and barrel shaped ovens and they are built in a couple of days .. I do have some pictures and I will make a thread about this asap...

Unofornaio 09-15-2007 12:03 PM

Re: Brick type and concrete test.
I have had a different experience with red bricks in an oven. The test oven I built at my old house was an AS design sort of and I used reg clay reds in it. I used it for years with not spalling on the surfaces or breakdown what so ever. It was built with just fire clay and Portland and held up fine.. these were new bricks, just commons, nothing fancy. The hearth was firebrick. That oven was in use every Friday and Saturday in the beginning for well over 8 months then every Saturday after that for almost 3 years.

But the thing is if your gonna build an oven the difference in cost really is not so bad. Although the firebrick are more money they are also larger and what the price difference is .45 vs .70 plus you are using a brick that is specifically made to take the heat. The fire brick are the way to go..

RTflorida 09-15-2007 01:47 PM

Re: Brick type and concrete test.
I have to side with UNO. I understand budget constraints but in most areas of the U.S. firesbricks are under under $1 (usually the 70-80 cent range).
$50 or $60 additional is nothing for a product that is designed and engineered for the my opinion. If your goal is a 'green' oven (using nothing but recycled materials), that is a different story. If your going with store bought - get the right product for the job. Again my opinion

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