Thinking about bricks for my build

[leeb]

I'm a new member trying to plan my build, I've purchased Russell Jeavons book. In it it suggest that fire bricks are a waste of money is this really the case ? If so can someone tell me if they have built with normal bricks and if so which type/make/material did they use.

many thanks leeB

[tapir]

I guess firebricks would be a waste of money if you didn't use them in your main firing space. Seeing as they're designed to take high firing temperatures and retain heat, I can't see how they could be thought of as a waste of money.

[leeb]

Ok I worded that wrong, russell's book says you dont need to use fire bricks as fire bricks are actually for kilns and 1000 degrees plus heat, where as your WBO will not normally exceed 700 degrees in which case normal bricks would be fine. Didn't mean to offend just looking for advice

[tapir]

No offence taken!! Apologies if my reply seemed harsh.

I've gone for firebricks in my BVO because I trust them over ordinary bricks - they're designed for a particular purpose.

If you're going to use ordinary bricks, they have to be consistent throughout, eg same material all the way through.eg some modern bricks look like red bricks but chop them in half and they are 75% something else.

[leeb]

Great thanks Tapir good point

[bookemdanno]

The historical oven builds were before firebrick was invented, along with OPC.

Old solid red bricks were used by Vic in "Vics Build", a pompeii in the archive section.
I too have a massive pile of Old Reds from a Victorian barn, which i'm gagging to get amongst for my build.

Firebrick is the top spec option, i'd say, if you don't mind paying the money for the peace of mind. Just stay away from modern bricks, unless perhaps Class A Engineering, and definitely do not use concrete bricks.

[tonyb]

Its not just about the maximum temperature (I think 700 (F?) is low by the way), its as much about the effect of the thermal heating/cooling cycle. Firebricks and ceramic materials in general are designed to be used for this type of thermal duty, normal bricks aren't.

There are potential negative, thermal and mechanical implications of choosing ordinary bricks over firebricks as well as positive financial implications. Those negative risks are greater for modern bricks in general due to lower firing temperatures whereas victorian bricks were generally fired at higher temperatures which seem to make them more suitable to wfos.

The main risk with using ordinary bricks is spalling, which is where bits break off. I'm not sure what the cause of this is whether its air pockets in the bricks or something to do with different expansion rates of brick material or other. This might also affect the mechanical strength of the bricks in the dome but I suspect the intrinsic mechanical strength of the dome design probably means this wouldn't be a major problem. It would be a major problem replacing/repairing the internals of a pompeii or barrel wfo.

[dodders]

I visited Vitcas in Bristol and had a good chat with 'Mr Vitcas'. My plan was to effectively render the inside of my oven with fire proof render 20mm thick ( I have cunning plan for doing this) and then use red clay bricks to form the dome so the render would provide a layer of protection. He suggested that this was o.t.t. and told me that red clay bricks have been fired to a very high temp under controlled conditions and so the danger is thermal shock, i.e. a rapid increase to a high temp will damage them, otherwise they should be fine and that the sort of temps acheivable in an oven are unlikely to damage red bricks. Fire bricks will not be affected by thermal shock and are better but $$.

[cannyfradock]

Hi Lee....here's my twopennethworth on the subject.

I would always go with fire-bricks as a first option.....and if the budget allows. Fire-bricks are not all the same and come in various different grades depending on usage. In our little world of wood-fired-oven the fire-bricks to buy are have an aluminium (or alumina) content of around 42%. The type of bricks used for kilns have a much larger alumina content as they serve a similar but different purpose.

There are pro's and con's in using normal clay bricks. The pro's are that if you can get your hands on reclaimed full old red clay bricks for nothing (they're very often thrown in skips on referb jobs), then all the better. The con's are that they won't work as well as fire-bricks, but if your oven is just for pizza parties the the difference should be very minimal. As Tony has mentioned, they have been known to spall.....or the face crack or flake after continued firing.

n.b....when I built my first Pompeii I used a mixture of full reclaimed reds for first ring of bricks, then used class b engeneering bricks for the rest of the dome. Not knowing any different at the time, the second full firing was when the dome was still quite wet...I fired it hotter than the devils own festering arsehole.....the outside render cracked but the bricks held firm and didn't spall.



Many of us have gone down the "economical" route of building a WFO, but apart from an arch which didn't have a curve...failing, and problems with a hearth which didn't heat up (due to laying bricks on cold concrete) all the builds on a shoestring have done well......I would still strongly advise that the hearth be fire-brick on top of an insulation layer.

Dodders (hello).....not so sure on your cunning plan. I don't think it will work (the render that is)....please create your own thread so we can follow your build.....thanks

Terry

[h12rpo]

But how many (ish) bricks do you need for a Pompeii (std 36 size) dome ?

I think it would be a good idea if we had a thread which listed materials quantities, I know they vary a bit between builds but just to get the general idea

[cannyfradock]

Quite right.....we should have a thread with the basics for each type of oven......we'll get there one day. In the meantime ....On my 36" pompeii (the last 2 Pompeii ovens).....I laid the hearth bricks on flat (3")......laid my first coarse of the dome "on edge" with half bricks.......and the rest I laid flat (again half bricks)...I didn't use fire-bricks on the chimney, nor the external arch.

.....I ordered 130 full (9"x4 1/2"x3")....and 5 (9"x4 1/2"x 1"....for arch transition). both times I ended up having about half a dozen bricks left over.

I don't know if I'm doing anything wrong, but many members have needed more bricks to achieve the same diameter of oven.

Hope you get some more feedback on the quantities needed.

Terry

p.s.....I also lay my fire-brick hearth Inside the dome.

[h12rpo]

I noticed that from your photos - how are you getting he required curve on the hearth edge Bricks .though? Or are you cutting them straight (angled) and filling the slight gap with the homebrew?

[h12rpo]

Bump for Terry's attention

[faz]

My floor is inside the dome too. I cut the floor bricks fairly crudely, I think typically each one had two cuts so that it fitted inside the circle. You can leave a smallish gap anyway which can then act as an expansion gap as the oven heats and cools.

[cannyfradock]

H

I missed your last post......good bump.

I did exactly the same as faz. Most of the bricks were cut straight with a hammer and bolster and some had 2 cuts in the same fashion. If any are rounded after cutting you can always "dress" them with a brick hammer.....hammer and bolster. I loosely filled my gap with the dried homebrew rest from laying my first course.



Faz has left a gap. This gap will eventually get filled with ash, but will still have room for expansion.....I will keep that in mind on my next build. It seems a good idea.

Terry