Using rock instead of brick

[josh_r]

Hello all

I am planning to build an oven for my wifes father. We live in on the south end of Lima Peru. Due to the lack in quality of bricks here, I am thinking of using rock instead. The brick here is very brittle. I am guessing that rock would work the same as brick would, but with the higher density of rock, it would take a little longer to reach temperature, yet would hold the temperature longer. Would this be correct? Has anyone here built one out of rock? I also have to find a material here that will work for the floor and work as insulation. I was thinking about a rock floor with a thin layer of sand and I can place flat tile as a base and it can easily be replaced when it breaks as I wouldn't expect the tile to last long. Things here in Peru are not made with the same quality as they are made in the states and other countries. Any advice would be awesome!

Josh

[mrchipster]

Re: Using rock instead of brick

Have you tried to visit a local pottery and see where they get bricks for their ovens, I am also sure you must have some local foundries that also may be able to source brick, commercial furnace companies would also use fire brick. Not the guys who do home heating but the ones that do heat plants for big buildings. Try to set up a meeting with the facilities manager for a bigger company and pick their brain.

The wrong type of rock could explode at worst or spall quickly. You may be better off with a well built cob oven and spend just enough to get brick for the floor.

[josh_r]

Re: Using rock instead of brick

Thank you for the reply Chip. I am afraid that there are no good brick manufacturers in Peru. the standard here is incredibly low. The bricks they make here fall apart after a few years being exposed to the climate in Lima. The terra cotta bricks they use for building are incredibly weak and are hollow. There is absolutely no need for high quality brick here in any trades, so they simply do not make it. It is very very difficult to get Peruvian companies to make anything of quality I am finding out. This is why I asked about using rock. I have also thought about making m own adobe bricks and firing them to strengthen them. Comments?

[brickie in oz]

Re: Using rock instead of brick

Hi Josh.
Get yourself some local rocks, build a fire around the rocks and slowly increase the heat of the fire, if you increase the heat too soon the rocks will fracture, but may not if you take it slowly.
The rocks will fracture if you just chuck them in the fire too which is why you would have to take it slowly.

Choose the rock type that does not fracture or explode with heat, most igneous or volcanic rock should work out ok, sandstone may be good too as it has no crystal structure.

[mrchipster]

Re: Using rock instead of brick

I have also thought about making m own adobe bricks and firing them to strengthen them. Comments?

Instead of making adobe bricks just go straight to the cob dome. Adobe brick is made from identical materials search cob ovens on here there are several people who have done them and they can help you out. I have not done one so I am not a good resource.

[stonecutter]

Re: Using rock instead of brick

Choose the rock type that does not fracture or explode with heat, most igneous or volcanic rock should work out ok, sandstone may be good too as it has no crystal structure.

Actually Al, igneous stone will be more susceptible to breakage during thermal cycling, especially granitic types with a high quartz content. Sedimentary may hold up better, but useless there is some wondrously durable kind in Lima, I think the surfaces would become friable after a relatively short time.

I think Chip is onto the right solution here, and I will add to it that the OP should seek a clay source....maybe a potter or a natural deposit.

Save the stone for the finishes.

[Tscarborough]

Re: Using rock instead of brick

Crappy soft brick will make a fine oven, rock will not.

[josh_r]

Re: Using rock instead of brick

Thank you all for the replies. This gives me a much greater idea of the direction I should head. As for the soft brick here making a fine oven... If it can't make a fine wall, how is it going to make a fine brick oven? The walls they build out of brick here can't even withstand the mild climate here. They crumble into nothing. I just cannot see these bricks holding up to the extreme temperatures and expansion/ contraction as a good brick can. You are never going to know what I am talking about unless you see it for yourself... Maybe I will take a picture for you guys some time.

So it sounds like my best option is to look into the cob ovens. Thank you all very much. This is a great informative group!

Josh

[Tscarborough]

Re: Using rock instead of brick

I know exactly what type of brick you are talking about and even how they are made. What kills brick in the environment is water and cold, neither of which should be an issue in an oven.

[josh_r]

Re: Using rock instead of brick

Have you seen the brick in Lima?

[ogorir]

Re: Using rock instead of brick

Looks like there's some decent production is Cusco : Energy efficiency for brick producers in Peru - YouTube

I think you need to do a bit more looking before you write off an entire countries brick production. You should still be able to find some form of fire brick, kiln lining, or even large flue pipe you could break up. Also remember that the brick you see making walls(and crumbling) isn't the brick (ideally) you want to use in your oven anyway.

[david s]

Re: Using rock instead of brick

When traveling in Europe a few years ago we saw lots of ovens that had been made from stone. Most of the stone ones were in castles, looked pretty rough on the inside, but must have been hundreds of years old. Don't know what kind of stone was used, but the interiors looked pretty good and looked like they'd be still usable. If you source your material locally and it's free, then all it costs you is your own labour.

[josh_r]

Re: Using rock instead of brick

Here is the problem with your suggesting products from cusco... I live in Lima which is 2 days drive from cusco. It just doesn't seem feasable to drive to cusco to get bricks for an oven. The problem with Lima and the trades here is once they get established in doing something a certain way, they never change it even if it doesn't work so well. If you have never been here and seen it, you will never understand. I am not here to get intoo a debate about a country however. I am here to learn about building a brick oven and what to look for in a quality brick.. that way if I do happen to find good bricks here, I will know that I am looking at and won't assume they are like the other crappy bricks. Also, I came across a plaster company page that shows a photo of a brick wall built with cement on the bottom and lime plaster on the top. The brick touching cement has completely started to crumble. The brick touching lime plaster are perfect. What are your thoughts on this? Would lime plaster hold up in an oven? I am not sure I can even find lime plaster here...

[josh_r]

Re: Using rock instead of brick

ogorir, I just watched that video... Those are exactly the kind of bricks I want to avoid and the most common type of brick made here. They use them for building homes here. They are very fragile. The only use I could see in an oven is to use a layer underneath the floor of the oven to aid in an insulation layer. the hollow bricks could be filled with an insulation material and then have good brick stacked on top of them. Any thoughts on this idea? Would that work?

And please don't think I am being a negative nancy. I am just a bit confused here as to what I should be using down here. there are not the same resources here as there are in the United States, Europe, Australia, etc. This is a 3rd world country. I have to be creative, yet I dont wan't to build something that doesn't work or falls apart and waste the money and time put into it.

[Tscarborough]

Re: Using rock instead of brick

The brick under the portland plaster crumbled because portland plaster is not a breathable membrane, lime plaster is. As I stated, those brick are fine for any purpose where they will not be exposed to wet and wet/cold conditions, like in an oven or in a lime plastered structure.