Cristobal Cristo

We have finally finished our bread stove/smoker/cooker.
It started as a dry stacked hand made red bricks with massive gaps, no insulation and extremely quick heat loss. We had to bake on the bed of coals to eliminate soggy bottoms. However it served us for a year.
In 2024 I have poured the foundation, built the pedestal, poured perlite concrete and built 4 courses of the firebox. Then I had to focus on other projects.
In spring 2025 I have built the vaulted ceiling of the firebox and finished the smoking chamber.
In summer I have poured clay perlite on the top and welded the frame. Then in late summer the external walls were built. Then we installed the doors and my son has plastered and whitewashed the walls.

The design is an equivalent of a 20 cm BBR, but with a rectangular afterburner : 40x10 cm. It develops double vortes easily, even with the  port depth of half a brick (114 mm).
The floor is made of two layers of brick. The top layer is dry stacked in the firebox and the afterburner, so they can be replaced if needed.
The bottom is insulated with 16 cm of perlite concrete and one layer of insulating firebricks.
The sides have loose perlite - 10 cm thick and the top of the firebox clay perlite also 10 cm thick.
The ceiling of the skin is made of adobe pavers set on angle bars.
The chimney is flush with the ceiling, so I can easily protect it when it rains (no protruding object).

We have started it yesterday and since it was dry bone by the summer heat, we went full blast. It roars and burns extremely cleanly - at least for the eye.
We have burned two batches of eucalyptus. I have closed the chimney and then we baked two breads and two casseroles. In the top chamber we cooked 8 liters of potaje in cast iron pot. Yesterday the top chamber was too cold for any bakinbg operation, but in the morning the top was hotter than he bottom after the heat travelled overnight. The purpose of the top is to smoke and to cook stews/soups. I suspect that with continuous firing - at least once per two days, the top will develop pastry baking temperatures.

I have used:
120 l of 20 MPa concrete for the foundation (with 12 mm rebars)
30 adobe pavers and 25 CEB blocks for pedestal
around 220 firebricks for walls and floors
55 wedge #2 brick for vaults
1.5"x1.8" angle bar and 1.5"x1.8" flat bar for the frame
420 red bricks
10 Pacific Clay firebricks for external arches( I cut them into wedges)
12 Pacific Clay splits for the chimney
1.5"x3/16 angle bar for the ceiling
12 adobe pavers for the ceiling
Spanish thin bricks fro the cornice
0.6 mm stainless sheet and M6 stainless screws/nuts for the door brackets
2 Hubos two winged doors (needed to blacken them with linseed oil)
Almost all masonry materials were purchased used or were leftover from other projects.
For the firebrick joints I was using mesh 20 sand and local clay. For the outside bricks - the same local clay but with coarser sand. And for plastering the mortar with straw.
Limewash was prepared from high calcium putty.

There a was of cutting involved, but since I have 3 masonry saws of various sizes and multitude of grinders and diamond tools - it's always a pleasure.

Stephen B. Thomas wrote:Beyond that... If you are covering your shipping container with anything heavy, I strongly recommend you reinforce the walls and roof that will be covered so as to prevent buckling and failing of the steel. It likely won't break, but it will very likely bend and buckle without supports.

In this case what is the point to use the shipping container with all its limitations?

Fox James wrote:Hi Nina, I dont  think you will get anywhere near 1000c under your top plate, maybe 500c at peak burn.

I wanted to say the same
The masonry stoves I grew up with were all coal fired so it was easier to get higher temps and the heat was more condensed due to the stove design.
Sometimes the plate would start glowing in the center - indicating 500-600 C temperature which they withstood just fine.
Also not all cast iron has the same quality. I was using some Chinese made hot plate sold by some popular brand. It was placed on my outside experimental stove and developed a long thin crack (all way through) after a tennth fire.
Glass sounds good too and as a side effect you can look inside from above!

Daniel,

How the second floor is constructed? Is it a reinforced concrete slab or you will have to install some wood or metal beams?
Traditionally two level masonry homes had wooden ceiling on which wooden floor would work the best. They could also have vaulted ceilings built from bricks or stones and tiles would be used. In more modern times they started casting reinforced concrete slabs.

Being in hot summer Mediterranean climate I would avoid wood as much as possible due to fire risk.

Nina Surya wrote:Somehow I'm convinced the bell should be covered with one single plate.
Have you tried two plates next to each other? If so, how did it work out for you?

These plates are designed to work in an assembly of usually at least 2 or more in the cooking stoves where the fire is hitting them from the under. The perimeter of the plates is sealed with refractory wool (in older times they were just laid in the bed of clay I think). They join to each other with a protruding lip. Hot gases are supposed to go the the lower pressure area which is the chimney exit. I grew up with plates like that and I do not remember any leaks or smoke coming through the dry joints never ever. I have some brand new ones that I'm going to use on my kitchen stove so I can send you close up images if you like.

Nina,

Were you considering purchasing two plates?
For example this one:

Hubos cooking stove plate 600x310

They have a lot of other sizes, but not 600x600. Smaller elements handle expansion better than a big one.
I doubt that there is a better selection of cast iron masonry heater/stoves accessories anywhere on this planet.

It's a wide topic. Concrete probably is not necessary, but easily helps to reinforce/renovate something that was not build to last. Probably the simple shed was built by someone who did not think about the long lifespan of the building - probably the foundation was inadequate, the walls too thin, etc. Like for example building an adobe (or rammed earth) wall 20 cm thick and too tall and expecting that it will last for centuries. The same for stones that are too small/round and joined quickly. If the foundation and roof allowed for water penetrations eventually it will crumble sooner than later. Also Alpujarras is in seismic zone that will help to disintegrate buildings not sturdy enough. Old (and natural) buildings that survived all of this usually have very thick walls, buttresses that help to resist the forces, very thick timbers and good design.

You already have reinforced concrete frame so now you can choose the infill material for the walls.
You could:
-use modern Porotherm - natural clay and insulating then lime plaster it
-rammed earth (tapial)
-regular bricks - you could build two-wythe wall and fill the cavity with natural insulation; Spain is the kingdom of bricks - the best looking on the planet, great selection of shapes, frequently manually made and also cheap

Alpujarras is almost 1000 m elevation, so having some insulation could help.
Bricks can be laid on lime mortar.
Bricks can be laid to create Mudejar patterns - the part of the wall where the concrete frame is, can be plastered. Since they are small, it will be more expensive to lay them.

How thick are the concrete columns?

Rémi,

In this case I would recommend to build a tried out 150 mm BBR in the kitchen area. You will gain some experience in designing and building and then you will see if it improves your life and if it does you will have self-confidence to pursue more complex projects.

Hi Remy,

I'm glad you have accomplished roof insulation.

According to your calculations the average heat loss should be 7.9 kW. Assuming that your kitchen heater will only handle half of the house you are looking at 4 kW heater which would be approximately 200 mm BBR with ISA of 9.4 m2.

If you put the firebox at 30 cm height and the firebox would be also 60 cm tall and rather tight in the bell you could start counting ISA at 0.9 m height. The internal walls would be 95x55 cm to surround the firebox of 90x50 footprint.
The walls at this perimeter would be 3 m tall, so:
0.3 + 0.6 + 3 + 0.13 (bell ceiling) would give you totąl height of around 4 m so it would protrude 1.3 m into the bedroom.
The first 30 cm of the pedestal would be wider and could be beautifully finished with a cornice. The next 60 cm could be built with full brick width (25 cm for Italy). This part of the bell would not participate in ISA and would provide additional support for the tall bell. Also it could provide a base for the reinforcing buttresses (if used) in the wall of the bell.
The actual bell would be half a brick wide (12 cm).

For such a tall and thin structure in a seismic zone I would think about reinforcing it vertically. by using prestressed 10 mm bars in the corners (holes drilled in the brick first). If not then I would definitely build buttresses (they would look great too).

Tall heaters are/were being built in Russia.
For batch box rocket it would be rather a new territory but at the same time you would create a reference to which all would refer. In most cases people would just build two separate heaters, but the tall heater is intriguing and at the same time uses less materials, labor and maintenance than two heaters.

John C Daley wrote:I wonder if instead of scraping out the mortar of each block and relaceing it will a barrier, would something injected into the block itself work?

I have researched it a bit before. Using insulation material in a standard block cavities is almost worthless due to great amount of thermal bridges. 8" block without insulation has R value of 2.0 and with filled cavities around 3.5.