I want to build a fireplace under an outdoor shed.
The goal is both open fire for Dutch Oven, cast iron kettle cooking and or bbq nights, you know, the good stuff.
On the end of the existing open shed, no walls just over roofed, this fire place is about to emerge.
The idea is to make a round-ish cob wall, place a roof with overhang on the wall and build a chimney on top of the roof. (Haven’t got a clue on the chimney construction yet, ideas are welcome)
Foundation is layed by some urbanite (smashed bricks) covered with cob.
Since the height of the wall is going to be close to 2.5 meters, I m going to need a fair amount of cob.
Reducing the total amount by adding bottles, cans or bricks in the wall is very tempting.
Since the cobwall is esentially a fireplace, pretty big temperature changes are to be expected.
Adding different materials in this wall, all having their own expansion/ shrinking rates concerns me slightly.
Especially given the fact that the wall is loadbarying for the roofstructure as well as a fair mass itself, I don’t want the risk of the walls falling down due to big cracks.
Hurting my toes or worse, spoiling my meal.
I can imagine that the base of the fireplace up to say 1 meter, takes the biggest temperature swings and therefore should be 100% cob. Above that I would love to use bottles and cans, even if its just for the beauty of the end result.
Hope anyone has some thoughts about this?
Thanks in advance and love to hear from you guys and girls.
you can bury all sorts of waste into your cob walls to take up room as long as it won't decompose or lose its shape over time. My first house I buried a broken toaster and waffle iron in the walls. extra urbanite is especially helpful for taking up room in cob walls.
For your chimney I would just find used 8-10" single wall chimney pipe and use it as a form for a cob chimney. You can get it set in place, then just cob around it.
A 2.5M wall is not too high for cob, just do it in layers.
I encourage people to install steel posts to hold the roof prior to cob construction, its gives shelter to
work under [ rain or sun], catches water you can use during building and gives you something to work on whilst waiting for the cob to dry.
Think about using different materials at the immeadiate fire spot, IE Steel plate, firebricks.
Also think of a Rumsford shaped firebox to maximise your output.
Another concept is to look at Rocket stoves / ovens.
I have buried many bottles in walls, I have a network of collectors.
John Daley Bendigo, Australia
The Enemy of progress is the hope of a perfect plan
posted 4 months ago
Dear Daniel and John (and other permies)
Thanks for the reply, I have checked out the Rumsfort fire box but that doesn’t cut it for me.
The cast iron kettle is 40 cm in diameter and the grill grid is 120 cm x 60 cm. So the shallow fire box has to be at least 60 cm deep, inner size.
As you can see on the pictures, I have started the first batch of cob on top of the urbanite. I might decide to put some more cob on the wooden deck to ingrease the size of the of the actual pit, inner size.
That aside, my main concern stil is, the different expansion/ shrinking rates of the different materials I want to use in the cob wall.
Since glass and cob are both made of sand I expect not too much difference in those but still.
Daniel Ray, what a beautifull kitchen you guys made, big up!
Bit bigger of a project I have started but who knows in the future I might be able to pull something off like that.
Question, is the firebox below just heating the oven by radiation or are the fumes passing through the oven compartment?
I have made a temporary roof out of plastic because I ‘m not sure about the roof yet. I might opt for extending the current shelter roof.
I would much rather build it completely out of cob, chimney and all.
Hoping to seal the outside with boiled line sead oil for weather protection.
Given the fact it tends to rain quite a bit in the Netherlands that might be a bold or plain stupid choice.
It would look awesome though, even if its just for three years.
Ill udate when I’ve got some work done.
Pics are not spectaculair yet.
Thanks in advance.
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