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Post by gracie on Apr 12, 2016 20:47:37 GMT
Hello all, I am researching my build and I'm pretty sure I'll go for a cob, not least to reduce the build cost. I've seen a few people say they want to rebuild in brick or build a different style next time....so my question is, with full insulation ( blanket/ vermicrete) plus render, how long can I expect my cob oven to last. Is there any advantage to building the dome with fire clay and firebrick grog or stainless steel needles instead of a simple clay sand mix? Would this extend life or improve functionality?
thanks for the inspiration so far!
Gracie
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Post by downunderdave on Apr 12, 2016 21:41:18 GMT
Hello all, I am researching my build and I'm pretty sure I'll go for a cob, not least to reduce the build cost. I've seen a few people say they want to rebuild in brick or build a different style next time....so my question is, with full insulation ( blanket/ vermicrete) plus render, how long can I expect my cob oven to last. Is there any advantage to building the dome with fire clay and firebrick grog or stainless steel needles instead of a simple clay sand mix? Would this extend life or improve functionality? thanks for the inspiration so far! Gracie Combining cob with modern expensive materials like ceramic blanket, vermiculite and stainless steel needles is a poor choice IMO as you will not end up with much saving of expenditure and still have an oven interior that is relatively weak and will abrade easily. An excellent and cost free insulation mix can be obtained using chopped straw bound with just enough clay slip (clay and water slurry) to make it hold together. Do though, go for firebrick for the oven floor if you can afford that. For the temperature range of a WFO there is no advantage to using fireclay or firebrick grog IMO. |
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Post by gracie on Apr 13, 2016 8:53:10 GMT
Thanks Dave,
There is so much information to absorb, so many products mentioned it's hard to make sense of it all to start with. So the cob interior is the weak point as it were, and doesn't benefit from anything fancy over the top. I'm guessing then that a brick dome lasts longer. Could I use a recycled brick for the dome if I use fire brick for the hearth?
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Post by zelige on Apr 13, 2016 17:41:50 GMT
For what it's worth my cob oven is still going strong after 5 years. It's insulated with a mix of clay slurry and perlite (about 2" worth) then a lime render. It was tarped up for 2 years to keep rain off but I've now built a green roof over it.
Adobe structures exist all over the world and last lifetimes albeit with regular maintenance.
Think the most important issue is to waterproof it with roof or tarp. Once that's in place I can't see a rain why you won't have decades of pizzas from it.
Warning - once you've got it done you'll want to build a brick oven!
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Post by gracie on Apr 13, 2016 18:53:39 GMT
Thanks zelige! I'd be happy with 5 years out of it, and I believe your warning !  ? |
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Post by zelige on Apr 13, 2016 19:06:40 GMT
I've almost completed my first brick oven after about 15 years of building cob ovens. Although it's very exciting to move on to the challenge of working with brick, homebrew and cement i think fondly of the beautiful tactile quality of clay - every smudge, smear, scrape on the dome is from my touch. The clay came from a mile away where it had laid in wait for tens of thousands of years to be turned into a fantastically effective oven and man space at the bottom of the garden!
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