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Post by theboss on Jun 20, 2019 18:08:12 GMT
Just started my first build today. Halfway though building the plinth, from block work, which I plan to fill with hardcore, rubble and topsoil (currently digging out for a patio too) and will top the last 200mm with glass bottles and sand. Then top with storage heater bricks for my oven floor.
Am I on the right track? Or do I need to use more insulation, or more than one layer of bottles?
Thanks in advance
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Post by devontiger on Jun 20, 2019 20:22:57 GMT
Well done boss. But to help post up some pictures so we can see how you are doing. Then we can criticise you better.
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Post by downunderdave on Jun 20, 2019 23:27:16 GMT
Just started my first build today. Halfway though building the plinth, from block work, which I plan to fill with hardcore, rubble and topsoil (currently digging out for a patio too) and will top the last 200mm with glass bottles and sand. Then top with storage heater bricks for my oven floor. Am I on the right track? Or do I need to use more insulation, or more than one layer of bottles? Thanks in advance You can do a lot better by replacing the sand with either perlite or vermiculite. The standard method is to mix the perlite or vermiculite 5:1 with cement and create a 100 mm slab by mixing 3 parts water for every 10 parts vermiculite. Dry vermiculite or perlite around the bottles should also work ok and be quicker and cheaper.
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Post by theboss on Jun 21, 2019 5:30:03 GMT
Thanks downunderdave So my top 100mm should be a wet mix, and then lay my heater bricks directly on top?
I have the vermiculite and was going to use as the insulating layer mixed with clay for the dome
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Post by oblertone on Jun 21, 2019 19:02:23 GMT
Yes, but rather than encase a wet mix straight away you'd be better served either letting it dry out, or using a dry mix to start with.
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Post by lc on Jul 1, 2019 17:07:22 GMT
Hi, Sorry to thread jack.
I have my base down with some council pavers on top at my desired size. I just don't know what to do next, i was going to create a 3" concrete slab on top then put fire bricks on top but i think this is wrong now ? Am i better to create a "vermiculite 5:1 with cement and create a 100 mm slab by mixing 3 parts water for every 10 parts vermiculite" slab then build my oven base on top of this then build the rest on top of that ?
Also have a deadline of getting it finished and ready for bank holiday weekend in August (is this even possible?)
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Post by oblertone on Jul 2, 2019 8:16:06 GMT
Yes, it's possible (se my build thread below), you might not have the finished article but a working oven is doable.
You need to insulate under the firebrick base otherwise it just becomes a heat sink, I used vermiculite board but other 'dry' alternatives are available, you just need to ensure they stay dry. Using a vermicrete base (proportions as you describe) will mean an extended drying out time as you really don't want to enclose a wet base.
In all of this don't forget where your base needs to be height-wise; you should aim for the cooking floor to be at the elbow level of the main user for ease of use.
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Post by lc on Jul 2, 2019 13:10:49 GMT
Hi, thanks for the reply.
I have been thinking about the insulation base on top of my slabs and would using 4” thermolite blocks laid sideways with 50mm vermiculite board on top followed by the fire bricks surpass ? Just worried about the pavers cracking with heat.
Still tempted to pour a 1” concrete slab to tie them together then the above on top.
It would be solid if nothing else.... from reading I know i can’t rush the drying period so would sooner go dry route for the and pay extra and be able to crack on with the actual build quicker.
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Post by oblertone on Jul 2, 2019 19:26:07 GMT
I think that would be more than adequate; I used 25mm of Vermiculite board direct into a steel pan then storage heater blocks on top. The underside of the pan reaches about 70c during use so your plan would be considerably less; go for it.
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Post by theboss on Jul 4, 2019 18:33:48 GMT
Yes, but rather than encase a wet mix straight away you'd be better served either letting it dry out, or using a dry mix to start with. What should the consistency of the vermicrete be like? I’ve mixed 5:1 vermiculite to cement and 3 parts water for every 10 vermiculite, and it was very dry and like granola. I’ve done a 50mm layer and left it overnight and it’s pretty flaky today with no smooth finish. Does this sound right? If so I’ll get another 50mm on and leave to go off for a couple of weeks. I plan to bed my storage heater bricks on a bed of 10-15mm dry mix sand cement 4:1 as the bricks I’ve salvaged are different depths.
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Post by doggit on Aug 5, 2019 22:47:44 GMT
Sorry guys, I'm going to have to jack the thread because I can't find out how to start one, but it's all along the same lines.
So, not a large oven. Building 2 side plinths with concrete blocks, then set in a 50mm reinforced slab, followed by 25 vermiculite board, and I was going to use storage heater blocks for the base, but I was wondering whether I could put on an inch of cement fondu mix to give a smoother base. After that, I was going to build the dome with storage heater bricks, then a 20mm vermiculute blanket, and then finish off with any cement fondu I've got left - could I get away with 1 bag, or do I need 2.
Any help advice or criticism greatly appreciated. Cheers Guys.
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Post by oblertone on Aug 6, 2019 7:55:14 GMT
How big is a bag ?
As to the base construction, the vermiculite board will give you a perfectly flat base on which to place your heater blocks, if you think you need more then put it underneath the board not on top.
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Post by doggit on Aug 9, 2019 0:50:15 GMT
The ciment fondu bags are 25kg, and looking at their site, you use 40ltrs sand and 10lts of water to each bag, and that makes your mortar mix, or you can knock up a concrete mix using aggregate. I was thinking I might put 25mm over the heater blocks to give a nice smooth surface.
I've built the base, and just laid the first part of the slab using concrete and ballast, and when the storm passes, I can then put on the 25mm vermiculite board, and then start laying the heater blocks. I've picked up some 13mm ceramic blanket (over 14M of it if anyone wants the leftovers), so 3 layers will get it well insulated, and then use a cement render on top of that.
I think I've done my back in, but it's been a good couple of days. The ciment fondu will take a few days to arrive, so I should have recovered by then
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Post by james9 on Aug 10, 2019 9:49:40 GMT
My gut feel is to more than double your insulation layers. I used 50mm of Calcium Silicate board on a concrete base and with hindsight would recommend 100mm and also its really important to keep it dry otherwise heat conducts through wet board. The problem is if the concrete base heats up and I've recorded temperatures over 80c then the concrete and rebar expands causing the base and dome render to crack. Ceramic blanket is surprising difficult to handle and whilst 13mm will be easier, I recommend min 50mm all over with another 50mm over the top of parts of the dome. I'd go for 100-150mm of vermicrete over the blanket. This might seem over the top but really works, the top of the dome can reach over 700c with the outer dome 25-30c. The critical thing is getting the base insulation right.
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