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Post by curlygirl on Sept 13, 2016 20:26:48 GMT
Hi All,
Been reading this forum for years in the hope of building my own clay oven. This year I made it my summer project when weather allowed (I'm in rainy Northern Ireland!)
My husband and I have never laid a brick before but now we have dug foundation, poured concrete, built block work plinth and work tops and a brick BBQ. We have the first layer of sand / clay mix on a 80cm sand dome and the dome scooped out. We are very proud of the brick arch and chimney - I have learned though that rendering block work is not as easy as it looks on YouTube!!
I think I know what I'm doing with the insulation layer, but I really don't want to put a roof over the top :0(
Was thinking of concrete render? Is that ridiculous? Anyone else done it? Will it crack? Does the clay need to breathe? Any ideas welcome.
Thanks x
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Post by oblertone on Sept 13, 2016 23:47:31 GMT
I can't see the problem with render over clay, as long as you insulate the clay dome with say a layer of blanket, or vermicrete, or something otherwise it'll just become a great big heat sink. You also need something to prevent water ingress down the flue and via the doorway. Regular use will also help as any dry object in a damp climate will attract water; while my oven is waterproof, I do use a patio table cover throughout the Rainey months.
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Post by chas on Sept 14, 2016 7:17:27 GMT
Hi All, Been reading this forum for years in the hope of building my own clay oven. This year I made it my summer project when weather allowed (I'm in rainy Northern Ireland!) My husband and I have never laid a brick before but now we have dug foundation, poured concrete, built block work plinth and work tops and a brick BBQ. We have the first layer of sand / clay mix on a 80cm sand dome and the dome scooped out. We are very proud of the brick arch and chimney - I have learned though that rendering block work is not as easy as it looks on YouTube!! I think I know what I'm doing with the insulation layer, but I really don't want to put a roof over the top :0( Was thinking of concrete render? Is that ridiculous? Anyone else done it? Will it crack? Does the clay need to breathe? Any ideas welcome. Thanks x All as per Oblertone, and if your experience with rendering the blockwork makes tackling the dome daunting, then maybe do as I did (no plasterer, me) and use a small rounded pointing trowel rather than a full-size plastering one, and spread K-Rend like icing a cake. Works well- take a look at my insulation link below. Chas |
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Post by curlygirl on Sept 14, 2016 14:58:14 GMT
Hi Chas, thanks for reply. Had a look at your build - looking great :0) I'm at the builders yard as we speak buying vermiculite for the insulation layer - the sun is shining here so making the most of it!
I've had a few fires and a few hairline cracks (now filled) in the clay/ sand layer. It all sounds hard and looks dry (apart from a couple of inches round the bottom. Do you think it would be OK to put vermicucrete insulation layer on today?
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Post by curlygirl on Sept 14, 2016 15:03:24 GMT
Had a look at the k rend while I was at the builders merchant - looks like the job for me :0) thanks for the heads up!
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Post by curlygirl on Sept 14, 2016 15:05:56 GMT
I can't see the problem with render over clay, as long as you insulate the clay dome with say a layer of blanket, or vermicrete, or something otherwise it'll just become a great big heat sink. You also need something to prevent water ingress down the flue and via the doorway. Regular use will also help as any dry object in a damp climate will attract water; while my oven is waterproof, I do use a patio table cover throughout the Rainey months. My flue has a wee removable chimney pot thing on it which should keep the rain out. I'll have to have a think about a door! |
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Post by curlygirl on Sept 14, 2016 18:12:44 GMT
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Post by curlygirl on Sept 14, 2016 18:14:59 GMT
Few wee pics of my build so far! Stuck on a thin layer of vermicucrete tonight and if the weather holds I might get another one on tomorrow - anyone any idea how long it takes to dry? That layer is 1-2 inches thick.
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Post by downunderdave on Sept 14, 2016 21:21:11 GMT
Around a third of the volume of vermicrete is water and that needs to be eliminated for the vermicrete layer to become insulative. In addition the clay also needs to have the water in it eliminated slowly to prevent cracking. In normal conditions clay takes around a week per inch of thickness to dry before being safe to fire without the risk of steam spalling. It may look perfectly dry on the outer surfaces but will be still damp in the middle. If you have a temp gun do not exceed 200 C on any part of the inside of the dome until it's dry. You should be able to feel the outside of the vermicrete damp if you hold your hand against it. Also try throwing some sheet plastic over the dome when firing to see if water is condensing on the under side. Try to avoid direct flame impingement onto the dome. This is quite difficult with a wood fire so brickettes or charcoal are a better option. Tea light candles are a joke. Think about the total energy they can produce which is relative to their weight (virtually nothing) I'd say you'd need to burn around 20 kg of brickettes with some wood to keep them alight (damp ovens are hard to light and keep a fire going). Sun and wind will help too if you can arrange that, prayer occasionally works.
Just looked at your pics again, Be really careful what you burn in your oven, that timber looks like treated stuff to me. If you are not sure either call the supplier to find out, or if still in doubt don't burn it. Most treated timber is quite toxic if burned and decking timber is usually always treated.
Also looking at the pics of the stand looks like the expanding oven floor bricks may force out your skinny concrete blocks of the stand. Are they tied together with any steel reinforcement or is the bond relying on the mortar joins? Time will tell I guess.
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Post by curlygirl on Sept 15, 2016 21:55:44 GMT
No, not tied together, but there is wiggle room with the oven floor bricks so I'm not all that worried. Think we probably went too hot too fast, but hey, I'm impatient!!! Only tiny hairline cracks which are all fixed and refired now :0)
Yes, I'll have to order a supply of hardwood when I start cooking!
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Post by curlygirl on Sept 18, 2016 13:34:51 GMT
Ok, so I've been reading up about oven door. My thinking is some sort of insulating board sandwiched between aluminium (inside) and nice hard wood with handle on outside? Anyone know how to cover the edges round the outside of the sandwich or have better idea for an insulating door?
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Post by oblertone on Sept 19, 2016 10:10:28 GMT
You can seal the rim of your door using stove rope fixed around the edge for a close fitting door, however I'm not sure you'll need a metal inner face as vermiculite board is fairly resilient. I had a fabricator mark up a shallow dish to my template then glued a piece of vermiculite board inside with silicone, some cheap Aga Handles fron ebay and a short Temperature probe work well.   Stove rope and vermiculite board are available from any wood burning stove installer. fwiw: my door doesn't seal, this allows a little air ingress to keep embers burning all night, which in my case is a good thing as my dome isn't that well insulated. A close fitting door will kill the fire which is ok if you've got the insulation correct. |
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Post by curlygirl on Oct 19, 2016 18:00:57 GMT
3 dry days forecast for our part of Northern Ireland! K-Rend on today :0)  Now if only I could find a reliable plasterer before winter sets in! |
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