First post, first clay oven build, first of many q

[jonnygunit]

Hi everyone,

So this is my first post, I love pizza and have decided to build my very own wfo in my garden here in Wales. Originally I set out to build a small standard cob oven using only materials from my garden, with my only real expense being some good quality firebrick for the oven floor. The plan was to use the wine bottle and straw cob methods to insulate the clay dome. However, trawling through the wealth of info on this great forum it is scary how easy it becomes to justify always going that one extra step (Oh go on then just a few more inches internal dome size! Vermicrete instead of the wine bottles you say? Why not!). Expense is my main concern and the one place I will be drawing the line is with using clay over bricks for my domes thermal mass layer. I hope to one day to build a grand all brick Pompeii, but it wont be this summer I'm afraid.

So, with this in mind my first question is this (1) Is it still worth the extra expense of vermicrete insulation if I have already opted to 'bottleneck' the performance of my finished oven by using clay instead of firebricks for the dome? (I'm assuming expensive bricks must do a better job than mud from my garden)

I'm hoping my oven will see action about once a week, mostly for pizza but probably some light bread baking and roasts etc aswell. Im thinking of an internal floor diameter of 26" which I figure will easily cope with a couple pizzas at once and be sufficient for my needs. (2) Based on experience does anyone feel I'm likely to live to regret going so small?

From what I understand I can never have too much insulation, but too much/little thermal mass can be a problem. The firebricks I have sourced are from an old storage heater and, at 45mm thick, I think they are a bit thinner than the bricks people would normally use. (3) Will these bricks provide a sufficient thermal mass layer for the oven needs I have described? (4) How thick should I make my dome's clay thermal mass layer? (I believe this is just clay and sand with no fibres added, please correct me if I'm wrong).

Im really excited to get started with this. Building on my natural stone plinth will begin next time there is a break in the rain!

Thanks for reading and any help would be greatly appreciated,

Jon

[surfingspider]

1. I don't have vermicrete so couldn't tell you how much better it is. I would consider doing upto floor level as good as possible so you can do full brick oven, then top it with a clay oven for the time being. That way in the future you can just knock down the clay and build up from there.

2. I have a 27" oven floor and it is fine. It is a bit two small for 2 pizzas to be moved around easily with a fire in as well but as they only take 3 mins to cook one at a time you can cook 20 an hour in theory which is plenty!

3. I am sure those bricks will be ok. You can always put some more of the clay and sand build mix between your under floor insulation and bricks to increase the thermal mass if you are worried about it.

4. My dome is about 4" thick clay sand mix. I used the width of my fist as a measure. Yes the build mix is just sand and clay in the right proportions. Then a 4" layer of insulation (Clay slip and sawdust). Then a 2" plaster layer of clay, sand and straw (to give tensile strength) plaster layer. Remember all clay from the garden is different. So it is worth doing a few 1 " thick test bricks of different ratios of sand to clay and let them dry out naturally. Pick the one that doesn't shrink to much and doesn't crumble under pressure.

[jonnygunit]

Thanks for the reply. I actually remembered your build thread once I saw you profile pic there. I stumbled across it from someone else's thread who had copied your idea of a brick ring at the base, and I think I might just nick it aswell! How did you come to decide on a 4" initial clay layer? If it was something you read about I dont suppose you can remember where?

[surfingspider]

I followed kiko dezers build your own earth oven book quite closely and can't recommend it enough. That is we're I got the 4" from

[rivergirl]

I wenrt the wine bottle route ( well I had to really !!! ) I laid them on sand bedded them in and continued until I reached the required height) I have a nice big oven plenty of room for roasting pans, and crockpots etc !! after grillstock my sister has now decided she wants one ( at last) so I will be coming back to Wales to help her build it .. she has a nice leafy glade that has a stream running through it that feeds the \Severn so its going to be a fabulous place to build it !!