I love Big Bill the clay oven. However, being an engineer, pretty much as soon as Big Bill was built, I had a list of things I’d do differently if we were ever to build another clay oven. (Read how we built him here.)
I thought I’d share the lessons I learned with you regarding the design and building aspects. If you are reading this, I hope you understand my terminologies. If you have any questions at the end, please do leave a comment 🙂
If I were to built another clay oven, I’d have a solid base filled with landfill and dirt, rather than Big Bill’s fancy welded metal support with a concrete slab on top. (The bricks you can see in the top photo is completely aesthetic and serves no structural purpose. You can see the welded structure here.) It IS nice having the room for wood storage underneath Big Bill, but on hind sight I don’t think it’s really worth the extra difficulty in building a base. Plus we learnt that concrete is not a good insulator, and what can beat a solid base in terms of insulation?! (We tacted industrial grade foam insulation to the underside of our concrete slab after finding out too much heat is being lost through the base. Luckily the foam insulation is very cheap.)
I do think it is better to have a chimney for a clay oven. It really does help with getting a happy healthy fire. Building Big Bill involved building a chimney for the first time for us. When we installed the chimney, a friend had already riveted the top on for me to stop rain from getting in. It wasn’t until we had to put sealant between the chimney and the roof that we learned a normal chimney has double layers. Both the chimney top and the sealant should be applied to the outer chute because the inner chute gets too hot and would burn the sealant away. We had to stuff aluminium foil in the joint between the chimney and the roof to act as our sealant. We did also apply some heat proof sealant but it eventually got crispy and crumbled away… luckily the foil seems to do the trick…
(Update: The original chimney top eventually crumbled away from the heat, and you can see the new outer chimney and top here.)
A chimney needs a shutter. A chimney is great for letting the smoke out while the fire is going. However when pizzas are cooking with just kindlings and embers around the the sides of the oven, an open chimney draws too much heat away. We didn’t realise that until our first mini pizza party. We improvised a chimney shutter by bending a piece of aluminium sheet into the curve of Big Bill’s doorway so we could fit it into the doorway and therefore shutting the chimney. It’s a simple solution and it works.
It was also the first time we ever built s roof when we built Big Bill. I’m very glad it has stood through strong gust, pelting rain, and Christchurch earthquakes. There are 2 lessons I learnt. The first one is not to put any post too close the the chimney. The second one is to put on the sloping beams first, followed by the horizontal beams because those are the ones you nail the corrugated roof to.
I hope if you are building a clay oven, you can learn from our silly but thankfully harmless mistakes… 🙂 Have fun!