5. The Oven Entrance and Chimney

The oven layer is complete!

Just a dome-shaped sculpture without the entrance and chimney.

You have completed your first layer and now you need to build a nice entrance at the front of it in order to get food in an out (unless you leave it as a dome shaped sculpture!). At this stage we will also be removing the sand former and building a chimney.

You should have left the oven layer to dry for at least 4 hours before you attempt to cut the oven door but don’t leave it so long that the clay-sand mixture dries too hard or you will find it tricky to cut.

The dimensions of the entrance are dependant on the dimensions of your oven. Generally though, you don’t want it so big that it effects the heat retaining potential of your oven nor too small so you can’t get anything bigger than a tiny pizza through it.  In the end I chose the width of my door based upon the width of a standard roasting tray and, as it happens, the width of the bakers peel I had bought.  Don’t worry too much about the height at the moment because you will probably adjust that later on once you have fired it.

The oven entrance removed revealing the internal sand former

The oven entrance removed revealing the internal sand former

Roughly mark the width and curve of your oven entrance and then, using nothing other than a carving knife, slowly cut it out.  It will probably come away in large chunks – a very satisfying experience!

This is the moment of truth! Get yourself a bucket and start to excavate the sand from within the oven layer. Don’t forget to keep the sand for later clay-sand layers. Hopefully you will be able to excavate the sand until you reach the newspaper layer on the inside of your oven without the dome collapsing.  Take it nice n slow but I’m sure you’ll be absolutely fine.  Remove as much newspaper as you can but don’t worry too much because it’ll burn off anyway the first time you fire the oven.

Firing the oven

Kindling burning in the entrance to the oven.

Kindling burning in the entrance to the oven.

Next you need to dry your oven layer.  If you are lucky enough it will dry nicely over a few days in direct sun. However you should also fire the oven at least once to help the drying process but also to check the entrance is high enough to allow smoke to escape (see below).

The method for firing the oven is quite simple but do bear in mind that at this stage the oven will be rather damp and does not have a chimney so you might find it takes a little bit of perseverance to get the fire going. This is how I do it:

  1. Prepare some nice “pencils” of kindling.
  2. Scrunch up five or six pages of newspaper into balls and form into a rough pyramid inside but near the entrance to your oven.
  3. Build up kindling around the newspaper as if building a wigwam.
  4. Light the paper and hopefully the kindling will soon ignite.
  5. Watch the fire closely and keep slowly adding more and more kindling until it starts to burn well.
  6. At this point, using a spade, metal rake or even a bakers peel, slowly push the fire back a little into the oven.  Don’t push it too far because it is likely to go out.
  7. Add more wood and when it is burning fiercely move it back some more.  Eventually you want the fire to be burning in the centre-back part of the oven.
Fire blazing with dry patches appearing on the outside of the oven.

Fire blazing. Note dry patches appearing on the outside of the oven.

A couple of tips here.  Firstly, take it slowly. If you try to move things along too quickly you are likely to extinguish the fire.  If it looks like it is going out, screw-up a few balls of newspaper and throw them in. This is usually enough to re-kindle the blaze.  Secondly don’t use large chunks of wood  – smaller pieces burn better.

At this point you can modify the height of the oven entrance if you need to.  Look carefully at how the smoke is moving.  If it is “pooling” inside the top of the oven you need to cut your entrance higher to allow the smoke to escape.

As the oven dries it will steam and might produce a few cracks.  Don’t panic!  Fill in any cracks with spare sand-clay mixture before you move on.

Building the Brick Arch

Now the oven layer is dry you can build the extension to the entrance.  Extending the oven entrance with bricks not only looks nice but it also protects the entrance from knocks.  

Simply build a sand former in the newly cut arch of your oven, extending forwards about one brick length. Place a brick either side of the former on the top of the plinth using some of the sand-clay mix as mortar to hold them in place.  Gradually build up the archway around the former using more of the “mortar” mix between bricks.  You might have to use quite a lot of “mortar” in order to produce the correct curve for the arch (as you can see in my photographs below).  The last brick should form the keystone of the arch.  Leave the “mortar” to dry a little then remove the sand former. Hey presto – a perfect arch!

The Chimney

You need to cut a circular hole in the top of your oven just behind the brick arch entrance.  I sketched a rough circle on the top with a pencil then drilled holes around the circumference in order to help with removal of the now solid “cement”.  Just tidy the edges up a little with a knife then build-up a small 20cm chimney around the hole using more sand-clay mixture.  Finally, close any gaps between the brick arch, the oven entrance and the chimney using the remaining sand-clay mixture. 

Entrance and Chimney done!  Leave it to dry before we move onto the next stage – the insulation layer.

Brick arch and chimney complete.

Brick arch and chimney complete.

The brick arch and chimney from the front.

The brick arch and chimney from the front.


140 thoughts on “5. The Oven Entrance and Chimney

  1. These look great getting stuff together building plinth from sleepers very soon , trying to find clay supplier near York? Any ideas? Thinking using a foot long clay drainage pipe as chimney will it do the job ?

  2. Hi there
    spring time and i noticed a number of cracks on the surface of my oven. Usually i mix sand/clay and fill in the cracks but once it dries up, the cracks reappear. Would it be better to use pure clay, and not a sand mix? Oh,one other thing…i tried to make a chimney last year and it was a disaster! I used slate for my plinth so i have an uneven surface and i found it quite difficult to build the chimnet. So i just went with a hole for the entrance. But i’m finding that my fires seem to snuff out rather easily. Is it possible that i’m snuffing it out by not letting the smoke escape? Could i drill a hole at the top and build a make shift chimney?


    • Hi Peter. Clay and sand is the best mix to use. Clay will just contact more when dry and crack even worse.

      I’m not clear what you mean re. your chimney. Can you send me a photo (simon.brookes@gmail.com).


      • I can send a pic later today. And I guess I should clarify what I first said. I cut the hole, dug out the sand, but could not make the entrance/chimney. I have a slate plinth, which is really cool but i’s uneven, that could be the problem. So what I have is the oven, and a hole on one side that I cut out. No brick entrance, no chimney. I think as a result, my fire snuffs out often because I’m constantly having to work the fire, and the oven doesn’t get very hot. The fire is never roaring, if you know what I mean. It’s good to start but as soon as I try to push it into the oven, it starts to die out.

        I was thinking I would bore a hole in the top and build a chimney with some leftover clay, hopefully this won’t destroy it. and I could try again to build the entrance, but it was an exercise in futility, I’m glad I didn’t take a picture!

      • Thanks Peter. I understand now. Your oven won’t fire properly until you have the chimney in place. Just cut a circular hole behind the entrance. This allows the hot air to escape (with exhaust smoke) which will cause more air to be sucked in from the entrance. As a result you’ll get a very hot oven. The chimney should be near the front of the oven, not the back, so that the air rolls around the back, then top of the oven. This also generates lots more heat.

        If your oven is hard dry, use a drill and drill lots of holes, in a circular pattern, in order to create the larger chimney hole.

        Have fun!


      • Thanks Simon. I’ll give this a try, and i may send you a picture of the oven later today


      • Hi again Simon. Still not much luck with my oven staying fired. Initially, the fire is roaring quite well but eventually it just starts to smolder and then next thing i know i’m fighting to keep it going. Could be that i’m using pieces of wood that are too thick? The small pieces seem to burn well, it’s when i start with bigger pieces it starts to die out. another thing, i built a chimney at the top of the oven. I can see the smoke billowing out of it, but it also continues to billow out of the actual entrance of the oven. Apart from re-building (again) I’m not sure what the solution is to this.

      • HI Peter. Are you building the fire at the front and getting it going well before you begin to slowly push it towards the back? What size chunks are you adding? Can you take me a phew photos? (simon.brookes@gmail.com).


      • HI Simon, sorry, but i can’t seem to reply to your most recent post, so i need to keep going back to an older one. I’m going to send you some pics of my oven, hopefully you can provide some tips as to why it’s snuffing out. Perhaps it’s just not high enough. keep in mind, i didn’t make the oven exactly as you showed it becuase i didn’t have the material for the plinth. So it’s a bit unorthadox, i’m really hoping I (or you) can solve the riddle as to why it keeps snuffing itself out!

  3. Hi Simon
    I’ve just fired up my first layer and all looking good with no cracks…touch wood! However I have noticed a pooling of smoke about half way up the oven…my opening is above this (more than half way up). Is this normal or should I make the entrance higher?
    Thanks Billy

  4. Hi Simon
    I have got as far as cutting the entrance, the oven is still a bit wet so I’m going to leave it for another day before removing the sand. I was wondering about using plasterers expanded galvanised metal scrim to form a tube for the chimney then bond the bricks to it what, do you think?
    regards Jeff

  5. Hii Simon

    Nice and informative site you got there.

    I have being longing to buy earth oven for 2 years now but haven’t have the time to do it.. or material to do it.
    I am at Downham , uk, i can’t really locate a source of clay for my oven, that’s the problem. there is a company offer clay for sale, rather near my place, but after looking at the photo of the clay, it is grayish.. that’s scares me, looks like dirty clay..


    take a look and comment pls.

    another question, is it possible to buy inner core with fire cement + clay + sand ?
    i heard cement + clay is very strong.. maybe with fire cement it can handles accidental poking of firewood ?


  6. my oven got another crack in it, just like last year. Right above the door entrance, and i think it’s right through. I’m not building over again! If I put two more layers on, plus my chimney and entrance, perhaps it’ll be ok? As long as i can use the oven i’m not overly concerned.

  7. Simon, exactly how do you “build” the chimney, just with your hands? I just finished the first layer, and tomorrow i’ll be cutting the door out and removing the sand. I think I’ll be ok with making the entrance but am hesitant about the chimney. Also you say cut a circular hole but your chimney looks rectangular. I’m thinking it’s going to be rather tough to make a shape like that out of the clay.

    Once again, thanks for all the help.

    • HI Peter

      yes, with your hands. Cut a hole in the top, just behind the entrance and brick arch (it may intersect with the entrance). It doesn’t have to be perfectly circular of course. I’d aim for something between 20-25 cm diameter. Once you have cut the hole, start to build up walls around it using clay:sand “bricks”, as you did the layer 1. Make sure you make the chimney thick because otherwise it’ll be really fragile. I normally overlap it onto the back of the brick arch. Also, build it tall enough to accommodate (i.e stick up above) the next two layers of oven (the insulation layer and the final layer).

      Here’s a cpl of sketches which might help:

  8. Hi Simon,
    We’ve got this far on our oven build, but the day after we finished the arch and chimney we had a bit of storm and it’s got a bit wet and cracks are forming – How worried should we be about this? Is it ok get it to dry out and then we can patch with more clay mixture?

  9. Hi Simon
    Is there any problem using a galvanised metal flue pipe from a Boiler? My thinking is position the pipe and use it as a form and build clay round it but leave the pipe in permanent?


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