starting my clay oven.....................or maybe not.

[Mickey-t]

Hello everyone.

I had been planning to build a lo-tech clay oven, but after studying this forim, I am coming around to the idea of a more permanent brick oven.

The thing that set the ball rolling for me was a TV programme that showed the construction of this oven, and I thought "I can do that"

Here's the link: au.video.yahoo.com/watch/2972929/8334268

I'd be very interested to hear if anybody else has built this type of oven, and whether they were happy with the outcome. I am a little worried, as the base is constucted with clay pavers rather than fire bricks. I have held a blowtorch to a clay paver for a good 20 minutes, and there was no sign of stress, or any "spitting".

I am almost at the end of constructing my base, so any feedback would be most welcome.

Thanks

Mike

[dmun]

Re: starting my clay oven.....................or maybe not.

Ovens have been built successfully with plain clay bricks, the harder the better. Don't neglect to insulate: Once the floor's down, that's hard to retrofit.

[Ken524]

Re: starting my clay oven.....................or maybe not.

That guy was showing some sort of insulating material in the first 2 stands he displayed.

On the concrete block stand he used crushed granite and sand under his floor . That doesn't sound like much of an insulator. Put some FB board or Vermic/cement under that and I think it would be really slick!

[Johnny the oven man]

Re: starting my clay oven.....................or maybe not.

OK, that oven build was on Better Homes and Gardens in OZ. For all the build info, it was by Alan Watt. Check him out on Wood Fired Oven Workshops very knowledgable gent, buys most refractories off me. Yes should be insulated under base, but he uses the base as a heat bank.

[Mickey-t]

Re: starting my clay oven.....................or maybe not.

Thanks for the replies folks.

So, Ken, you reckon granite/sand is no good under the hearth?

BTW, what is FB board? Pardon my ignorance, but I'm very new to this.

[dmun]

Re: starting my clay oven.....................or maybe not.

BTW, what is FB board? Pardon my ignorance, but I'm very new to this.

Forno Bravo sells a two inch thick calcium silicate board, which is an industrial refractory insulator. If it's impractical to get it from Forno Bravo, then a local refractory dealer should have something comparable.

Any plan to use a "heat bank" under the oven floor is doomed to failure, unless you have unlimited time and wood.

Insulate! Insulate! Insulate!

[Mickey-t]

Re: starting my clay oven.....................or maybe not.

Insulate! Insulate! Insulate!

Thanks for the advice mate.

Would a mixture of perlite/vermiculite, with sand and cement be any better than the crushed granite?

[Frances]

Re: starting my clay oven.....................or maybe not.

Yes it would, much better - only leave out the sand.

[Mickey-t]

Re: starting my clay oven.....................or maybe not.

I would still need a 20mm layer of sand above the perlite/cement mixture though as a bed for the clay pavers/bricks. Would this still be OK?

Also, how thick should the perlite/cement layer be? I'd be guessing at about 75mm. Sound OK?

BTW, thanks for your help everyone. I am hopefully going to install the base over the weekend.

Mike

[dmun]

Re: starting my clay oven.....................or maybe not.

Also, how thick should the perlite/cement layer be? I'd be guessing at about 75mm. Sound OK?

The recommendation for vermiculite concrete under the floor is 4 inches or 102 mm.

[Wiley]

Re: starting my clay oven.....................or maybe not.

"I would still need a 20mm layer of sand above the perlite/cement mixture though as a bed for the clay pavers/bricks. Would this still be OK?"

I would suggest that you reduce this layer to 6mm. I know it seems counter intuitive but vermiculite/cement (commonly referred to as vermicrete on this forum) is more than adequate to support the clay pavers/bricks. The layer of sand would only be for leveling the pavers and one if one follows the "directions" one would mix this sand with fireclay.

I mixed my vermicrete using a 10 to 1 mix/ratio of vermiculite to cement and it is plenty strong. And more is better regarding thickness, if you could accommodate the extra thickness 15 cm is better than the recommended 10cm (OK for the purists 102 mm); the thing is more insulation is better and unless you are going to be baking multiple batches of bread you don't really need the extra heat sink.

But Hey, it's your oven do as you want. The forum is full of good advice much of it learned by doing and as a result finding out what worked and what didn't and what could have been done differently to make a better end product. One of the mantras here is: insulate, insulate, insulate, if you cannot afford high tech, that's fine then use low tech and just use more of it.

And for me one of the great things about this forum is the freedom to ask about weird building ideas and not be flamed for suggesting something that might be heretic. And also the maturity of the members who say "I did this and would advise anyone else thing of doing the same thing to perhaps think again 'cause it didn't work for me."

Wiley

[Mickey-t]

Re: starting my clay oven.....................or maybe not.

That's it.

I think Wiley has hit the nail on the head for me.

I have about 6" to build up to my floor level, so I will go for the vermicrete, with a minimal layer of brickies sand just to level/bed the pavers in.

Your help and advice is very much appreciated. THANKS!

[Mercury70]

Re: starting my clay oven.....................or maybe not.

Mickey-t,

I have just finished building the "low tech" clay oven from "better homes and gardens "and it works just fine . Cooks pizza in a couple of minutes, and holds the heat well.

I did modify the design slightly as follows;


I didn't use the granite mix on the base , but used the perlite mix for insulating properties.


When making the clay dome I added extra "Sisal" to the mix to assist in the prevention of cracking, as I have a friend who had built one using the same design and he had some cracks in his dome.- Seems to have worked as their is no cracking at all in my oven

I wrapped the clay dome with some industrial type fibre glass, covered this in chicken wire and then added the perlite insulating layer. By the way the addition of the clay to the perlite mix helps to make it "sticky" and a lot easier to work with than just cement , so don't be too concerned when laying the base that the perlite mix will be difficult to work with. The extra cost of the insulation is worth it.


I then made up some waterproof render mix and finished the outside. This is not in the design but it makes the oven weather proof.

The other piece of advice is to follow the instructions on curing the oven. Being of clay design their is plenty of water to be driven out so take it slowly.

Feel free to ask any other questions.

[Mickey-t]

Re: starting my clay oven.....................or maybe not.

That's great to hear somebody has succesfully built this oven.

I have got the base down (100mm layer of perlite/cement), and I have bought a metre of sisal rope, which I will use the whole amount.

Could I ask you where you sourced your clay? This is the only item I am struggling to find. I will need to use a powdered clay, as there is no natural clay in Perth.............only sand..............everywhere.

I was going to ring the brick companies to see if I could get some from them. They must have tonnes of the stuff.

I like the fibreglass/chicken wire idea, I think I will copy you there too.

Thanks for the info mate.

[Mercury70]

Re: starting my clay oven.....................or maybe not.

I live a couple of hours drive away from Sydney, So I was able to get the clay from a pottery supply shop. It is Known as Ball Clay , comes in 25kg bags and cost around $1/Kg. You will need 2 bags and this should give you some left over for any repair jobs eg cracks. I have one crack in the external render around the Flue.I think the reason for this is that I did not put enough fibre glass insulation around the flue.

When doing the clay, try and pick a cool day as it does tend to go off rather quickly.