Clay oven in Cambridge

[cannyfradock]

Salilah

Love the last pic.....great looking Clay oven and I love the roof.

Couple of points....Is the plastic chimney a temp measure?...hope not. You need something clay or ceramic based for your chimney. On clay ovens I use a thick ceramic flower pot, cut the bottom off and turn it upside down.
If the entrance to your dome is less than 63% of the height of your dome, it may not get the flow of air it needs. This is the "ideal" % but will still work if you're not to far away from this %. The problems you had (as previously mentioned) could have been moisture or not enough heat in the oven. It may take quite a few attempts to start a fire in a new damp oven. Keep persisting. Make sure your kindling is bone dry ans small. Once a little bit of heat is absorbed in the oven the magic of these beauties will start to work and DRAW new air in. This new air will expand when heated and curl over the top of your oven and exit at the top of your entrance. Smoking is normal when firing up but as soon as you get used to the oven this will become minimal.

You haven't mentioned any type of insulation under your hearth. This really helps with keeping the hearth hot. If there is none....don't worry. It means it will just take a little more fuel than normal.

Read this for tips on uploading images.. ukwoodfiredovenforum.proboards.com/index.cgi?board=info

If your clay oven building course was good why not pay him back and put him in our "Clay oven courses" section of the forum.....I have heard of a "Rupert" clay oven builder but not sure from where.

Terry

p.s....sorry for the long post

[salilah]

Thanks Terry!

Re the chimney - we didn't want to leave the plastic - so I guess we need to find something as a replacement. On the course we went on, they only left a hole (large tin can size) and covered it with a tile when they wanted to keep the heat in (!). We have a piece of (I think) land drain (circular inside, hexagonal or octagonal outside) but I thought this would be too heavy to sit on top of the clay without a support?

Entrance - yes we measured, and calculated and it is (or should be) at 63%! I'm hoping it is the damp, and will keep trying - the second fire burned a bit better than the first

Insulation - the course said air was fine - so we hope 2-3" of air gap will work! If not, I might dig another hole and fill it with vermiculite or something (we have a bag)...

Thanks for image hint - will investigate for next post...
cheers!
S

[dougclay]

That's a nice simple roof design. I really wish I'd considered a roof before we built the oven...
What kind of timber is that you used in the frame? Are you going to have a chimney directing the hot smoke away from the roof?

[salilah]

I'll check with OH re the wood - it was stuff we had spare from making a large deck for the little barn a couple of years ago. Very heavy!!

Chimney - now this is where I'm really not sure! How much and how hot is the smoke when operating??? The ovens on the course we did didn't have chimneys - their roof was higher but not much!

There doesn't seem to be that much info about chimneys - any suggestions?
much appreciated
S

This is OH - Roof is basically a 4x2 frame with 9mm OSB screwed on top. Size is 2400x1200mm, with two cross-braces of 4x2. Feels over the top to start but the old tiles on top are incredibly heavy. Next time I would use roofing felt and a lighter frame - less cute but less work.

[dougclay]

How to handle the chimney exhaust is why I'm curious as I have the same dilemma... The chimney does kick out quite some heat, especially during fire up...

[cannyfradock]

It will get extremely hot in the chimney and I've heard of clay pipe cracking due to the heat. My first oven had a flower pot on the top. I took that oven way beyond normal firing temps......and the render cracked, but the flower pot didn't!!!

Not sure on the land drain as the one's I've come across have very thick walls and a small (2") center. I've only built 1 clay oven and I built a brick arch at the front to take the chimney........

Terry

[salilah]

Another question if I may - regarding the final layer!
We did the insulation layer - clay slip with wood shavings - and it is now pretty damp but finished (bad weather - we went off to Turkey instead!)

Final layer - I'm thinking some form of lime render? (and I have a load of little mosaic tiles to make it pretty!!)

I've searched, but most posts on lime are talking about mortar for a pompei?? What sort of mix should we be thinkign about for the outside layer, and how thick?

thanks!
Sali

[bookemdanno]

Hi Hi Hi Salilah!

Try this...
www.stastier.co.uk/nhl/guides/rencob.htm

Hydraulic Limes are breathable, and perfect for Cob Ovens. They can be Limewashed for a traditional method of weatherproofing but this can bleed off during continued heavy rainfall and needs replenishing.
However St.Astier do a range of ready mixed Lime Renders with Integral Waterproofers.

www.stastier.co.uk/nhl/guides/wkgecom.htm

Ecomortar WP seems to be the one! They are extremely helpful and passionate about what they do. Drop them a line, and they'll let you know what and where you can get it.
I'd say there are comparable products elsewhere, but St.Astier have helped me, so i will push their products!

[salilah]

Thanks bookemdanno!
We've got a roof but certainly recently the rain appears to be coming sideways <grin>
Will follow the links
cheers
S

[rivergirl]

Lovely build! I also only had candles going in itfor a week or so then twig fires then I lost patience and built a fire!!

[salilah]

Thanks for your comment Rivergirl!

I must dig out some final pics - the oven is now well-seasoned and runs well
OH had a significant birthday party a few weeks ago, so we used the BBQ (home made sausages and sous-vided chicken and duck) and the oven for pizza - OH's daughter and fiance, with a bit of help, managed to turn out 7 pizzas without relighting (I think, I was doing other stuff!)...

We also use it for bread - I've still not quite got that sorted yet though, we have a lovely door, but it is a bit of a hassle clearing the coals and retaining the heat without burning the loaf at the beginning - think I need more experimenting!

If we've done pizza or bread, we also tend to put dinner in (I've an enamel big dish with lid that fits a chicken or joint with a load of veg) - again varying success with temperature, but usually it works fine (and easy enough to move to the house oven if the temperature has got too low...)

I haven't played with it much this year - fewer loaves as I've been doing paid work, and I've also been playing with the sous-vide for dinners, and tried smoking stuff in the BBQ - must get back to it, especially the bread!

cheers
S

[rivergirl]

Sounds like my first experiments as well and I have only just used it for a pizza ! But this year I have been doing most of my cooking in my primo. Got the bug again when I made a pizza the other week !