low cost wfo build

[kstronach]

hi all,

OK so i have decided that my next project is going to be wood fired oven! after reading through tons of post both on here and over at pizzamaking.com i think what i want to do is an igloo dome oven with a fairly lowish ceiling height for quicker warm up and faster cooking times (hopefully!) originally i liked the barrel vault ovens as it would be a cheaper and easier build however have been put off by some peoples opinions on them and longer heating up times.

OK so heres how i plan to do it hopefully depending on what people think as i have no experience at all when it comes to WFO's!
basically i am looking to keep costs down as much as possible due to my the impending arrival of my first child !! and also the weather over here in England's not great to say the least so probably not get as much usage as i would like! will external temps affect the internal temp at all? would it be possible to use all year round even in freezing conditions? if i get wrapped up!!

i am pretty much going for the forno bravo Pompeii oven shape etc but the catch is instead of the brick dome i am going try to cast the dome around a sand mould out of a castable refractory mix, I'm then going to bed the cast dome atop a course of firebricks or red clay brick upright for the first chain leaving out the inner door at the front so the height of the door would be at about 9 inch ( the top of the upright brick). i am hoping for a ceiling height of around 15 inch? i have been advised this is a good hight for pizza? and oven width of around 36" i will the build a brick outer door with red brick and a chimney out of that as normal. also i could put a thermal blanket over the dome for extra insulation purposes if you think this is necessary then mesh and render over that! i think this oven would be visually appealing with a brick front arch brick chimney and a first course of brick around the dome and the rest painted cement render.

the floor make up would be insulated conc with firebricks bedded on that or maybe a few corderite kiln shelves or i could maybe get hold of some granite but I'm not sure on that and how it performs under heat?

do you think a cast top dome will get hot enough for neo pizza oven temps?? i would love to hear peoples opinions on the cast dome good or bad!!

how is all this sounding am i going along the right lines? any help is appreciated as I'm going to start gathering materials probably in the new year.

sorry its a long post but wanted to try and get enough information across as possible! thanks in advance for any help i look forward to hearing everyones opinions!!

Keith

[UtahBeehiver]

Re: low cost wfo build

Check out "Bookemdanno" on this forum. He is from the UK and can guide you on materials and ideas to help with cost. He just finished his build recently......

[david s]

Re: low cost wfo build

Using castable refractory over a sand form is an easy way to make the dome. Go for a thickness of around 2" and use damp newspaper between the sand and the castable. Mix up small batches at a time until you get the hang of the stuff. It goes off really fast and is expensive, you don't want to waste any. Add stainless steel needles for reinforcing. Start at the bottom and create a horizontal ledge that will take the next layer. Work in this way until you get to the top. Cover for 24hrs.before removing the sand. You do not need to damp cure calcium aluminate cement for a week like you do with calcium silicate cements, 24 hrs is sufficient.

[kstronach]

Re: low cost wfo build

Thanks both.

I was thinkin of using a homemade mix for the dome rather than the expensive bought stuff. I was thinking calcium aluminate cement fire clay and silica sand at about 1. 1. 4 would this be anygood? Or does anyone have a better mix? Any idea about temperature in a cast dome? Would in need to vermicrete over that say another 2" or use thermal blanket?

Cheers

[david s]

Re: low cost wfo build

Yes you could use a mix like that, but you're in unchartered waters. The calcium aluminate cement is still really expensive stuff and tricky to use. You can do it even cheaper using 4:1:1:1 sand,fireay,Portland cement, lime. Either of the two brews will require added fibres (fine polypropylene ) which when mixed really thoroughly (about twice as long mixing that you would normally use) produce a network of tiny pipes, after they melt away at 160C, that moisture can escape through,Also it is advisable to add 2% stainless steel fibres , by weight.

[kstronach]

Re: low cost wfo build

hi david,
i am starting to think that casting the dome isn't the way forward seems like more people would have attempted it if it was a cheaper and feasable option but no one seems to have gone that way so maybe that should tell me something!!

since posting on here i have been able to source some old red clay solid bricks i could build my dome with would these work ok? how would they compete temprature wise compared to firebrick, if they were insulated well after i built the dome? has anyone built an oven with these? before we had firebricks these must have been the norm for hundreds of years right?

keith

[david s]

Re: low cost wfo build

Plenty of folk have built ovens with solid reds. The problem is that you have no way of telling if they're suitable or not. The composition of the bricks will vary enormously depending where the clay has been sourced. They are not designed for use with fire, although on the other hand they may also be perfectly adequate. If you got them cheap or free, then if it were me, I'd be inclined to use them anyway. Might be advisable to use firebricks for the floor though.

[Bookemdanno]

Re: low cost wfo build

Hi there!

I've got Victorian full clay reds for the dome of my oven! Storage heater bricks in the floor. All free, due to budget restraints too. Stay away from dusty very soft reds though.
My digital thermometer tops out at 550c and it can get there after 45minutes at the top of the dome, with 450c+ at the floor. You can cook in it for 2 days after easily on the residual heat.
Insulation is 1" Ceramic Fibre, 2" Rockwool Fire Blanket, 2-3" Vermicrete and Lime Render over. Its not had much use over a prolonged period as its inly just finished, but there is no damage internally yet.
Good luck with the build! Keep the photos coming!

[kstronach]

Re: low cost wfo build

hi danno,

thanks for the reply!
just had a good read through your build thread, nice work!! that is pretty much what i have in mind minus the awsome bbq area and surrounding features! good to hear the red clays are working too that gives me some piece of mind!!
probably no photos till in the new year now although you never know i may get the footing in and the blockwork base!! did you cast a slab or something, tied in with re-bar inside your block work to bed your concrete flags onto? also is your oven 36" internal? how high is your dome internally?

again really nice work! makes me even more eager to start mine!!

keith

[Bookemdanno]

Re: low cost wfo build

Thanks Keith!
I set a concrete lintel diagonally across the 4" blockwork parallel to the front opening, and then set 2" 3'x2' Council Type paving slabs over. The front arch supports the leading edge of the slabs. Then an insulating layer over the slabs of 4" Thermolites, laid on the side. I can say that underside of the slabs is barely warm to the touch, even on a full Hell-firing!
I adjusted the diameter slightly to suit my heater bricks and quarry tile hearth, along with the first course. Lots of full scale sketches helped here, but i'm pretty close to a 90.
Your dome height should be half the diameter for a Pompeii. Look up the "indespensible tool" on here. It works perfectly, but worked out too slow for me and the higher brick courses. Hence my wooden form.
Keep a keen eye on Ebay and sign up to Freecycle if you're on the look out for materials. Its amazing what comes up!
I see you're also on the UK forum too!

[UtahBeehiver]

Re: low cost wfo build

Keith,

I see you are in good hands with Bookem...............good luck with the build and send pictures.

[kstronach]

Re: low cost wfo build

cheers for the tip on freecycle!! already found some flags not to far away from me!!
in your opinion how critical do you think the vermicrete layer is over the rockwool? do you think it would be possible to render straight on to the rockwool and the oven still perform well? just i think i am quite tight for space and was hoping to get my oven on to a 4' by 6' pad (four 2' by 3' flags) that allows me 32" internal size and allowing for all sides 9" brickwork 2" thermal blanket 4" rockwool and 2x coat of render which brings me to very nearly 48" or 4' in width!! does setting your base at 45 degrees like you have allow for better space usage or was that just a personal preference? i'm going to get out in the garden this weekend anyway with the tape measure and have a good measure up if it ever stops raining!!!

[Bookemdanno]

Re: low cost wfo build

Rockwool is very soft, so i'd probably say it'd be best to go 2" Ceramic Blanket, then 3"-4" Vermicrete, then the render. The Vermicrete will insulate well, not as well as the Rockwool, but provides a really good intermediate layer and base for the Render.
Render over Rockwool would be tricky to achieve and could be susceptible to damage easier as it'd be more of an eggshell, so you'd possibly need a good 2" of render.
My angled approach was a preference, but i wish i'd made a circular one in reality!
I'll have a measure up at the weekend, and let you know my ovens dimensions in relation to the pad size.
Catch you later.

[kstronach]

Re: low cost wfo build

hey danno,

hows the oven doing? you had it lit recently? so tomorrows the big day for me finally making a start on the oven!! hoping to get the blockwork up in the morning for the stand, i'll start a build thread and post pics as i go so hopefully people can chip in with advice throughout the project!!

just a quick question if i may? what mix did you use for the dome construction? did you use fireclay? i was thinking something along the lines of 6,1,1. 6 silica sand, 1 lime, 1 cement. is that similar to what you used? also thought about adding 1 sharp sand in for a bit of extra strength.

keith

[bobnealy]

Re: low cost wfo build

now this is cheap way to go
Garbage Can Pizza Oven SamanthaMenzies.com