Hello & Is my idea for an oven viable?

[utopiangames]

Hi everyone,

I've been reading forums and watching video for a few days now and ready to take the plunge and attempt my 1st pizza oven.

Wondering if this is viable?

Make the inner dome from 2 parts sand and 1 part clay mix about 3-4 inches thick over a mound of wet sand and newspaper.

Cover the dome with ceramic fire blanket 25-50mm

Cover fire blanket in chicken wire then cover with a smooth exterior render to protect from the rain.

Paint render in masonary paint.

Im wondering as this seems the cheapest way to make the dome if its viable or is it flawed?

For the floor of the dome I'm planning to use 4 concrete slabs 600x600 with a vermiculite board on top of the slabs and on top of the board place the fire bricks with the down on the outside of the bricks.

Regards,

Darren.

[5leafclover]

Sounds about spot on to me. Well researched by the sound of it. Whether its cheaper, its hard to say.

My other thought is for the price of fire clay. It seems to me that half the price is for delivery. So if you can find a local supply, that would really help.

You might want to think about building the sand former over a cheap rough shape too. Something like polystyrene packing. Itll save on sand and should stabilise your sand dome too. Just make sure its something you can remove out the door once built.

[cobblerdave]

G'day
Sounds like a viable way to build an oven. Yes there are many ovens built this way.
I wouldn't "seal" the oven in with a clay dome. It's better to have it breath CF insulation or not.
Better time and money spend on overhead cover I recon
Regards dave

[utopiangames]

Thanks for the advise guys, I've just been offered some old red reclaimed bricks @ 55p each so now I'm thinking should i make the dome from lots of half bricks instead of the clay sand mix as it would last longer?….my head hurts lol.

The only thing putting me off doing a brick dome is the mortar is very expensive and I'm guessing id need a lot?

[chas]

You don't need mortar to stick old reds together for a dome - ordinary potter's earthenware clay will do, mixed 50/50 with sand. It's what reds are made of, after all. A local craft place may sell you some, so delivery not an issue. I think I used about 2 buckets, maybe less, but it's so cheap you really can't worry about the cost. I was lucky - my potter had over watered a batch and gave it to me as useless for pots. The extra bonus is it literally sticks the bricks together - no need for a former and you don't have to wait for mortar to go off as the dome goes up.

Chas

ps mortar costs? Lime putty mortar by the tub, about £22, I needed 2 for the brickwork without the dome.

[utopiangames]

Thanks Chas, i didn't realise you could use clay and sand mix for the mortar it will certainly be cheaper! Im guessing i can use it for the brick entrance arch also?

[oblertone]

Have a look at my build thread (below) as I used old red half bricks; as to mortar being expensive, I used sand & cement from wickes, lime from a local source and a bag of fireclay. Can't recall but it wasn't more than £50 all in; although I did buy a cement mixer for another £50. I used a ratio of 3-1-1-1 for my dry ingredients, known hereabouts as homebrew.

[chas]

Oct 16, 2015 13:50:04 GMT utopiangames said:

Thanks Chas, i didn't realise you could use clay and sand mix for the mortar it will certainly be cheaper! Im guessing i can use it for the brick entrance arch also?

No, only the dome if it's clay/sand - because you'll be waterproofing it somehow the clay won't suffer from wetness which might weaken it.

While I'm at it: don't be in too much of a hurry to clad the dome, however bonded, because you may seal in construction dampness and as CobblerDave told me - steam can really hurt a dome.

Any exposed brickwork needs conventional cement or lime mortar for stability.

Chas

[5leafclover]

Oct 16, 2015 14:43:52 GMT oblertone said:

Have a look at my build thread (below) as I used old red half bricks; as to mortar being expensive, I used sand & cement from wickes, lime from a local source and a bag of fireclay. Can't recall but it wasn't more than £50 all in; although I did buy a cement mixer for another £50. I used a ratio of 3-1-1-1 for my dry ingredients, known hereabouts as homebrew.

Using 5-1-1-1 homebrew here too and it seems to work and doesn't cost too much either. Fireclay was the expensive bit at around £20 for 25kg, Hydrated lime around £9 for 25kg. It seems to crack a bit when it dries, but I think that's down to the clay and large mortar joints of the arches.

[utopiangames]

Great advise guys, homebrew sounds interesting.

I've just ordered everything i need to build the base and oven for just under £300 next door is a manager at Travis Perkin so got a good deal on some items.

I still need the ceramic fire blanket but need to look around as they seem expensive and I'm not sure how much I will need for a 36" interior oven.

My other half works at a school so has ordered me some 12.5kg bags of terracotta clay for £2.50 with free delivery so I'm guessing the final build price will be around £400 all in suited and booted with chimney and painted, does that sound about right.

[chas]

Oct 16, 2015 17:29:39 GMT utopiangames said:

Great advise guys, homebrew sounds interesting.

I've just ordered everything i need to build the base and oven for just under £300 next door is a manager at Travis Perkin so got a good deal on some items.

I still need the ceramic fire blanket but need to look around as they seem expensive and I'm not sure how much I will need for a 36" interior oven.

My other half works at a school so has ordered me some 12.5kg bags of terracotta clay for £2.50 with free delivery so I'm guessing the final build price will be around £400 all in suited and booted with chimney and painted, does that sound about right.

Well done on the clay - get your friendly TP neighbour to add a plastic mortar mixing board (4' square shallow tray) - it's ideal for trampling clay and sand together into a usable mix.

As for blanket, estimate the outside diameter and work length to wrap around from there... I got mine from eBay, £36 for 7+metres of one-inch and used a double layer: ukwoodfiredovenforum.proboards.com/thread/2187/give-pompeii-retro-fit-insulation

Chas

[utopiangames]

Thinking about homebrew and see 2 different ratios above one is 3-1-1-1 other is 5-1-1-1 which one is correct?

Also if i go with this will ordinary builders sand & general purpose cement be ok?

I'm also presuming fire clay is in a powdered form and not solid clay?

[xxxdvxxx]

hi if you shop around i know you can spend at bit more and get firebricks about 80p each im off to stoke,stoke would seem to be the closest place thats sells clay firebricks cheap next nearest to me was chester the birstol, on monday, as the place isnt open weekends, to check out some and bring back at least 50 either way im thinking of doing my dome the simaler but adding fire brick grog into my fire clay and sand layer,1-1-1 and instead of a blanket layer then was goin to do a layer of fireclay vermlite granules and sand then old red bricks/fire bricks with homebrew 3-1-1-1 for outside

[5leafclover]

Oct 17, 2015 11:44:15 GMT utopiangames said:

Thinking about homebrew and see 2 different ratios above one is 3-1-1-1 other is 5-1-1-1 which one is correct?

Also if i go with this will ordinary builders sand & general purpose cement be ok?

I'm also presuming fire clay is in a powdered form and not solid clay?

My fire clay came in powdered form. I assume thats normal.

Time will tell whether my 5:1:1:1, with ordinary sand and cement will work. The arches seem solid but have yet to fire the oven.

Regular mortar can be mixed anywhere from 3:1 to 6:1, so i dont think its a right/wrong answer kinda thing.

[cobblerdave]

G'day
6:1:1:1 would be my preferred mix. The 3:1:1:1 is basically a 50/50 mix when you think about it.
The Portland cement, the lime and the powdered clay are all the "cementious" parts of the mix really.
So why have all these diferent cementious parts. They perform diferent tasks.
The powdered clay enables the mix to stick to the brick and allows a certain amount of movement in the brick before it losses bond and needs the mortar to be reapplied. It can be any powdered clay really as our ovens operate under 1/2 the temp that fire clay is designed to operate at. It dries out in the high temp ever time and become super dehydrated rather than fired.
The Portland cement provides the fastest "set" of the 3, and gives you the first set . It's effected by the heat over 300C and breaks down over time.
As the Portland cement breaks down the hydrated lime sets in the heat and takes over from portland as the fireproof cement in the mortar.
Is there a standard for "poor mans mortar" there isn't and never will be as it's not a commercial product. If it was a proprietary mix it would have a standard and be tested to a standard. Ever mug can make it so there's economic reason to standardize it.
Regards dave