First Questions before commencing build

[craigball]

Dear All

I am hoping that some of the more experienced building on here can offer some advice on a few questions I have before I start construction;

1. I am planning on approx dimensions for my barrel/vault of 600mm(W)x 1000mm(L) with rough Heigh of 400mm(at apex of arc)
2. Do I need to use fire cement for the entire brickwork Barrell/tunnel?
3. Is there a mix of 'normal' muck that can be used for the Barrel/Tunnel/Furnace?
4. Is it better to insulate the Barrell/tunnel with Vermiculite Granules and then render over the entire thing to add some heat insulation?


If there are any other important points you feel i should ahve covered please feel free to add your comment.

Look forward to hearing from you all

[jms]

Mortar: Google "homebrew fire mortar", it'll bring up lots of results from this site and others about mortar for pizza ovens. Homebrew mortar is a mix of around 6:1:1:1 parts sand, cement, fireclay, and hydrated lime. Commercial fire cement is not as good for the wide gaps which DIY ovens produce, and is much more expensive.

Insulation: Definitely insulate unless you don't mind wasting a load of energy (firewood £££). Vermiculite works well, others use insulating blanket, or a mix of the two, the former is pricey but efficient, later is cheap but less effective (needs to be thicker). If you use Vermicrete then you have to drive as much moisture out as possible through firings before putting on a final decorative render, else the finish will crack badly under expansion and steam.

[cobblerdave]

G'day
Rough rule of thumb with insulation is that 2 inchs of Ceramic Fibre blanket is roughly equal to 4 inchs of Pearlite cement in its insulation value.
1 inch layer of pearlite cement should be left roughly a week in good drying conditions till the next inch is applied.
Regards Dave

[moonhead]

Hi Craig, you don't want to be using fire cement for the chamber of the oven unless your going to taper the bricks for a tight fit. It's only recommended to use for joints of around 3mm so as JMS said home brew mix would be the better option. I used the fire cement on my build and Kiln Linings arch kits so the gaps were pretty slim but have noticed on a couple of the thicker joints some of the fire cement has gone.
As for insulation - the more the better, I have 2" inch blanket plus 3" vermicrete two mortar based render coats to keep it dry.
One thing I would suggest is increasing the width of the chamber as long as you have space to do so. Mine is 700 wide and if I get the chance again would like a little more, even if only 50mm.
Good luck Rick