This install is my large semi commercial size kit, it is suited for bars, restaurants and serious home bakers.
This install is for a bloke who lives near me who runs a small tour bus operation where he takes out groups of 12-14 people to see the sights around Nelson New Zealand.
He provides morning tea and lunch and wanted to be able to serve great home made food.
He plans to serve pizza, breads and cakes baked with this oven to give customers along with a great tour, great food!
He has chosen the large oven as he can bake enough bread to feed 12 people in 1 batch and tons of pizzas while heating the oven for the baking.
By installing this oven he has saved from having to re-do his home kitchen to install a commercial size electric oven.
Having this oven will keep his profits high by not having to purchace food to serve and fuel (wood) is free keeping his overheads low with forever increasing electricity prices.
Features of this oven:
Large cooking floor 1mtr in diameter.
Extra thick refractory dome 100mm thick to hold heat for extremely long time for baking.
Low roof design to give better grilling affect on pizzas.
Easy 4 piece installation.
Customisable design so you can make it look just how you want.
Dome designed to accept a 150mm flue.
Hope you enjoy this instructable and thanks for looking.
Constructive criticism welcomed : )
Please view my other instructables for how to make an insulated door and other pizza oven installation designs.
Step 1: Making a Base 1, Bottom Slab and Blocks.
First box out your area for the bottom slab, this slab is 1400mm W X 1600mm L and including rubble 300-400mm Deep.
Extra length is added to marry up with existing bricks on the ground in the front.
I like to fill the slab with rubble so you do not have to use as much concrete, some people will say this makes it stronger but personally i do not have a lab to prove this point.
Also scrap steel is thrown in for reinforcing, we are not building a house and will not have building inspectors so just throw all the junk you have in there, prop up some of the bars with stones so they are not just sitting on the bottom.
Give all the rubble a clean with the hose to get any dirt and loose material off it, also getting it wet will make it so the old concrete will not suck the moisture out of the new concrete you pour making it weaker (again no lab tests sorry).
This slab is a 6 part (concrete aggregate) to 1 part (Portland cement) mix.
Each mix is dumped into the boxing and spread out and rubble jammed in, i think it took 5x mixer loads to do this slab.
The concrete is then roughly smoothed off with a wooden trowel, left for an hour or so (depending on ambient temperature and humidity) until the excess water has evaporated and worked its way to the surface. then smoothed off with a finishing trowel.
You will feel that the concrete has gone fairly stiff by the time it it is ready for finishing.
Once finished it is covered with a tarp and left for a week or so to cure.
Next remove the boxing and start with the blocks.
I use a 3 part sand to1 part Portland cement and 2 caps (40ml) of plasterciser for the block mortar mix.
Wack all the blocks up to the height you want then cut lengths of re-bar that are 50mm higher than your wall so you can tie your horizontal re-bar for the slab to these points... its up to your personal preference where they are placed and how many you put in.
Fill the hole with concrete and use the length of re-bar in a stabbing motion to make sure all the voids are filled and then leave the re-bar centered and pushed to the bottom.
I only filled the holes with the re-bar at this stage, not quite to the top... this will help the slab you pour lock into the blocks better and the other holes filled when pouring the slab will fully be connected all the way to the ground providing excellent strength.
You could stagger the blocks if you want, for such a small block wall the and the time spent cutting blocks i dont think it is necessary.... although in the rear i have staggered as there needed to be 1/2's cut.
Please view the pictures to see placement of re-bar and blocks that i staggered.
Step 2: Base 2, Re-bar, Boxing, Slab, Insullation, Fire Bricks, Tiles.
After leaving for a few days its time to make the boxing for the slab.
Old wood in the workshop and some pallets broken down comes in handy for this.
Best just to look at pix rather than try to explain... the few things to note are:
The side boxing has marking on it, 100mm and then 200mm to the top... the first pour will only go up to the 100mm mark and the 2nd pour will go to the 200mm mark.
Potters clay is use on the boxing to fill any gaps and around all the edges, this makes the corners rounded and nice and concrete not run through any gaps when vibrating.
Legs for the floor boxing are cut short and another piece of wood screwed to extend length, this will make them much easier to remove when the time comes.
A sheet of plastic is placed on the plywood floor to make a nicer finish on the underside.
Re-bar is then cut and added to suit and tied in a grid style.
First slab is then layed up to the 100mm mark and left for a few days to cure...
I like to use a hammer drill on the outside of the boxing to remove air bubbles and any voids.
A 5-1 mix was used for this slab.
Again it is troweled flat with a wooden trowel and finished an hour or so later with a finishing trowel.
Suss out where your front tiles or whatever are going and cut etc so they are ready to throw in when the 2nd slab pour is done.
Insulation & fire bricks.
Crematic fiber board is then place on the slab, then HD tinfoil and fire bricks laid dry on top.
Then edges of the fire bricks a wrapped with a strip of crematic blanket to make sure the fire bricks are completely isolated form any concrete.
A length of wire is used to hold this in place ant tied tight.
Then the rest of the slab is poured then vibrated again with a hammer drill.
Tiles are then placed to marry up at the same height as the fire bricks.
The next day clean up the tiles with a damp sponge and remove concrete stains.
Step 3: Erecting the Dome.
Place a piece of cardboard or foam etc on the fire bricks as you will not be able to put a piece up in 1 movement, then you can place a dome piece onto the cardboard on its back, jump up onto the structure and lift it into place.
Try to avoid dragging or leaning the piece on one edge as they can chip so be careful and do not rush.
If all your fire bricks have been placed perfectly you will be able to use the lines on the fire bricks to find the 1/2 way point where the edges of the dome pieces want to sit.
Get them all up and then tweak as necessary.
The first bit will need a bit of wood or something to hold it in place but the rest will just stay there by themselves.
If it is not aligning perfectly you may need to use packers in some spots, little bit's of stone etc are fine to use.
Once you have them all sitting perfectly you should be able to slap the bits with your hand... they should not move at all.
Then grab your refractory mortar and glue it all up... 2 ltrs are provided with the kit but only mix up say 500mm at a time.
Make the mix fairly stiff, if to runny it will crack more. when it dries... just add a little more pouder if its to runny.
Push it hard into the joints with either a little trowel or just use your finger.
You can do the inside joints if you like but it is not necessary, looks better if you just leave them.
Step 4: Flue and Damper.
Thicker steel would be nicer but i had 3mm steel laying around so that's what i used.
Step 5: Insulation Blanket, Chicken Wire, 1st Render Coat.
This seems to be the easiest way to do it, just make sure you overlap any cuts you make.
I would recommend covering the corner fire bricks that come out the sides too, the idea is you just want to have all of the refractory and fire bricks isolated from any other concrete to stop heat sinking, this will allow it to heat real hot faster without having to heat the rest of the structure.
Then chicken wire is added over the top, you can wire across the entrance and use these wires later to hold on the front arch form.
1st render layer is then applied, a 3 part sand to 1 part Portland cement has been used... a nice stiff mix.
Start working on your finished shape form here.
Step 6: Secondary Insulation. Silica Cylinders
You should be able to get these locally for free, they are commonly found in large numbers outside houses with the lights on at 2am on a Saturday night and a lot of noise coming from the house... another tip for silica cylinder prospecting is to go to your local recycle center.
Build your beer bottles up like bricks, use as many bottles as possible packed as tightly together as you can.
Build them all up and then give them a render layer, again working on your final shape.
Step 7: Front Arch.
You can make it the shape you want but here are a few tips.
Make it larger than the entrance of the refractory dome, this will give you a recess for your door to lean against when you slot it in.
Make a taper on the arch form so it is larger at the front and is smaller at the rear, this will make slotting the door in easier and will get a tighter seal when the door is in place.
A thick piece of cardboard is lent against the oven before the arch form is put in place.
This will provide a thermal break between the main oven and the front arch, will reduce the chances of the arch getting cracked from the heat and isolate it from the hot refractory.
This cardboard also has the shape of the front arch drawn on it, with lines drawn from the center to the outside so you know what angle to place each stone at to give a uniform finish.
Here i have just used a local stone from a valley a bit over from me, you can use anything for this front arch, bricks, bottles etc or you can cast one... just use what will look good with your surroundings.
I have used a mortar mix the same as the final render coat with colored red oxide.
Use your left over mix for a splatter coat for your final rendering.
Step 8: Final Render Layers.
So after you have done a splatter coat, this will help the render stick mix a big batch up.
Im using a 3 sand to 1 Portland cement mix but have made a double batch... best to make it in a single batch so the color is uniform.
This mix is, 60ltrs sand, 20ltrs cement, 1kg red oxide, 500ml waterproofing additive.
2 layers are added, first one about 10mm thick and the second about 15-20mm thick leaving no less than 24hrs between layers.
Mix it up and get it on.
Step 9: First Firing and Finishing.
Refractory cement unlike most other cements cure fully with firing.
If you have it on hand, a LPG gas burner ring is good to use for this as you can control the flame size, as most people will not have one i recommended making the smallest of fires and keeping it going all day.
It is best to use small bits of rotten wood, or charcoal this will burn but will not create high temps.
You can control the fire if it starts to get too big by blocking the door and the flue starving the fire of oxygen, this will most likely be a smokey process but is worth it.
What can happen if your fire is to big at first firing is, the moisture still inside the dome pieces will turn to steam and start spitting pieces of refractory... also can make large cracks.
Here is the manufacturers guide, it is based on 250mm thick for a kiln, as this is nowhere near that thick you can 1/2 the times in this guide so try to keep it at 100-120 deg c for a day, then next day slowly bring the temps up fully watching for any sign of steaming.
Due to the fact the rainy season has just started, this oven has been covered and will have the final finishing done in a few weeks.
I will add these steps when it is done and some other photos.
But just a quick guide, use a concrete sealer on the exterior once it has been fired a couple of times and moisture has completely evaporated from the oven and external render layers.
You can check to see if there is still any moisture coming out by covering the dome with a tarp and leaving it for a few hours, when you lift off the tarp there will be condensation built up on the under side if there is still moisture coming out.
Once all the moisture is gone apply a few coats of concrete sealer, i recommend this type for kiwis:
"CEMIX DRIVESEAL is a clear high build, GLOSS finish, thermoplastic solution that protects and highlights the colour and texture of the underlying concrete surface. It has been developed exclusively as a drive and paving coating which is UV stable."
More photos to come, check back in a few weeks : )