Design phase of my new WFO at the Cove

[Cookie Monster]

Hi Tommmo,

Just noticed your comment from a year ago or so. This is the Tile Saw I used.

Your build is looking good!!

Cheers,

Matt

[david s]

Most builders like to try and slow down the heat transfer from the dome to the flue gallery in an attempt to reduce it acting like a heat sink, so place their heat break between the two. My build is rather different in that it is cast and my flue gallery only weighs 10 kg so the heat sink effect is reduced. For that reason and because of my floor design, my heat break/ expansion joint is between the flue gallery and the outer decorative arch. Because this position sees lower temperatures it has advantages in the materials used. I use 5:1 vermicrete in the gap but the fibreglass rope should be ok so long as you can find a way to prevent loose fibres falling into your food.

[cnegrelli]

David - do you employ a heat break on yours? It seems like your chimney flue is compressed into the dome so far, that there's really no "entry" to speak of, so I've sort of concluded that the builds you show here do not employ one.

[tommo21]

Thanks David. The more i ponder the heatbreak i am drawn towards the ceramic rope or tape say 50mm x 3mm at a guess between the inner arch face and the vent arch. and depending on availabilty and cost seem a luxury still.

[david s]

Remember that if you design a heat break although it may prevent a little heat from conducting to the entry,, being so small, usually around 10 mm or so, is not enough to be of a major benefit. You wouldn't expect 10 mm of underfloor or dome insulation to be particularly effective in preventing heat transfer. The heat break's primary function IMHO is to act as an expansion joint, preventing cracks to the outer shell. This can only be achieved if the material used in the gap is somewhat flexible. A section of stainless tubing for example, is not. It may look smart but won't be able to absorb any expansion from the hotter inner oven.

[tommo21]

Thanks again David.
After more reading on vent arch temperatures other builders have shared, I am less concerned about the heat break. Avoiding creating a heat sink with the vent arch makes sense - but ensuring the fire bricks in the working area are not scolding is probably more important. I think i will take my outer insulation blanket over the vent arch anyhow.

I have started a thread for my build stage now - i will post any further questions there.

Cheers.

[david s]

All experienced builders - do i need to extend my floor insulation layer out under the vent landing?
And does a IFB covered with SS sheet sound like a reasonable floor heatbreak? would the SS be dangerously hot to the touch if i were to brush my arm over it?

If you are wanting to limit the conduction of heat by using IFB's, then placing a highly conductive material (more than 10 x more conductive than dense brick), bridging over them is counter productive. Yes it will get hot. If you must use it then make it as thin as possible e.g. 0.55 mm

http://www.engineeringtoolbox.com/th...als-d_858.html

[tommo21]

I finally collected all materials and have made a start on the oven.
My concrete slab includes plastic sheet beneath, a waterproof additive to the concrete, tile waterproof membrane and porcelain tiles to raise the insulating board off the slab to avoid wicking.
Probably overkill but my oven is not raised as is traditional and i am trying to keep the oven dry.
I will start laying floor bricks tomorrow. Hopefully i can take a little of the unevenness out of the cal sil board with the sand fireclay mix.
Cheers

[tommo21]

All experienced builders - do i need to extend my floor insulation layer out under the vent landing?
And does a IFB covered with SS sheet sound like a reasonable floor heatbreak? would the SS be dangerously hot to the touch if i were to brush my arm over it?

[UtahBeehiver]

Nothing wrong with repurposing. A good portion of my build was respurposed, salvaged, or scrounged materials.

[tommo21]

The suspended slab ended up between 120mm and 150mm thick or 4-6"

[tommo21]

[tommo21]

Some pictures of works so far.
I am trying to reuse materials on hand, so you will notice some unorthodox or not so pretty building methods and results...

[tommo21]

Thanks Utah, Alex has done some fine work there. That stand footing would've taken some filling too!
I really like his render finish and face brick integration.

[tommo21]

Thanks Gents,
I still have a bit of time before i begin cutting so i will look in to all the options mentioned!

To check my plan of attack though, these are the steps i am planning to take to get started.

1. Concrete hearth is curing - i want to add a plastic or painted membrane on top of the slab to stop rising moisture.

2. I have read that a 'drainage layer' is a good idea (Randy J's idea?) to get the insulation off the hearth - so i was planning to lay concrete pavers on the hearth. But i am considering Hebel (aerated concrete i think) for this layer. i have seen hebel used on some Aus build as the insulating layer also.

3. insulating layer - either insulating firebrick, calsil board, ceramic board, or hebel if efficient? Open to all options here and i probably need to research a bit more.

4. Then the cooking floor inside the dome using standard 75mm thick or 3" fire brick for the floor, probably herringbone pattern.

I have materials to source and i need to weather proof the area a little bit to start as we are just about hitting the depths of winter here - no snow like the USA builds - but plenty of moisture which could ruin some materials.