3.6. Structural layer waiting on insulating layer.
Next, lay your insulating blocks in the center of the hearth,
making sure the Casa oven floor, vent landing and dome
will rest completely on the insulating blocks.
3.7. FB Block set in wet concrete.
Using Insulating Concrete
If you are using insulating concrete under your oven,
rather the FB Board, make sure you have built your form
to allow for the extra 4”. Prepare the insulating concrete
using a ratio of 5 parts vermiculite to 1 part Portland
cement (5:1). Thoroughly mix the vermiculite and Portland
cement when they are still dry, then add water and mix
until you reach an oatmeal consistency. Pour the insulating
material to the top of the form.
If you will be building a landing in front of your oven
opening, it is not necessary to pour vermiculite concrete all
the way to the front of the hearth. Rather, you can end the
form where your oven vent will begin, and only pour
vermiculite directly under the oven chamber and vent
area. Fill the form under the landing in front of the oven
with standard concrete.
3.8. Insulating concrete on top ready to cure.
3.9. Vermiculite concrete poured under the oven chamber.
Tips and Hints
Cut your frame and plywood for the bottom of the hearth
form about 3/8" shorter than the actual opening. The
concrete will not escape when you pour, and it will be
easier to remove the form when your hearth has cured.
We recommend mixing your vermiculite concrete by hand,
rather than in a mixer, which tends to break the vermiculite
up and reduce its efficiency. It is a light mixture that is easy
to work with. Dry mix the vermiculite and Portland cement,
so that the cement covers the vermiculite, then add water
until you reach an oatmeal-like consistency.
Casa Installation and Operating Manual
© Forno Bravo, LLC 2008/9. All Rights Served.
Ver. 2.1
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