Installation guide

Pompeii Oven Instructions
© Forno Bravo, LLC 2007. All Rights Served. Ver. 1.2 22
3. Framing the Hearth
Overview
Your oven sits on a two-piece hearth, comprised of an
insulating layer that rests directly under the oven cooking
floor, and a structural layer that hold the oven in place.
The insulating layer stops heat from leaving the oven
through the cooking floor, and is made from either 3 ¾” or
4” of insulating concrete (vermiculite or perlite mixed with
Portland cement), or a 2” calcium silicate insulating board
(SuperIsol) available through the Forno Bravo Store. The
structural layer is comprised of either 3 ½“ of rebar
reinforced concrete, or a fabricated metal tray. For
installations that will use vermiculite concrete for
insulation, the structural concrete and insulating concrete
are poured in two parts in a single form built from 2”×8”
lumber (1 1/2″ × 7 1/2″, 38×235 mm) and either 3/4"
plywood or concrete board to form the bottom of the
hearth.
For installations that will use SuperIsol insulting board, the
structural layer can be poured separately in a form built
from 2”×4” lumber (1 1/2″ × 3 1/2″, 38×235 mm) and either
3/4" plywood or concrete board to form the bottom of the
hearth.
Island Hearth
Some builders want use their oven for baking multiple
batches of bread from a single firing. In this application a
little extra thermal mass in the floor will allow longer
cooking times at elevated temperature. This can be
accomplished by using what is called an isolated hearth. A
ring of refractory concrete in poured to the same diameter
of the dome about 1 1/2” thick, or an island of firebricks is
set under the cooking floor. You may either pour extra
insulating concrete around the island or leave it elevated.
You may also use firebrick splits (1 1/4") to increase the
mass (Photo 3.1). You may “sink” your island into the
insulating layer, but take care to not reduce your insulating
layer to less than 3 1/3 inches.
Take care with the additional mass under the oven. All
Pompeii Ovens with a standard 2 ½” firebrick cooking floor
are capable of retaining enough heat for roasting a turkey,
or baking a full oven of bread, from a single firing.. If you
are not going to be baking very large volumes of bread,
you probably do not want, or need, the extra mass under
the oven floor.
3.1. Firebrick splits under the cooking floor.
Thermocouples
If you are planning on using one or more thermocouples in
the hearth and/or cooking floor, you can add them now.
You can either include the actual thermocouple wire in the
hearth when the concrete is poured, or you can use a
straw to create a chamber where you will run the
thermocouple wire later. (See Photo 3.4)
Instructions
The hearth form is built in two parts: a bottom tray and the
frame sides, which will hold the hearth as it is poured.
After the hearth has cured, the form is removed (and
usually becomes part of the first fires that will cure your
oven).
Support for the Tray
First, using 2 "x 4" lumber (or 2 "x 3") set on its side, build
the frame for the bottom of the form. The frame should be
roughly 3/8" smaller than the opening of your block stand,
so that it can be easily removed after the hearth has
cured. (Photo 3.2)