3.2. Form supports.
The Side Forms
Next, build the sides of the form using either 2”x4” or 2”x8"
lumber to fit around the block stand edges. This frame
forms the sides of your insulating hearth. The form board
will be set at the top of the outer edge of the block wall,
and will need to be supported by 2”x4” legs and shims.
3.3 Form sides held in place with 2”x4” supports.
The Bottom Form
Cut the sheets of
½
” Hardibacker to fit inside the wood
form and lay on top of the block stand. If you are using
plywood, cut it to fit into the opening (3/8" shorter so that it
will easily come out later), and lay it on the frame. Tape the
joint with masking tape. Set your last two 2"x4" legs
supporting a 2"x4" on its side directly under the joint,
which will support the weight of the wet hearth while it is
curing. Shim to level. You have finished the bottom of your
form.
3.4. Hardibacker and form set in place.
For the two-layer hearth, draw a line 4” down from the top
of the frame to mark the top of the structural concrete
layer.
Lay a grid of 1/2" rebar slightly shorter than the external
dimension of the wood forms, on 12" centers, starting 6" in
from the edges of the form, set half-way up the 3 1/2”
concrete layer (about 1 3/4”). Then, pour the 3 1/2” layer of
structural concrete.
3.5. Rebar set in center of the concrete pad.
Casa Installation and Operating Manual
© Forno Bravo, LLC 2008/9. All Rights Served.
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