In the early years of JUCA, many contractors preferred to build a firepit on-site, which the JUCA B-3C sat upon. (Actually, the same thing was true regarding built-in fireplaces, and so our old F-Series units ALSO had an open bottom). They had many skilled masons available, and they felt that this situation allowed maximum flexibility in the design of the masonry design. Often, those firepits would blend into adjacent seating areas and/or back into the wall behind the fireplace. They would sometimes have interesting and unique shapes, exterior appearances, ash dump chutes, and just generally allow a LOT of creativity to be incorporated. Considering all the ridiculous numbers of choices JUCA allows customers, it seems appropriate that we initially leaned in the direction of this type of unit.
Over the years, however, this has gotten less popular, where contractors now tend to want a complete unit to plop in place and then to put a veneer masonry facing around the bottom part. (For imformation sake, some ALSO have veneered over the upper part, too. If you consider doing this, just keep in mind that those front corner posts between the glass walls on the JUCA are NOT meant to support tons of brick or stone!) Such "modern" needs are fulfilled by JUCA's Model B-3D unit.
For those who want or need extra flexibility of design, JUCA still offers the B-3C style units. There are several sizes. These units HAVE NO BOTTOM! It is OPEN, only surrounded by a one-inch wide supporting frame. In effect, the JUCA B-3C-style units only include the upper half of the finished firebox. The lower half must be constructed on-site.
Such a firepit has a number of safety restrictions. First, it must be built over totally non-combustible materials. No floor joists, plywood or any other wood materials may be anywhere beneath the firepit. If such materials exist, either they would have to be cut away and removed or JUCA's Model B-3D unit must be used. If an EXPERT in fire safety was involved in design, there actually ARE high-tech ways of shielding all heat from going downward, but we DO NOT encourage thinking in this direction, since the B-3D Series units are available for such applications.
The firepit structure must again be totally made of non-combustible materials. It must also support its own weight (maybe 800 pounds) and the weight of the JUCA above (600 pounds more). Of course, the concrete floor or foundation beneath it must be able to support this weight, as well. The narrow (one-inch wide) support frame of the JUCA B-3C style unit above must rest solidly ON the top surface of the base so as to be adequately supported.
The general concept of the C-style base is shown in the drawing. The main structure of it is built of standard 4.5 by 9 by 2.25 firebrick, mortared together with appropriate fireclay. The outer surface can be any non-combustible materials, such as veneer brick, veneer stone, ceramic tile, marble, slate, copper sheeting, etc.
The TOP of the base can be treated in many ways. Sometimes, people have turned facebricks sideway on edge, like window sills sometimes are in brick homes. But more commonly, people like the appearance of a hearth stone on top, often a limestone slap from a local lumber yard. These, again are normally used as window sills in brick houses. Such limestome slabs are usually 2.25 inches thick and in any width divisible by two (6, 8, 10, 12, etc). Of course three pieces are needed to top the C-stype firepit. Many years ago, we discovered an important detail regarding this. It is a VERY good idea to mount the limestone about an inch OUTWARD from being flush with the INNER surface of the firebox. The cut firebrick into one inch wide strips to fill this space. The point of this is to protect the inner edge of the limestone slab from the heat of the fire. It turns out that they normally store this limestone outdoors, where it gets rained on. So it absorbs moisture. When the heat of the fire gets to it, the water might boil, and form hairline cracks in the limestone. The procedure we described avoids this possibility.
During the construction of the firepit, many options may be incorporated. A gas-line stub supply pipe may be installed. An ash-dump or ash-drawer could be installed. Outside combustion air intake may be provided. The outer surface may be covered with marble, slate, tile, veneer brick, veneer stone, flagstone, etc., etc.
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