Several years ago, while on vacation at Disney World, I was
struck by the variety of "brick" and "stone" surfaces created
with cast concrete. My partner, Keith Knickerbocker, and I
wondered whether it would be possible to use this method to
manufacture a good-looking precast fireplace and chimney system
that could be delivered to job sites in sections and erected
with a crane.
We were sure there would be a ready market for such a product.
In his 20 years as a general contractor, Keith had experienced
the expensive delays that can occur when the mason is running
behind schedule. This has caused many builders in our part of
southern New England to exchange traditional masonry for
"zero-clearance" manufactured fireplaces and metal flues. This
is a workable solution, but the limited life expectancy of the
metal components and the boxy appearance of the wood chase make
it a second choice for many homeowners.
Developing a System
Most precast concrete products aren't much to look at, and we
knew that builders and homeowners wouldn't accept a fireplace
that looked like a Jersey barrier. To get the level of quality
we wanted, we built a custom aluminum mold that closely
duplicates the appearance of real brick, adapting embossed
aluminum panels widely used in commercial precast work. We also
adopted the staining technique used in commercial precasting,
which creates realistically red "brick" while leaving the
"mortar joints" natural.
Taking the heat. Another
challenge was coming up with a cement formula that could
withstand the heat of a fireplace firebox. It took us a couple
of years to develop our proprietary cement formula, perfect the
product appearance, and get an approval to UL standard 127 (the
standard for factory-built fireplaces). But with the crucial
development work behind us, we can now deliver an approved
precast concrete fireplace and chimney to any job site within a
two-hour drive of our plant in Higganum, Conn. We have plans to
expand our operations within the next year or so.
Options and features.
Although the range of possible chimney styles and sizes is
potentially unlimited, for now we're making a single model,
which is available in a choice of three colors. This initial
product offering is meant to cover most standard applications.
It consists of a single firebox with an 8-inch flue and an
additional 7-inch flue for a furnace or boiler.
The 36-inch-wide by 30-inch-tall by
23-inch-deep firebox is lifted from the truck. The design
includes a 60-degree throat slope and a rounded smoke shelf for
increased performance. A built-in ash dump, with a removable
drawer, is located below the firebox.
The location of the chimney is up to the builder. It can be
lowered inside the structure before the roof goes on or
installed on an exterior wall. Most of our customers have opted
to put the chimney outside the house. Many masons and building
scientists advise against this approach, because the resulting
cold flue can lead to a reduction in draft. So far, though,
none of our customers have experienced any problems, probably
because our cast refractory has better insulating qualities
than traditional masonry. This keeps exhaust gases hot and
provides a strong draft.
Other benefits. In addition
to the obvious benefits of speed, fewer weather delays, and
improved quality control, there are other advantages to
precasting. Our refractory concrete formula contains no lime,
so it's not affected by the efflorescence that can disfigure
real brick laid in conventional mortar. The steel-reinforced,
monolithic sections are also much stronger than site-built
masonry, and there's no future repointing.
Finally, there's price. We can install a typical two-story
chimney for about $4,500, or 20% to 40% less than a comparable
site-built chimney. That's about equal to the installed cost of
a manufactured metal fireplace, which lacks the additional flue
that's standard with our product.
Planning and Ordering
Although we can go lower or higher, most of the chimneys we
sell range from 16 to 37 feet in height. But because precast
chimneys can't be altered in response to changes in the
original plan, as a site-built masonry chimney can be, careful
measurement and planning are essential.
For an exterior installation, a correctly dimensioned chimney
bumpout must be formed into the foundation. Height is also
critical. The builder needs to provide us with information on
the height of the floor system so we can dimension the cast
bottom section of the fireplace to make the hearth line up with
the finished floor. We also provide a template for proper
placement of the dowels that anchor the bottom chimney
Finally, we need to take the overall height and roof pitch
into account. We adjust the individual chimney sections in
6-inch increments to achieve the correct height and make sure
that our one-piece flashing system lines up with the edge of
the roof. To make sure this happens as it should, we require an
accurate set of elevation drawings before the foundation is
So far, most of our customers have been modular builders.
Factory construction methods practically guarantee that the
as-built dimensions will match the dimensions shown on the
plans. But a builder who doesn't have good plans could create
problems for both of us, and we stress this from the beginning.
Scheduling a delivery requires a two-week lead time. After
getting the call, we confirm that there haven't been any
significant changes to the original design and make
arrangements for our three-person crew to install the
Delivery and Installation
It ordinarily takes about six hours to complete an
installation, and we can show up on the site any time after the
foundation has been poured. When possible, though, we prefer to
wait until the house is framed and sheathed, because this lets
us install the attic tie without making an extra trip.
Site access. For best
results, we need to be able to pull our boom truck to within 30
feet of the chimney footprint. Our truck has the reach and
capacity to boom over the roof, but the lack of visibility
makes that pretty nerve-racking. It's a complication we try to
avoid whenever possible and one reason we'll consider setting
the fireplace before the house is framed.
The modular chimney sections arrive on
the site in a ten-wheel truck. It's up to the builder to
provide unrestricted access to within 30 feet of the chimney
footing so the modules can be boomed into
Stack 'em and grout 'em. When we get to the site, we
check the chimney bumpout for size and level before lowering
the first section into place. That's followed by the firebox
section, which is joined to the first with grouted dowels and
refractory sealant. The joint between sections is tuck-pointed
with mortar, leaving it indistinguishable from those above and
The chimney bumpout is poured with the
foundation but generally needs to be about 4 inches higher
(depending on the floor system) than the foundation walls. The
first section is lowered and protruding dowels are grouted into
it, making the final assembly strong enough to be completely
The aluminum flashing piece fits into the joint that falls at
the roofline. Although the chimney is designed to be completely
free standing, we also install an attic tie to appease nervous
builders and inspectors. Once the final section is lowered and
the cap installed, it's tough to tell our chimney and fireplace
Section lengths can be adjusted in
6-inch increments so a joint occurs at the roofline, where a
one-piece aluminum flashing will be inserted. Although tests
have shown that the free-standing chimney has the strength to
withstand 120-mph winds, an attic tie is also installed at this
The completed chimney is difficult to
distinguish from site-built masonry because stencils prevent
the red stain used on the "brick" from discoloring the
naturally gray "mortar joints"; realistic "corbelling" below
the cap enhances the brick effect. A rain capspark
arrestor completes the installation.
We're often asked what happens if the chimney is damaged after
installation. One builder wanted to know what would happen to
the chimney if he ran into it with his backhoe. The answer is
that while we don't recommend bashing it with heavy equipment,
a cast chimney is much tougher than one made from bricks and
mortar. Minor damage can be easily field repaired with mortar
and touched up with stain.
One chimney to go, please.
The word is slowly getting around about our products, but for
now we still get some strange looks while we're on the road. A
few weeks ago, a truck with ladder racks was following us on a
state highway. The driver, who was talking on a cell phone,
craned his neck at our unusual cargo as he passed. Apparently
still unsure about what we were carrying, he stopped up ahead,
put down his phone, and got out of the truck for a better look.
I don't think we've heard from him yet, but we're expecting a
call any day now.Rick Rossiand his partner,Keith
Knickerbocker, are owners of
Chimneyworks, manufacturers of precast chimneys in Higganum,