USG CastingFireplaceSurrounds User Manual
Gypsum Cements
A Guide for Market Planning,
Production, and Installation
Casting
Fireplace
Surrounds
With over 100 years of experience as a manufacturer of building materials,
United States Gypsum Company has a proven record of innovation and suc-
cess in developing new products that have become industry standards. We
specialize in the manufacture of wallboard systems, ceiling panel systems,
building products distribution, flooring products and systems and a wide
variety of plasters and gypsum cements for industrial and commercial
applications.
Photo credit: Buffalo Plastering and Architectural Casting,Buffalo, NY
Overview
Cast fireplace surrounds have become increasingly popular,
including those made from gypsum cements, foamed polyurethanes and Portland cement materials.
This manual is a guide to the use of gypsum cements in
manufacturing decorative fireplace surrounds. Because there
are so many variations of design, finish, and placement relative
to the firebox, this manual addresses the factors affecting the
finished piece when it is installed.
Review this information, making the basic decisions about
target markets, designs, raw materials, and output before
deciding how to create the surrounds. Although similar to
other ornamental gypsum cement markets, some factors
differentiate this market, including the safety issues of creating
a product used in high-temperature environments.
The information provided here will help you create highquality fireplace surrounds that meet performance expectations.
Pages
Planning
4
Firebox and Insert Knowledge
Building Code Considerations
Production
10
Getting Started Fiber Reinforcement
Design Considerations Manufacturing
Mold Materials Process Flow
Raw Materials
Installation
23
Safety
Support
24
Appendix Technical Service
Glossary 800 USG.4YOU
References
Web Site
www.usg.com
Answering the following questions about market planning
before you start the manufacturing process is critical to minimizing
production planning mistakes.
Will products fall within the Is the business primarily intended to be a low volume/high profit product offering, or a high volume/low profit
high end or low end of the market? offering?
What is the look of the product? Will the surrounds be aggregated, smooth, paint-grade,textured, or integrally colored?
What are daily production and shipping Seventy-five units per day is considered extremely high production. Daily output depends on inventory ability,
output expectations? production techniques, drying capacity of daily production, and installation arrangements.
Will you maintain inventory, or use JIT production is not always matched to daily production due to the need to fully dry the parts.
JIT production to meet demands?
Will you offer custom products only,a standard Mold type, mold material, and subsequent costs are affected by this decision.
product offering, or a combination?
Are you willing to produce interior products only? Gypsum cements for fireplace ornamentation are not to be used outside, regardless of coatings or treatment.
Are you willing to define and enforce Quality control does not end with the fabrication of the fireplace surround in the shop—installation
installation recommendations? recommendations must be met to ensure product safety.
What type of warranty will you offer? Your warranty should take into account your installation techniques and the type of firebox with which your
product will be used.
Planning
4 Casting Fireplace Surrounds
Due to the wide variety of fireplace inserts that are replacing traditional
masonry fireplaces, it is important to understand how the inserts’
temperature profiles can affect cast fireplace surrounds. There is
no comprehensive public source for technical information (mainly
thermal mapping and the impact on surrounding areas) that is so
crucial to the design, style, and formulation of fireplace surrounds,
and yet ignorance of these issues can be life-threatening. Fireplace
inserts should be UL-rated since there is a life-safety issue. Since
it is impossible to know the heat-related effects for all potential
combinations of surrounds, fireboxes, and inserts, we strongly
recommend that you contact insert manufacturers for thermal profile
information for their products.
Fireplace Circulating Firebox A fireplace with multiple-wall construction around the fire chamber that permits air to circulate between the walls,
Insert Types become heated, and enter the house directly or via short ducts.This firebox typically uses a blower kit to assist in
air circulation.
Direct Vent An appliance that draws combustion air from outdoors and exhausts its combustion products to the outdoors,
eliminating the need for a standard chimney system. The glass panel in direct vent units keeps the combustion
system sealed from the home, maintaining high efficiency and indoor air quality.
Gas Fireplace Insert A gas appliance designed for installation within an existing fireplace. Usually this consists of gas logs within a metal
enclosure surrounding the logs and covering the space between the insert and the fireplace opening.
Mechanical A firebox that vents combustion by-products horizontally through the wall with an electric fan. This configuration
Sidewall Vent
is commonly referred to as direct vent, but termination conditions differ.
Top-Vent A vented appliance that is primarily aesthetic, with lower heat efficiency than other types of fireboxes.Top-vent
inserts include standard masonry chimneys and non-masonry flues placed above the firebox.
Vent-Free or Ventless A gas appliance with no need for a flue. Although these units offer high efficiency, some areas may not permit their
use. Review local building codes before installation.
For clarification, a zero-clearance fireplace is any firebox with associated ornamentation directly adjacent to it
without clearance or setbacks.
Firebox and Insert Knowledge
5 Casting Fireplace Surrounds
In most cases, building codes leave the final installation and
configuration up to the general contractor or installer. Building
codes may not be clear regarding installation procedures; some
may not even address gypsum cement fireplace surrounds and
how heat can affect them.
However,there is a definite trend toward the development of specifications as part of building codes. Therefore
it is important for you to understand that you must periodically check building codes in relevant market areas,
since it is easier to modify your products as codes are developed than to have codes adopted and enforced
without your knowledge.
Code requirements may address flame spread, smoke contribution, structural considerations,and setback
distances of the surrounds from the firebox. All products used in fireplaces should conform to your local and
state building code regulations, along with the firebox manufacturers’ recommendations regarding placement
and installation of surrounds.
Code documents in your geographic region will include one or more of the following:
– International Building Code (IBC)
– International Residential Code (IRC)
– Uniform Building Code (UBC)
– National Building Code (NBC)
– Southern Building Code (SBC)
– Local Building Code
There are also other relevant documents to be aware of, such as National Fire Protection Association (NFPA)
information.
While the gypsum cement products used for fireplace surrounds are considered noncombustible by various
building codes, gypsum cements will deteriorate when exposed to high temperatures for extended periods. For
this reason we recommend, when possible, that setbacks for the fireplace surrounds and mantels follow code
recommendations for combustible materials to minimize the effects of prolonged heat exposure to the surround.
Since there are many types of fireboxes and inserts, follow the manufacturers’ requirements along with the
recommended building codes. While it is possible for gypsum cement fireplace surrounds to be placed closer
to the firebox than a surround made from combustible material, it is essential to understand the heat effects of
specific fireboxes and inserts on the gypsum cement fireplace surrounds you manufacture. Understanding this
will allow you to match your surround designs with thermal profiles of specific fireboxes and inserts.
Planning
Building Code Considerations
6 Casting Fireplace Surrounds
The following diagrams help illustrate the relationship of combustible materials to the firebox opening:
Minimum Mantel Vertical Clearances
There are minimums for clearances for combustible mantel height above a fireplace. NFPA codes for minimum
clearances are as follows:
Reference Mantel Shelf or Reference Mantel from Top
Breast Plate Depth of Combustion Chamber
a 10 A 19
b 8 B 17
c 6 C 15
d 4 D 13
e 2 E 11
7 Casting Fireplace Surrounds
a
b
c
d
A
B
C
D
e
E
louvered top assembly
top of combustion chamber
bottom of
top door trim
fireplace
Minimum Mantel There are minimum clearances for combustible mantel width beside a fireplace. NFPA codes for minimum
Horizontal Clearances clearances are as follows:
Mantel Leg from Side Opening
Mantel Leg Depth
Ref. Mantel Leg Depth Reference Mantel Leg from
Side of Opening
j10 J 11.5
i8 I 9.5
h6 H 7.5
g4 G 5.5
f2 F 3.5
Planning
Building Code Considerations
8 Casting Fireplace Surrounds
J
I
H
G
F
side of combustion chamber
f
g
h
surround face
mantel leg
i
j
Minimum Mantel Flat Trim
Horizontal Clearances
– If the trim projects from the facing less than 1.5 inches (K), it must start at least 6 inches (L)
from the fireplace opening.
– If the trim projects from the facing more than 1.5 inches (K), it must start at least 12 inches (M)
from the fireplace opening.
9 Casting Fireplace Surrounds
L
6" min.
M
12" min.
1
1
/2" min.
6" min.
K
L
L
6" min.
To get going, start simply and think about this four-step process:
Mold Making The actual fabrication process begins with making the mold. Mold quality will directly affect the quality of the fin-
ished piece, so select a mold maker whose skills complement your desired market positioning. Many fireplace sur-
round fabricators have in-house expertise in mold-making.
Raw Material The only gypsum cement products that USG endorses for this application are HYDROCAL®FGR, ENDURACAST
™
Selection Gypsum Matrix, or other custom-formulated alpha gypsum cements manufactured by USG for fireplace surround
production. (See Raw Materials.) Your USG sales representative will help you select the material to match your
plans. You will need to have fiber reinforcement such as glass fiber or glass matting, mold release materials, a
clean water source, safety glasses, dust masks and gloves.Keep all gypsum cements and aggregates dry and
above freezing temperatures before use.
Fabrication Method Start by using a hand-layup method of filling the molds to get to know the gypsum cement product’s setting time,
expansion, pigmentation and aggregation capabilities, and how easy it is to work with. In this way you will also gain
experience with how easily the cast parts remove from the mold, the quality of the mold details, and how easily the
mold is cleaned and serviced. Properly supporting the cast surround immediately after removal from the mold is
also important, and there are various methods to ensure dimensional stability during drying.The time required
to fully dry the parts is also important, due to its effect on daily output. A surround is not ready to finish and install
until it is fully dried of all free moisture.
Waste Management Preparations for disposal of wooden pallets, paper bags, and wash-out and waste water should be part of the early
stages of business planning, along with dust-control procedures. Gypsum cements are environmentally friendly,
but cleaning molds and mixing the gypsum cement products produces water and gypsum waste that is messy if
not properly managed. Properly designed shops take waste-control procedures into account in the production
flow process, and good planning will minimize waste from the operation.
Production
Getting Started
10 Casting Fireplace Surrounds
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