USG Casting Fireplace Surrounds - Manual (Page 23)

23 Casting Fireplace Surrounds
Installation
Safety
When developing the final design of the fireplace ornamentation,
think about the best installation method. If internal supports and
built-in fastener attachments are part of the product design, they
will need to be included when the parts are made. Since these
products must be attached to existing structural members in the
building, you’ll need to consider do-it-yourself installation or
using a trained crew. Because of the many design possibilities and
corresponding installation considerations, we cannot provide
specific placement and attachment recommendations. However, there
are a few general guidelines about gypsum products:
– Parts made from gypsum cements are not load-bearing. The side pieces cannot be the mantel’s sole support.
We recommend that the cross-section (mantel) not be solid-cast so that some type of support (either wood or metal)
can be placed in the hollow back of the mantel. A wood support cast into the part must be sealed to resist moisture,
and metal supports should be epoxy-coated. Anchor supports to the structure of the building to minimize both move-
ment from thermal forces (expansion and contraction) and the risk of cracking. The legs of the surround also need
to be anchored to the structure, but typically are not exposed to the same temperatures as the mantel. Make sure the
entire surround is fastened securely to the structure of the building for life-safety reasons.
– Heavy parts make the installation more complicated, because you’ll need to use large fasteners.
– You must use mechanical attachment to the building structure. If using adhesives in conjunction with mechanical
anchoring, ensure that the adhesive is not flammable in the cured state and has a service temperature above the
maximum heat to which the fireplace surround is exposed. Do not use adhesive as your only means of attachment.
– Mechanical fasteners should have a large-diameter washer such as a plaster washer at the head when the gypsum
cement is the bearing surface. When the bearing surface is wood or metal, any conventional fasteners except
plastic may be used.
– The use of adhesives to bond brackets or other attachment devices to the finished gypsum cement part is not
recommended unless endorsed by the adhesive manufacturer.
Repairs After the installation, repairs to the surround may be needed because of the holes made from fastening the surround
to the building structure. Typically these holes are from a drill and can be easily patched using joint compound, spackle,
or caulk. In some cases, you may want to bring a small amount of the gypsum cement you used to produce the sur-
round, and mix a small amount by hand to use as a repair material.
There may be some gaps or uneven surfaces around the perimeter of the surround after it is installed. Seal these
gaps with a high-temperature caulk or similar material.
Any repair or finishing material used should be capable of withstanding the temperature environment created
when the firebox is in use.