MIL-HDBK-1011/1
9.5
Plastering Systems
General. A portland cement-lime mix is corrosive to metal lath in
9.5.1
tropical environments. To reduce plaster and stucco cracking, which
contributes to moisture and condensation infiltration delete the lime base and
substitute a liquid plasticizing agent with the principal ingredient of a
resin compound. The result produces a material with greater resistance to
most climatic effects in the tropical zone. Include sufficient control joints
to minimize structure-related cracking.
9.5.2
Exterior Insulation and Finish Systems. These systems, consisting
of an insulation board with integral scrim and synthetic plaster finish, are
sold as a "complete system" by numerous firms. They have the advantage of
providing a "plaster" exterior with integral insulation and can be applied to
existing concrete and masonry surfaces as well as to wood or metal stud
systems in new construction.
Their disadvantage is that they can be installed only by
manufacturer-approved installers. This may be an impossible criteria to meet
in the tropics, particularly in remote areas. Additionally, damage to a large
area of the surface, say in an accident involving a forklift or motor vehicle,
will require repair with original materials and approved installer to maintain
the manufacturer's warranty on thermal and moisture protection.
Use these materials as a combined exterior finish with built-in
layered insulation board, thereby achieving two separate functions: providing
the finish plus insulating, which contribute to an energy-efficient building.
Application can be over any substrate, both new and existing surfaces.
9.5.3
Special Considerations. If surface is to be painted, do not use
coral aggregate in the plaster system. If no option is available, use a
sodium silicate system for stabilization.
9.6
Acoustical Tile and Metal Ceiling Suspension Systems. Ceiling
suspension main runners and cross runners, including wall channels,
miscellaneous moldings and accessories, are an aluminum alloy and finished as
applicable, except where fire-rated installation is a requirement. In fire-
rated areas, a concealed grid system with galvanized steel, factory finished
with baked enamel, is recommended.
9.6.1
Hangar Wire. Where the hanger wires are located in attic areas
vented to the outside in a salt spray environment, use stainless steel or
copper-bearing alloy wires. Do not vent attic areas above air-conditioned
spaces where cold water lines or A/C ducts are located. Ensure that these
areas are air conditioned to preclude condensation problems.
9.6.2
Installation.
Dissimilar metal installation must include standard
preventive measures against electrolytic corrosion. Ensure that all aluminum
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