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> Installed weight of plaster
Q: What is the installed weight of portland cement plaster?
 A:
This question comes up in both new and repair construction. Designers
need to know how much weight the stucco adds to the wall so that
they can be sure the structural system provides adequate support.
In new construction, the structural system usually has more than
enough strength to support installed plaster. In buildings that
are being updated or retrofitted, however, stucco may be placed
over existing construction. Especially in this case, designers should
verify that the added weight of the new stucco will not exceed the
structure’s ability to support it along with whatever other
materials remain in place.
Concrete or masonry walls generally have sufficient structural
strength to support the additional weight. In wood frame construction,
support members (studs) should be checked to ensure they can carry
the extra load.
On wood framing, three-coat plaster is typically installed over
metal lath to a 7/8 in. nominal thickness. A typical plaster mixture
weighs about 142 pounds per cubic foot, roughly the same as mortar,
and this amount of material would cover about 13.7 sq ft at 7/8
in. thick. The metal lath may add a small additional amount of weight,
so the end result is that three-coat stucco weighs about 10.4 lbs
per sq ft (psf) installed.
For more information about the unit weight of plaster or installed
weight, see Tables 1a and 1b on p.6 of PCA’s Portland
Cement Plaster/Stucco Manual, Fifth Edition (EB049.05).
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