How to Install Stucco

Building a stucco wall. For centuries, stucco has proven to be one of the most
enduring, versatile and weather-resistant exterior wall
finishes available…and with its variety of colors and textures, stucco continues to be one of the most
popular wall systems. Stucco can be applied over standard, wood
frame walls in a three-coat process and over masonry
and poured concrete walls in a two-coat application. Before
starting your project, check local building codes for wall
assembly and moisture barrier requirements in your area. Weather-resistant stucco
walls require the use of two layers of grade D waterproof building paper over
the wall sheeting including plywood, OSB, exterior
gypsum board and concrete board, before the application
of the base coat stucco. When attaching the waterproof building
paper, vertical seams should be overlapped by 6
inches or more and horizontal seams should be overlapped
by 4 inches, in shingle fashion. The building paper
should also extend 16 inches around all corners. Once the water
resistant building paper is in place, all trim accessories should be installed. Trim accessories can be cut to size
using metal snips. Cut edges are often very sharp, so always
wear gloves when working with these materials. a weep screed is a typical excess will
be required by code. Weep screeds are installed along the
bottom edges to allow any water that has entered the wall to escape. Casing beads should be installed to neatly
terminate stucco at the end of the wall. Casing beads also act as a guide to help
maintain a consistent stucco thickness. casing beads, for a three coats system,
should be three quarters of an inch thick. Casing beads for use in a two-coat
system over masonry or concrete should be 1/2 inch thick. Then, galvanized expanded metal lath or 1 inch
woven wire stucco netting is installed over the entire surface,
overlapping by one inch on the horizontal seams and two inches on the vertical seams.
Galvanized nails or staples should be used every six inches, both vertically and horizontally. Make sure
that the nails or staples penetrate the studs a minimum of one
inch. The lath or stucco netting should also extend 16 inches around all corners. If the base coat
stucco is applied to a clean unpainted concrete or masonry surface,
waterproof building paper and metal lath are not required. Then, control joints should be placed to create
wall panels no larger than 144 square feet, keeping the panels as square as possible.
Stucco will shrink as it hardens and cures. Control joints help reduce the potential
for shrinkage cracking. Expansion joints are required anywhere
there are existing wall expansion joints and at inside corners and changes in
substrate. Expansion joints are designed to allow
for the expansion and contraction of the stucco wall panels with changes in temperature. Corner trim
should be used on all outside edges, to protect the exposed
stucco and to provide clean finished lines. Now that the substrate is
properly prepared, it is ready for the base coat stucco
application. QUIKRETE Base Coat Stucco and QUIKRETE Base Coat Stucco with Water-Stop are recommended for use in a traditional three coats system over
wood sheeting and as the base for a two coat application
over masonry or concrete. These pre-blended stuccos are
extremely workable for hand applied stucco applications and have the high bond strength required
for a successful project. Mix the base coat stucco to a workable
consistency. The proper consistency is achieved when
the stucco will hang on a trowel held at a 90 degree angle. Stucco that
is mixed too wet will sag. Stucco that is mixed too dry will
not adhere properly to the metal lath. One bag of 80 pound base coat stucco
will cover about twenty seven square feet at three-eighths of an inch thick. Using a
square trowel, held at a 45 degree angle, apply the base
coat stucco using firm trowel pressure to force the stucco
into the lath. Work from the bottom of the wall up and
apply at a thickness of about three-eighths of an inch over the
entire area. Then, using a straight edge or darby, screed the
stucco to a uniform depth of 3/8 of an inch thick. Once the stucco has become thumb print hard,
scratch horizontal grooves, 1/8 of an inch deep, into the base coat, across the entire
area with a raking tool. This is why this step is commonly
referred to as the scratch coat. Allow the scratch coat to cure for 24 to
48 hours. Keep the surface of the stucco damp with
a fine water mist. This step will help reduce shrinkage
cracking, especially in hot dry conditions. Now, mix and apply another 3/8 inch layer of base coat stucco directly to the
scratch coat. This step is called the brown coat. Using
a straight board or darby, screed the brown coat surface to a true
even 3/8 inch thickness. Fill any surface boards with
additional base coat. The total combined base coat depth
should be three-quarters of an inch thick. As soon as the strucco has lost its
sheen, float the surface uniformly. Then, cure the base coat with a fine water
mist for 24 to 48 hours. For two-coat applications over masonry
block walls and poured concrete walls, the scratch coat step is eliminated from
the process. Simply dampen the wall. Apply the brown
coat. Then, screed and float the surface to a uniform 3/8 inch thickness. Now that the base coat is complete, QUIKRETE Finish Coat Stucco can be used
to provide numerous decorative color and texture options for your stucco wall. Finish Coat Stucco is available in both
white and gray formulations and can be combined with more than 20
standard QUIKRETE Stucco & Mortar colors. Popular textures, such as heavy lace, light
lace, dash, sand float and smooth finishes are
easy to achieve with a little practice. Working from the bottom of the wall to
the top, apply a consistent 1/8 inch thick coating of Finish Coat
Stucco. Then, use a whisk brush to lightly dash
finish coat stucco onto the wall. Then, use a trowel to knock down and flatten the stucco. If you prefer a heavier texture, first
spread the finish coat stucco in a thin application to achieve good color
coverage, and then, double back with a heavier
uneven application. Once the heavy coat begins to harden
knock the finish down with a trowel, creating a heavy lace finish. If a
smooth finish is your preference, simply use a trowel or sponge float in a
circular motion. It is important to complete the entire
wall in one application. This will help limit any color
inconsistencies from batch to batch. Then, keep the surface damp for several
days by applying a fine water mist.

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