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COATING
METAL ROOFS WITH EPDM LIQUID RUBBER® |
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F9981
White, F9999 Black, F9988 Gray |
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Liquid Rubber
may be applied on roof decks, gutters, structural steel, air
conditioner enclosures, cooling towers, galvanized steel,
unit heater flues, smoke stacks and chimneys, fiberglass and
non porous masonry surfaces. |
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Surface preparation |
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All surfaces to be coated should be clean
and dry. Remove peeling paint and brittle caulking. Heavy
build-ups of asphalt roof cement should also be removed.
Tighten any loose fasteners and replace those that are
severely corroded. Repair or replace roof panels damaged by
storms. Remove heavy rust with abrasive discs or wire
brushes. Power-wash all surfaces to be coated and allow to
thoroughly dry. Caulk all gaps wider than 1/16 inch that are
not expansion and contraction slip surfaces. |
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Treating rusted areas
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It is recommended that a corrosion
inhibitive primer first be applied to areas where severe
rusting has occurred. Liquid Rubber does not contain any
corrosion inhibiting pigments but it is such an effective
moisture barrier that it may be directly applied over light
rust without a primer. |
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Going over existing coatings |
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[1] Original mill
finish |
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When the original coating is still
adhering tightly, it can be top coated directly with Liquid
Rubber. Corrosion inhibitive primer should still be used on
severely corroded areas. |
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[2] Alkyd paints |
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Aged alkyd paints that were applied over
the original mill finish should be checked for adhesion. If
coating is brittle and can be scraped off easily, it must be
removed before Liquid Rubber can be applied. If removal can
be accomplished with high- pressure water spray, that should
be the method of choice. If removal is spotty, the roof
should be allowed to weather another year before removal is
again attempted. Brittle alkyd paint will continue to lose
adhesion over time and will result in predictable failure if
not removed. |
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[3] Asphalt based
coatings |
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Liquid Rubber should not be applied
directly over asphalt based coatings. Water based acrylic
elastomeric coatings may be used as intermediate coats, on
sloped roofs only, before applying Liquid Rubber. Asphalts should be considered
as being unstable materials and are excluded from warranty
coverage by Pro Guard Coatings. Caution-Latex house paints
cannot be substituted in place of the acrylic elastomeric
coating. |
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[4] Acrylic
elastomeric coatings |
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Liquid Rubber bonds very well to these
coatings. Some of the earlier acrylic elastomeric
formulations were prone to the development of under film
corrosion. There usually is little visual evidence of this
on the surface of the acrylic so small sections of coating
must be removed from different parts of the roof to
determine whether the condition exists and how severe it is.
A visual inspection of the underside of the roof panels can
reveal total penetration in the most severe cases. The
decision of whether to apply Liquid Rubber over an area with
severe under film corrosion becomes an economic one. The
recommendation should be to replace the corroded panels.
However, if this is not an economically viable solution and
removal of the coating is equally impractical, then
application of the Liquid Rubber may be justified as being
the best of the available alternatives. No warranty would
apply in such a case. |
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Application of Liquid
Rubber |
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Airless or Air Atomized spraying is the
only feasible application method for corrugated or standing
seam roofs. Airless equipment needs only one hose from pump
to gun but must generate 3500-4000psi and is limited in the
length of hose that can be used because of high-pressure
drops. Air atomized equipment requires two hoses to the gun
making it more cumbersome to maneuver plus the addition of a
compressor. |
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Equipment capable of
spraying Liquid Rubber |
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Pump Model |
Max. Pressure |
Fluid Flow |
Hose ID |
Max. Hose Length |
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Graco GH733 |
3500 psi |
3.0 gpm |
1/2 inch |
150 feet |
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Graco
GH3640 Roof Rig |
36000psi |
3.8 gpm |
1/2 inch |
150 feet |
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Gun |
Should be rated for spraying
mastics. A 30-40 inch tip extension is
recommended. |
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Tip Size |
.017 to .021 with a 12 inch fan
width |
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Note: Do not
use a "whip" between hose and gun. This reduces
flow and pressure which results in poor atomization. |
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Liquid Rubber will produce greater line
drops and spray with a narrower fan than most other coatings.
Some solvent (Xylene or mineral spirits) must be used to thin
the product to make it spray easier. This dilution should
not exceed 5 quarts solvent per 5 gallon pail. The
recommended procedure is to spray apply and roll back with a
short nap roller to obtain an even film and complete surface
coverage. Application should be at rate of 40-45 square feet
per gallon. This will produce a 20 mil dry film. The
chemical and physical properties of Liquid Rubber make it
possible to achieve a 20 mil dry film on sloped or vertical
surfaces with one evenly applied coat. Spray-on
followed by rolling where surface configuration permits will
produce an even film. Roller marks will level out in a few
minutes. |
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Fasteners |
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Caulking around fasteners is usually not
necessary. The physical properties of the EPDM rubber
(Liquid Rubber) will produce a longer lasting seal around
fasteners than caulks will because the latter will embrittle
with age causing loss of adhesion and cracking. It is good
practice to brush the rubber into the fasteners after spray
application to ensure complete coverage. This procedure will
still be less time consuming than caulking. |
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Fabric reinforcing of seams
and overlaps |
Tight overlaps and standing seam joints
do not need to be reinforced.
Overlaps with gaps greater than 1/16 inch and corroded edges
should receive fabric reinforcing. Apply a light coat of
Liquid Rubber, center the fabric on the overlap and roll it
out taking care not to create wrinkles; press fabric down
with squeegee or wide spatula; spray apply a full coat of
Liquid Rubber to seal top surface of fabric and roll back
over to ensure coverage. |
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Over spray |
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If over spray lands on cars, it can be
easily removed with Mineral Spirits within 24 hours.
Thereafter, stronger solvents such as Xylene will be
effective in removing the rubber but may dull some finishes.
Black, one-foot square test panels should be placed in
various parts of the parking area as evidence of over spray
in the event later claims are made. |
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Flushing Spray
equipment |
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Three separate flushes with Xylene are
recommended. (Save this solvent for future use). When
the last of the Liquid Rubber is sucked from the pail, add
several gallons of Xylene to pail to purge material from
line and onto roof. Remove gun from the hose and place end
of hose in same bucket as pump suction. Reduce pump delivery
pressure and allow solvent to recirculate for five minutes.
Remove suction tube from bucket and purge line. Starting
with clean solvent or the final flush from a previous
cleaning, repeat the procedure two more times. The gun
can be reattached during the final flush for cleaning.
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Pail handling and disposal |
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Pour material from newly mixed pail into
the one from which the pump is sucking. Scrape the sides of
the just emptied pail into the next one to be mixed. Only a
thin film of material should remain. When this procedure is
used, the pails can be collapsed and placed in a trash
dumpster or taken to a metal recycler. |
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Rain showers or freezing
temperatures |
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Unexpected rain showers after application
may affect the surface appearance but will not wash material
off roof. Temperature drops below freezing will arrest the
cure but will not damage Liquid Rubber. The cure reaction
will resume again whenever adequate temperature returns.
Click here to
Order EPDM Liquid Rubber. |
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On some
materials, such as EPDM rubber sheets, some swelling may
occur due to solvent absorptions after applying
EPDM Liquid Rubber®. This
is normal. This swelling will recover with time and heat. In
80° F or so, allow 7 to 14 days to recover. In colder
temperatures, recovering will take several weeks, as much as
6 to 8 weeks in 60° F. |
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The
information presented herein is furnished free of charge and
is based on technical data that Pro Guard believes to be
reliable. It is intended for use by persons having technical
skill and is at their own discretion and risk. Since
conditions of use are outside our control we make no
warranties, express or implied, and assume no liability in
connection with any use of this information. Nothing herein
is to be taken as a license to operate or a recommendation
to infringe any patents.
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