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CG 5.1

June 1, 1996



Plywood shall be selected and installed in accordance with specification CG 3.0. Plywood shall be AC Exterior Underlayment with plugged crossbands under the face meeting specifications of the American Plywood Association. All interior grades, including those with exterior glue, are not acceptable. Plywood marked "Exposure 1" is not acceptable.


The deck area must be clean and dry. New plywood does not require primer. Prime galvanized metal flashings with a light coat of Gacoflex E-5320 two component water based epoxy. If U-66 is to be carried onto masonry, concrete or painted surfaces, also prime with E-5320. E-5320 is mixed in equal parts to which 10 or 15% water should be added. It must be well mixed. Apply by brush or roller at the rate of one gallon per 300 square feet and allow at least an hour for drying before coating with U-66 series urethane. Do not apply E-5320 primer when temperature is below 40 degrees F. Use masking tape on vertical walls to terminate coating in a clean, sharp line. Note: Only the final coat of urethane is carried onto the masking tape. Tape must be removed while the coating is still wet.


Gacoflex U-66 urethanes are two component, 1:1 ratio elastomers. Part A is pigmented and should be stirred prior to mixing with an equal volume of Part B. Best results are obtained by pouring a measured amount of Part B into a plastic container and mixing in an equal amount of Part A. This mixture must be stirred thoroughly with an electric drill and stirring paddle. Scrape sides of container often while mixing to insure there are no portions left unmixed. Small mixtures (under two gallons) can be mixed by hand, but must be well mixed. The pot life is about 1 hour. Do not use U-66 when ambient temperature is above 80 or below 40 degrees F.. If graininess is observed in either Part A or Part B, materials should be warmed prior to mixing as per label instructions, U-66 Part A.


It is helpful to prepare the plywood joints by sanding with a 9 inch rotary sander-grinder with a 24 grit sanding disc. This will level minor changes between sheets and remove slivers and burrs. Do not over-grind cutting ruts or troughs in the plywood. Apply a light coat of spackle to all joints, metal edges, and rough spots. Use a spackle or putty knife. Make spackle by adding a small amount of Patch-All powder to already-mixed U-66 (about 1/2 pint powder by volume to 1 pint of U-66 will be enough for about 100 SF of deck area). Spackle should be similar to a runny cake batter and runny enough to "wet" the plywood. Let this spackle set for about 1/4 hour but not more than 1 1/2 hours. Apply Gacoflex 66B tape to all joints, cracks and changes of plane. Premix a small amount of U-66 urethane as noted above. Thinning this mixture about 5 to 10% with T-5116 Thinner will make taping easier. By brush or roller, apply a five to nine inch wide stripe along all joints to be taped. While this is still tacky, unroll the tape into the coating and apply a heavy coat of liquid material over the tape, smoothing out wrinkles or fish-mouths. Stretching the tape very slightly while installing will help it lay flat.


Base cast can be installed after coated tape has set about 1/2 hour. Apply by roller an overall coat of U-66 urethane, using one gallon per 100 square feet. Be careful not to move the tape when rolling over it. Allow to dry 36 to 48 hours until hard.


Before applying second coat, it is helpful to lightly sand the surface to feather edges of tape and smooth any remaining rough areas. If you sand through the base coat you must re-establish a coat of U-66 urethane at that point and allow to cure. Apply second coat of urethane at the rate of one gallon per 125 square fast. Hand broadcast nut-shell granule into the wet coating to completely and uniformly cover surface. Approximately five pounds of granule are required for each 100 square feet. Coat and sprinkle small areas at a time, taking care not to overlap coating and granule at edges. When texture coat is dry enough to walk on (usually 24 to 36 hours), sweep away loose granule.


Apply third coat of U-66 in desired final color over granule at the rate of one gallon per 75 square feet. To minimize roller marks, try to roll this coat in two directions at 90 degree angle to each other, but always finish by rolling in the same direction


After final coat, allow at least 48 hours drying time before deck is put into use. In cool temperatures, a longer drying time will be required.


U-66 urethane coating cures rapidly and the cleaning of roller covers and brushes is usually impractical. Use T-5116 thinner for cleanup of hands and for thinning of material when an extension of pot life is required. Do not thin more than 10 % (less than a pint per gallon).

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