GW 2-2

Priming

Gaco Western elastomeric coatings frequently require a primer. The preferred primer varies with the substrate and conditions as described below. Guide specifications explain specific primer requirements. Product Data Sheets contain application instructions and precautions for each product.

Gaco Western has many different types of specifications for the roofing and waterproofing industry. As a general guide the following methods of priming the various substrates are recommended.

A. CONCRETE

1. Sealing Exterior Concrete: Most concrete has surface porosity that is caused by several factors; among them water content, drying rate, aggregate type, and trowleling action. When elastomeric coatings are applied over concrete, there is risk that blisters will form from out-gassing through surface pores. This risk is virtually eliminated by the use of a primer-sealer system.

   The GacoFlex primer-sealer system should be applied on all light weight structural concrete and dense aggregate structural concrete which might be exposed to sunlight during coating application.

   Prime entire deck surface and all vertical or sloping surfaces of curbs, cants, parapets, etc. which are to receive roof coatings with one coat of GacoFlex U-5677 Sealer by roller or spray. The coverage is about 1/3 gallon per 100 square feet (1.25 L / 9.3 m²). Allow to dry a minimum of one hour and no more than 72 hours before applying GacoFlex E-5320 Epoxy Primer.

   Apply one coat of GacoFlex E-5320 at the rate of 1/2 gallon per 100 square feet (1.89 L / 9.3 m²). Most efficient sealing is obtained when E-5320 is applied late in the day when temperatures are decreasing. GacoFlex E-5320 is a two-component water based epoxy and must be thoroughly mixed.

   The pot life is 1 1/2 hours at 75°F (24°C). This can be extended to two hours by thinning with water to achieve the original consistency. Pot life at 55° (13°C) is double, but at 100°F (38°C) it is reduced to forty five minutes. GacoFlex E-5320 can be applied to surfaces with temperatures up to 110°F. The normal minimum surface temperatures for application of E-5320 is 55°F (13°C).

   Alternative Concrete Primer/Sealer: Apply one coat of GacoFlex E-5511 to all surfaces to receive the fluid applied waterproofing, except areas previously caulked, flashed or fabric reinforced. Apply at a rate of one gallon per 150 sq. ft. (3.78 L / 13.9 m²) and allow to cure at least 6 hours, but no more than 3 days before applying the basecoat.

   Surface temperature is more important than air temperature. When the surface is cooler than 55°F (13°C) DO NOT apply primer sealer system unless special instructions are secured from Gaco Western.

   Cure should be verified as follows: When the daily maximum surface temperature is at or near its peak, apply regular thinner to a sealed surface. Let the area soak for three to five minutes, then scrape with a dull knife or spatula. Scrape from a dry area into the wet area. If softening in the wet area is noted, additional cure is needed. Softening in the solvented area is most easily detected by a change in the sound of the knife as it passes from the dry area to the wet area.

2. Interior Concrete: On dense aggregate concrete used for interior construction or exterior areas which are not exposed to sunlight, GacoFlex U-5677 and E-5320 can be used.

   Alternative Concrete Primer/Sealer: Gaco Western's Zero VOC 100% solids, two component epoxy E-5511 primer/sealer.

   Prime entire deck surface and all vertical or sloping surfaces of curbs, cents, parapets, etc., which are to receive coatings, with one liberal coat of primer applied by roller or spray. Sufficient quantity shall be used to flow into all remaining holes and cracks in the surface of the slab. Allow minimum drying time of two hours. The coverage rate is 1/2 gallon of primer per 100 sq. ft. (3.78 L / 9.3 m²).

3. Concrete Block: To fill and prime concrete block, use GacoFlex E-5320, a two-component water based epoxy.

Mix one volume of Component A with one volume of Component B. Mix thoroughly. Power mixing is recommended for quantities over two gallons (7.57 L). The pot life is 1 1/2 hours at 75°F (24°C). This can be extended to 2 hours by thinning with water to achieve the original consistency. Pot life at 55° (13°C) is doubled, but at 100°F (38°C) it is reduced to 45 minutes. Use long nap (1" to 1¼") (2.54 cm to 3.18 cm) rollers when filling porous concrete. If blow holes form as the primer dries, make a second pass with a relatively dry roller. Allow five to ten minutes between passes. Hypalon and polyurethane coatings can be applied over E-5320 as soon as it is thoroughly set. This degree of dryness is normally achieved in two to three hours. Neoprene should not be applied directly to E-5320 until it has cured over night.

B. WOOD

Gaco Western neoprene and polyurethane coatings are self priming when applied to new wood construction. Soiled or weather checked wood requires that the first coat be thinned with the appropriate thinner. This procedure provides optimum adhesion and can also be used on new, clean wood surfaces.

C. STEEL

GacoFlex E-5320 two-component epoxy primer may be brush or roller applied as mixed when the temperature is 65°F (18°C) or higher. For most applications and for spraying, it is desirable to reduce 10 to 20% with water. Coverage per gallon is 300 to 400 sq. ft. (3.78 L / 27.9 to 37.2 m²).

The minimum temperature for proper application and cure is 50°F (10°C). Approximately two hours dry after application is needed to develop resistance to rain. Allow eight hours cure time before overcoating with neoprene and two hours for Hypalon and polyurethane coatings.

Primed surfaces should be protected from dust and moisture prior to coating application.

Light dust deposits, which collect on the surface, may be removed with a clean, dry brush. Standing moisture may cause rust which must be removed and the surface reprimed.

D. NON-FERROUS METAL AND GALVANIZED STEEL

Use GacoFlex E-5320 primer applied by brush roller or spray as described in Section C.

NOTE : Galvanized Steel can have a process oil present which should be removed by solvent wiping prior to the application of primer.

E. POLYESTER LAMINATE, GLASS OR EPOXY

Gaco Western has 2 primers that perform extremely well on these substrates: E-5320 or E-5511. The coverage rate per gallon is 300-400 sq. ft. (27.9 to 37.2 m²). Because of its extended recoatability GacoFlex E-5320 is the primer of choice. Apply primers by brush, roller or spray. Allow the primers to dry before applying foam or coatings.

F. POLYURETHANE FOAM

While primer is not usually required before coating polyurethane foam, unusual conditions may demand special consideration. For specific recommendations consult with your Gaco Western Area Manager.

G. COATED SURFACES

Gaco Western has specifications for recoating existing foam and coating roofs, neoprene/Hypalon deck systems and polyurethane deck systems. These are located in their respective sections in the catalog.

As a rule any well adhered material that is sound may be recoated with the proper primer. GacoFlex U-5677 is usually used for all recoats except for existing silicone. Coverage rate is usually 1 gallon per 300 sq. ft. (3.78 L / 27.9 m²), drying is as described above.

If the existing coating is unknown it is best to apply a sample to determine compatibility. Contact Gaco Western for recommendations.