Gaco Roof Application Guide

Just some tips and tricks on applying GacoRoof. And maybe some Frequently Asked Questions. And a video or two. And flyers. Wow. This post really has it all, eh?

It is extremely important to get the roof clean and dry. First remove heavy deposits of dirt, leaves and other debris from the roof using broom or air broomer, then inspect the entire roof surface and flashings for any open seams, tears, cuts, etc. Repair these flaws so water is not blown in under membrane during the cleaning process. Pressure wash roof with water and allow to dry completely.


For general cleaning, apply GacoWash Concentrated Cleaner according to label instructions. On all single-ply membrane roofs, after application of cleaner, power scrub the roof surface until clean and then power wash to remove debris and continue rinsing until all suds are gone. 

Biological Control: Areas of algae, mildew or fungus on the roof membrane or the existing coating should be treated with a solution of 1 part household bleach and 3 parts water,

followed by a power washer rinse using clear water. Drying: After cleaning and rinsing the roof, ensure no dirt or debris is present. Allow surfaces to thoroughly dry to prevent blistering. Examine roof, paying particular attention to areas of physical damage to determine that residual water has in fact dried before applying coating. NOTE: Drying time depends on weather conditions such as temperature, humidity and air movement.

Bonds to Most Surfaces (including but not limited to):
  • Aged Asphalt*
  • Aged EPDM and TPO/CPA
  • Built-Up
  • Cap Sheet
  • Composite
  • Concrete
  • Fiberglass
  • Metal
  • Modified Bitumen
  • Torchdown
  • Most existing coatings
  • Sprayed Polyurethane Foam
  • Low-Pitched Roofs
  • Flat Roofs
  • Mobile Homes
  • RV’s & Campers

*Not for use on 3-tab asphalt or architectural shingles.

May require multiple coats to create a seamless membrane.

If the roof has been patched with any asphalt or black tar-like products within the last 12 months, applying a coat of GacoFlex E5320 2-Part Epoxy Primer/Filler may help prevent bleed-through staining on the final coats. GacoRoof will adhere to most surfaces without a primer; however, some substrates may require a primer for optimal adhesion. To verify adhesion, use the GacoRoof Adhesion Test Kit, which provides results in just 24 hours. If the test reflects poor adhesion, prime all surfaces with GacoFlex E5320 according to label directions.

A minimum of two coats are required; Recommended final film build is a minimum of 22 dry

Appl2mils. To help ensure complete coverage during application of the final coat, it is recommended to use a different GacoRoof color for the first coat to create a color contrast. Mix before application to ensure uniform color and consistency. Product should not be thinned.

Flat roofs (less than 1:12 pitch/5°): Use a solvent-resistant ¾” or 1” nap roller cover and depending on type of roof, dip roller directly into pail and apply, or pour product onto flat roof surface and roll out evenly, or for very smooth surfaces, pour out product and spread with an 1/8” notched squeegee then immediately back roll for a smooth, even finish.

Pitched roofs (greater than 1:12 pitch/5°): Use extreme caution when on a pitched roof. Follow all safety guidelines to avoid injury. Use a solvent-resistant ¾” or 1” nap roller cover, dip roller directly into pail, and apply. A roof pitch greater than 4:12/19° is not considered walkable; Additional reach equipment may be needed to properly apply the product safely and effectively.

Allow the first coat to dry for 3 to 12 hours. Apply second coat as soon as the first coat can be safely walked on. The coverage rate of GacoRoof is 100 sq. ft. per gallon in each coat on a smooth surface; coverage rate may decrease on textured surfaces, and more coating will likely be used on first coat than on additional coats. Smooth roofs can be completed in 2 coats, lightly textured surfaces often require 3 coats, and heavily textured surfaces may require 4 coats to achieve a final 22 dry mil film build.

Do not apply in temperatures below freezing, above 120°F (49°C) or if rain is expected within 2 hours. Do not walk on GacoRoof other than for periodic maintenance; for areas of light foot traffic, create a walking path by applying a coat of LiquidRoofTape according to label instructions.

Independent contractors who are utilizing an airless sprayer should consult our GacoRoof Silicone Spray Guide and Safety and Storage Guide.

Application tools and equipment can be cleaned with GacoFlex Silicone Solvent or 100% Pure Mineral Spirits. DO NOT USE WATER OR RECLAIMED SOLVENTS. Once a container of GacoRoof is opened, the curing process has started. Use the entire product on your project if possible. Allow any remaining product in the container to solidify and dispose of in the proper manner.

Roof structures may settle over time. A periodic inspection of your roof, which includes transition areas, flashing, vents and skylights, is recommended. Keep drains cleared at all times. Roofs become slippery when wet. Use extreme caution. Do not recoat GacoRoof with acrylic, urethane or Hypalon® coatings. Recoat cleaned GacoRoof only with more GacoRoof.

CAUTION: An old, neglected, or failing roof does not have the resilience to withstand the rigors of weather. GacoRoof may not be suitable for such a roof. If you are in doubt about the condition of your roof, consult a qualified roof inspector.


Frequently Asked Questions

I am unclear about the coverage rates for GacoRoof. The package and the brochure seem to have different rates. Why is this?
The confusion between the brochure and package is this: because TWO coats are required, the coverage for the COMPLETED project is 1 gallon per 50 square feet. (You can use this rate to figure out how many gallons you need to purchase).

The APPLICATION rate (the amount used to gauge the proper thickness when rolling the silicone coating onto your roof ), is 1 gallon per 100 square feet.

So, how much Acrylic roof coating do I need for the same job?
Acrylics typically require more than DOUBLE the amount of GacoRoof coating for the same roof project. For most acrylics, you need to apply one coat of sealant and/or primer, PLUS a base coat, PLUS one or two additional top coats at a rate of 1 gallon per 100 square feet. You’ll need 1 gallon of primer and 2-4 gallons of acrylic roof coating for every 100 feet. When you include accessory products, such as patch compound, fabric and sealer, the cost of an acrylic coating really adds up.

And don’t forget that the typical acrylic roof only lasts about 3-5 years before a recoat is required!

OK, so how does GacoRoof compare to acrylic roof coatings?

  1. GacoRoof has a 50-year limited warranty. GacoRoof will last as long as the substrate it is applied to. Acrylics, if they have a warranty at all, warranty only 3-5 years. One acrylic offers an 8-year warranty BUT you have to recoat every 3 years.
  2. GacoRoof can withstand PERMANENT ponding water. There are no acrylics that will stand up to the stress of permanent ponding water without bubbling or adhesive failure.
  3. GacoRoof can be applied in a wide temperature range (32-120 degrees F). Acrylics cannot be applied at temperatures below 55 degrees or above 90 degrees.
  4. All acrylics require a primer coat. GacoRoof does not require any primer, sealer or patch compound.
  5. GacoRoof does not require a recoat. Silicone is inert, and does not degrade or wear away. Acrylics require a recoat every 3-5 years.

Are you sure my roof does not need a primer coat? Do I need to prime metal flashing or other metal surfaces?
Metal flashing should either be primed with an exterior metal primer, or lightly sanded. Most other roof surfaces do not require a primer before applying GacoRoof. See the list of acceptable substrates below.

What substrates does GacoRoof adhere to?
GacoRoof adheres to a multitude of roof types. Suitable substrates include silicone, aged asphalt (not for use on 3-tab asphalt or architectural shingles), aged EPDM and TPO/CPA (may require GacoFlex E5320), built-up, cap sheet, composite, concrete, fiberglass, metal, modified bitumen, torchdown and sprayed polyurethane foam.

GacoRoof is perfect for Residential and Commercial buildings, as well as flat and low-pitched roofs, mobile homes, RV’s and campers.

What about EPDM & TPO Roofs?
GacoRoof may be applied to Aged EPDM and TPO roofs but may require the use of GacoFlex E5320 2-Part Epoxy Primer/Filler. To verify adhesion, use the GacoRoof AdhesionTestKit, which provides results in just 24 hours. If the test reflects poor adhesion, prime all surfaces with GacoFlex E5320 according to label directions. Call toll-free (866) 422-6489 for more information and specific recommendations.

Can GacoRoof be applied with a sprayer?
GacoRoof should not be sprayed because it is too thick for spray equipment. If GacoRoof is thinned with mineral spirits, it no longer meets the regulations for minimum V.O.C.’s (volatile organic compounds).

Does GacoRoof come in other colors?
GacoRoof is available in White, Gray, Green, Light Tan, Rustic, Medium Blue, Black, Brown and Red. GacoRoof White may be tinted Gray using GacoRoof Colorant, which can then be applied as the base or top coat.

What is skinning? What happens if I don’t use the entire pail right away and a skin forms?
Skinning is when the topmost layer of coating begins to cure in the pail. Silicone is moisture-cured, so high heat and humidity will cause the product to skin. If surface skins, remove skinned material from container. To minimize skinning over several days, pour a thin layer of 100% mineral spirits on top of product until it is completely covered and do not move pail until ready to reuse. When ready, stir thoroughly with a power mixer. Keep container tightly closed between applications to minimize surface skinning.

Is there a mildewcide in GacoRoof? Does GacoRoof mold or mildew?
There is no mildewcide in GacoRoof, because mildew does not grow on the surface of GacoRoof. Unlike acrylic coatings, GacoRoof is inert and does not provide a food source for mildew or mold.

Can my GacoRoof be pressure washed?
You can pressure wash GacoRoof at a low pressure (below 2,500 psi).

Does GacoRoof have a UL (Underwriters Laboratory) Approval Rating?
Yes, GacoRoof is UL rated when applied to a non-combustible surface.

Can GacoRoof be applied to roof decks or walkways?
Silicone can be slick, especially when the surface is wet, so GacoRoof should not be used for areas with foot traffic.

GacoDeck Kit is a better choice for roof decks.

I know that GacoRoof is perfect for flat roofs. Can I use GacoRoof on my peaked roof?
GacoRoof does cover peaked roofs as well as flat roofs. Use extreme caution when on a pitched roof. Follow all safety guidelines to avoid injury.

The reason that we emphasize our flat roof coverage is that flat roofs are notorious for having puddles and drainage problems and acrylics degrade rapidly under those conditions. Up until now, the only choice for building owners with flat roofs was smelly hot asphalt or recoating every 3 years with an acrylic.

Since both coats are white, how can I see where to apply the second coat?
Snap chalk lines as needed to see where to apply the second coat. Alternatively, GacoRoof Colorant can be used to tint one coat (base or top) gray, providing greater color contrast between the two coats.

GacoRoof_Flyer_Benefits_1 GacoRoof_Flyer_Benefits_2


GacoRoof Brochure | GacoRoof Benefits Flyer | GacoRoof Low VOC Benefits Flyer | Liquid Roof Tape Benefits Flyer


Source: GacoRoof Instructions

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