Installation Guide Specification for Recoating Silicone Roofs

Recoating Existing Silicone Coated Roofs

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1.01    SUMMARY 

  • Provide labor, materials, equipment and supervision necessary to install spray applied silicone coating system as outlined in this specification to recoat seamless weatherproofing over existing silicone coating roofing.
  • The manufacturer's application instructions for each product used are to be considered part of these specifications and should be followed at all times.


  • Submit product data sheets and literature verifying fire ratings and physical properties of materials.
  • Submit material safety data sheets.


  • Supplier Qualifications: The SRC Silicone Roofing System for existing silicone coated roofs, as supplied by National Coatings Corporation, is approved for use on the project.

  • Applicator Qualifications: The applicator shall be approved by National Coatings Corporation to apply the system. Manufacturer's written verification of applicator approval is required.


  • Containers and Packaging: Deliver materials in original sealed containers, clearly marked with: manufacturer’s logo; full product name; and lot number(s).
  • Storage: Store materials between 40ºF and 100ºF with careful handling to prevent damage to products. If conditions exceed these ranges, special consideration in storage must be taken. Do not store at high temperatures in direct sunlight.
  • Store and dispose of solvent-based materials, and materials used with solvent-based materials, in accordance with requirements of local authorities having jurisdiction.
  • Protection: Protect all materials from freezing and other damage during transit, handling, storage, and installation.


  • These recommendations are for maintenance of an existing coating system and not intended for correction of badly deteriorated roofing systems that may need replacement.
  • These minimum recommendations for material usage are for ideal conditions. The number of gallons per 100 square feet may need to increase due to uneven application, rough surface texture, wind conditions while spraying and/or other variables.

  • Wet insulation must be thoroughly evaluated and then addressed with removal or other measures. Consult a National Coatings Technical Consultant regarding the need for moisture surveys and other assessments.

  • Structural cracks should be referred to the appropriate National Coatings Technical Consultant.

  • This installation guide specification assumes that the deck, if plywood, has no dry rot, and is in sound condition, or has been repaired.

  • Do not apply materials unless surface to receive silicone roofing system is clean, dry and prepared as specified.

  • Install all material in strict accordance with all published safety, weather, or applicable regulations of the manufacturer and/or local, state, and/or federal agencies which have jurisdiction.

  • The entire system shall be fully adhered to the surface on which it is applied. Voids left under the system by creating bridges are not acceptable.

  • Do not proceed with application of coating or sealing materials when temperature is less than 35oF. No coating system shall be applied if weather will not permit it to dry prior to exposure to precipitation or freezing.

  • Heavy puddles of coating on the roof are not acceptable.

  • Instructions for use of all roofing materials and application equipment should be read and followed at all times.

  • As a general principle, to prevent the ponding of water, install additional drains as necessary or install drainage systems with sprayed polyurethane foam (SPF).
  • This specification does not extensively outline procedures for preparation and finishing of drains, vents, ducts, flashings, parapet walls, sheet metal work, etc. This work should be outlined by the contractor before work commences, and shall be performed observing good trade practices.



  1. The roofing system is the SRC Silicone Roofing System Provided by National Coatings Corporation.

  2. Physical Properties of Cured Roofing System:

    1. The roofing system shall have good resistance to ponding water.

    2. The roofing system shall contain no plasticizers.

    3. The roofing system shall contain no migrating fire retardants.

    4. The roofing system shall have a Class A fire rating on a noncombustible deck when tested according to the procedures outlined in ASTM E-108.

    5. The roofing system shall also meet the following physical property requirements:


ASTM Method


Tensile Strength, psi (Max @ 73ºF)


Minimum 247

% Elongation @ Break (73ºF)


Minimum 237

Weathering/UV Resistance


No Degradation - 5000 hours

Permeance, perms



Volume Solids %
Weight Solids %




  • Flashing, adhesives, thinners, elastomeric caulking compounds, primers, and similar materials shall be approved by the manufacturer of the coatings. All materials used shall be applied in accordance with its manufacturer's recommendations.


  • For recommended spray equipment guidelines, please refer to National Coatings Technical Paper "TP-117 Silicone Coatings Spray Guide", or consult the spray equipment manufacturer directly.



  • Compliance: Comply with manufacturer’s product data, including product technical bulletins and product guide specification instructions.


  • Inspect surfaces which will receive the SRC Silicone Roofing System to make sure they are clean, smooth, sound, properly prepared, and free of moisture, dirt, debris, or other contamination.

  • Verify that all roof penetrations, mechanical equipment, cants, edge metal, and other on-roof items are in place and secure.

  • Verify that all critical areas around the immediate vicinity of the spray area are suitably protected.

  • Verify all roof drains are clean and in working order.

  • Verify that all air conditioning and air intake vents are suitably protected or closed.

  • When properly applied, SRC silicones from National Coatings are not affected by ponding water. However, the National Roofing Contractors Association (NRCA) considers ponding water objectionable due to structural and health concerns. The NRCA recommends that all roof assemblies have positive drainage. NCC strongly recommends following established NRCA guidelines.


  • All surfaces to be coated must be clean, sound, dry and free of any dirt, grease, oil, debris or other contaminants which would interfere with proper adhesion. Pay particular attention to the low areas on the roof, where more contaminants may have settled. Loose coating should be removed prior to application of coating. Any wet areas must be removed and/or dried out prior to application of coating.

  • Adhesion testing should be completed as per NCC technical bulletin.

  • If recoating SPF, exposed SPF areas must be brushed with a stiff bristle broom to remove the

    degraded SPF prior to caulking with Flashing Grade Silicone Sealant and coating.

  • Caulk or fill all cracks, holes or other surface imperfections with Flashing Grade Silicone Sealant. All caulk or sealant must be thoroughly dry before application of coating. NOTE: Silicone sealants are not compatible with acrylic coatings.

  • If recoating SPF roof - Start repair of large damaged and deteriorated areas by removing existing coating and SPF down to dry, good quality SPF. This requires close observation to insure that the removal operation is extended both horizontally and vertically to the point where all wet, contaminated, and deteriorated SPF has been removed. The damaged SPF must be removed by mechanical scarifying equipment to a minim mum depth of 1⁄2 “or until good SPF is determined, whichever is greater. Removal of SPF by hand is not acceptable. These areas shall receive an extra two coats of SRC roof coating before coating the entire roof. Large or deep areas of foam removal may require the application of additional foam prior to coating. Apply a minimum of 1⁄2” new SPF. Do not remove an area larger than can be refoamed and base coated in the same day.

  • Seal all HVAC duct work joints as needed with Flashing Grade Silicone Sealant and reinforcing polyester fabric. Coat entire duct assembly with a 1 gallon coat of SRC roof coating.

  • Reseal around all mechanical equipment and roof penetrations with Flashing Grade Silicone Sealant architectural sealant and, where possible, T272 reinforcing fabric

  • At parapets, firewalls, expansion joint curbs, mechanical curbs or skylights Flashing Grade Silicone Sealant and T272 in a three course detail to overlay all uncured flashing located less than 5 inches above the deck. Flashing extending above 5 inches shall be flashed in using Flashing Grade Silicone Sealant only.


  • After thorough preparation as necessary, the entire roof shall receive the SRC Silicone Roofing System consisting of silicone coating in one or two passes over entire roof surface to achieve a final thickness of:

    • 22 mils (1.5 gallons per square) minimum for a 10 year warranty
    • 30 mils (2.0 gallons per square) minimum for a 15 year warranty
    • 38 mils (2.5 gallons per square) minimum for a 20 year warranty
  • While spraying the silicone coating, special effort should be made to have pass lines overlap on membrane seams as to provide additional coating thickness on the seams.

  • All coating edges shall be cut evenly in a uniform manner so as to provide an aesthetically pleasing appearance.


  • In case of manufacturer’s labor and material warranty - Manufacturer’s Field Services: Inspection by National Coatings Corporation’s representative shall be made to verify the proper installation of the system. Any areas that do not meet the minimum standards for application as specified herein shall be corrected at the contractor's expense. Manufacturer's inspection or verification shall not constitute acceptance of responsibility for any improper application of material.

3.06    CLEANING

Surfaces not intended to receive the SRC Silicone Roofing System shall be protected during the application of the system. Should this protection not be effective, or not be provided, the respective surfaces shall be restored to their proper conditions by cleaning, repairing or replacing. All debris from completion of work shall be completely removed from the project site. Mineral Spirits can be used to remove coating from unintended surfaces.


The following materials listed in these recommendations are available from National Coatings Corporation:

    1. SRC 740 or SRC 750 High Solids Silicone Roof Coating

    2. Flashing Grade Silicone Sealant

    3. T272 polyester-reinforcing fabric 6-inch, 10-inch, 20-inch and 40-inch

    4. INDUSTRIAL CLEANER water-based, biodegradable cleaner