TL-0001 — Chemical Compatibility with Other Building Materials and Sealants Technical Letter

Frequently during the design of an assembly, the designer will question the chemical compatibility of self-adhered flexible flashings with other materials. Vycor® Self-Adhered Flashings (Vycor Plus, Vycor V40, Vycor Aluminum, Vycor PRO, and Vycor Deck Protector®) are chemically compatible with most substances and products that are normally present in common application environments. Vycor Self-Adhered Flashings are compatible with acids, bases and salts. Generally, there is no chemical compatibility issue if a material contacts the film surface of the self-adhered flashing. If the contact area is the adhesive component of the flashing, there is need to investigate further. As a general rule, the material must be sound, functional and firmly bonded to the substrate. The design of the connection between the two materials will vary depending on the composition of the material. Some of the more common materials are detailed below.

Building Materials

Vycor® Self-Adhered Flashings are applied directly to exterior sheathing panels such as plywood (including fire-treated plywood), oriented strand board (OSB), exterior gypsum board, glass mat surfaced gypsum board, and extruded polystyrene. Vycor flashings are compatible with chromated copper arsenate (CCA), alkaline copper quaternary (ACQ), ammoniacal copper zinc arsenate (ACZA), pressure-treated woods and pressure-treated plywoods.

Windows & Doors

The rubberized asphalt of Vycor Plus, Vycor V40, Vycor Aluminum, and Vycor Deck Protector is compatible with rigid polyvinyl chloride (PVC), but not plasticized polyvinyl chloride. Vycor PRO is compatible with rigid and plasticized PVC nailing flanges. Some arched/round shape windows may use a plasticized PVC nailing flange. Consult with the window manufacturer to determine if the nailing flange is constructed of plasticized PVC. For further details refer to Technical Letter 6, Chemical Compatibility with Vinyl Windows. Note: Per ASTM E2112, “The application of sealant to the exterior face of the (window) flange is not necessary if using self-adhesive type flashing over the mounting flange.”

Weather Resistive Barriers

Vycor® Self-Adhered Flashings are applied to the structural substrate. They should be integrated with the weather resistive barrier to form water-shedding laps.

Vycor Self-Adhered Flashings are compatible with the following weather resistive barriers:

  • Vycor enV®-S™
  • Vycor enV® (cured liquid)
  • Spun-Bonded Polypropylene
  • Spun-Bonded Polyethylene
  • Red Rosin Paper
  • Asphalt Saturated Felt
  • Spun-Bonded Polyethylene
  • Red Rosin Paper
  • Asphalt Saturated Felt
  • Polyurethane Coatings
  • Polyethylene Sheet/Visqueen
  • Asphaltic Dampproofing
  • Perm-A-Barrier® Systems
  • OSB Panels with integrated WRB coatings (such as Huber Zip System® panels)

Sealant and Caulking Materials

Most sealants are chemically compatible with Vycor® Self-Adhered Flashings provided that the sealant is applied to the high- density polyethylene film component of the flashings. There are various sealant formulations on the market that may or may not be compatible with the adhesive layer of Vycor Self-Adhered Flashings. For further details, refer to Technical Letter 7, Chemical Compatibility Between Vycor Self-Adhered Flashings and Sealants.

Non-Compatible Materials

Vycor® Self-Adhered Flashings are not compatible with the following substances:

  • Creosote
  • Pentachlorophenol
  • Polysulfides
  • Diesel Fuel
  • Gasoline/Oil
  • Hydrocarbon Solvents
  • EPDM*
  • Plasticized PVC*
  • TPO*
  • Uncured Neoprene
  • High concentrations of pitch (resin from soft wood)

* Vycor PRO is compatible with plasticized PVC window flanges, EPDM and TPO. Vycor PRO is intended for non-roof applications only.


Only GCP approved primers should be used with Vycor® Self-Adhered Flashings. Vycor Plus, Vycor V40, Vycor Aluminum, Vycor PRO and Vycor Deck Protector are compatible with the following GCP primers:

  • Perm-A-Barrier® WB Primer
  • Bituthene® Primer B2 LVC
  • Perm-A-Barrier® Primer Plus | North America Customer Service: 1 877-4AD-MIX1 (1 877-423-6491)

GCP Applied Technologies Inc., 2325 Lakeview Parkway, Suite 450, Alpharetta, GA 30009, USA
GCP Canada, Inc., 294 Clements Road, West, Ajax, Ontario, Canada L1S 3C6
This document is only current as of the last updated date stated below and is valid only for use in the United States. It is important that you always refer to the currently available information at the URL below to provide the most current product information at the time of use. Additional literature such as Contractor Manuals, Technical Bulletins, Detail Drawings and detailing recommendations and other relevant documents are also available on Information found on other websites must not be relied upon, as they may not be up-to-date or applicable to the conditions in your location and we do not accept any responsibility for their content. If there are any conflicts or if you need more information, please contact GCP Customer Service.

Last Updated: 2022-08-02