Millennium Water Block Mastic (BP-300)

1 of 55 products in this brand
Millennium Water Block Mastic (BP-300) is a gray colored, high performance, low VOC, non-curing, permanently flexible gun grade mastic. It maintains a positive seal by remaining flexible and adhered to all approved substrates. It is a non-curing, non-skinning secondary sealant designed for unexposed waterproofing applications.

Product Type: 1K (1 component) Sealant, Solventborne Sealant

Application Area: Roofing Substrates

Compatible Substrates & Surfaces: Glass, Gypsum, Masonry, Metal, Plastics, Wood

Application Method: Gun

Features: Excellent Substrate Adhesion, Excellent Water Resistance, Flexible, High Performance, Low Temperature Flexibility, Low VOC, Primerless

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Identification & Functionality

Product Image

Base Polymer

Synthetic Rubber

Features & Benefits

Key Attributes
Features Benefits
Low VOC formula (<150 g/L) Suitable for use in VOC regulated markets
Excellent adhesion to clean and dry substrates. No primer required Adheres to concrete, masonry, gypsum, metal, glass, plastic and wood surfaces
Excellent gunnability at low temperatures Wide application temperature range
Water resistant, even under immersion conditions Long term moisture barrier
Non-skinning and noncuring Permanently flexible even at low temperatures

Applications & Uses

Application Area
Application Method
Compatible Substrates & Surfaces
Basic Use

Millennium Water Block Mastic is a non-curing, non-skinning secondary sealant designed for unexposed waterproofing applications. Millennium Water Block Mastic can be used:

  • Behind termination bar
  • Under roof drains
  • Acoustical sealant
  • Roof panel rib sealant
  • Vapor barrier sealant
Application Instructions

Surface Preparation: All work surfaces should be clean, dry, free of dirt, dust, debris, oils, un-adhered coatings, deteriorated membrane and other contaminants that may result in a surface that is not sound or is uneven. If necessary, clean the surface to receive the Millennium Water Block Mastic with an approved surface cleaner.

  1. Cut nozzle on cartridge to allow proper bead Installation.
  2. Apply an approximately 1/2” (1.3cm) size bead (or appropriate size bead to completely seal void) of Millennium Water Block Mastic between the objects to be sealed.
  3. Installll product and fasten accordingly. Note: Millennium Water Block Mastic is not intended to be used as a structural sealant or to replace mechanical fastening. It is intended for waterproofing only.
  4. For drain applications, install a continuous bead of Millennium Water Block Mastic in between roof membrane and drain bowl. Install drain clamping ring according to drain manufacturers recommendations.
  5. Note: This is a non-skinning, non-curing sealant and is intended for unexposed applications only.
  • Talc, dust, oil, ice, snow, or wet conditions inhibit good adhesion.
  • Clean and dry surfaces are necessary for proper Installation of this product.
  • Not recommended for direct contact with insulating glass sealants.
  • Not to be used in locations exposed to direct UV light.
  • Not to be painted.
  • Use only in unexposed areas.


Typical Physical Properties
ValueUnitsTest Method / Conditions
AdhesionExcellent to most clean, dry surfaces-ASTM C794
Water ResistanceNo adhesion loss, no shrinkage, no chalking--
Flash Point40.0°CASTM D 56
VOC Contentmax. 150g/LASTM D 3960
Solids Contentmin. 85%ASTM C681
Weight per Gallon10.5lbsASTM D 1475
Typical Properties
ValueUnitsTest Method / Conditions
Service Temperature-40 - 93°CASTM D 3359
Application Temperature-6 - 49°CASTM C603

Packaging & Availability

Packaging Type
Packaging and Coverage

Millennium Water Block Mastic is available in the following package:

Cartridge Size Part # Cartridges/Case
10.3 fl. oz. (305 mL) CT-0304-GR 30

Coverage rate will be approximately 10-12 lineal feet (3.0 - 3.7m) for a 1/2” (1.3cm) bead.

Storage & Handling

Shelf Life
24 Months
Storage Information

Store material in original unopened packaging at temperatures between 40°F-110°F (4°C-43°C).