R Guard Joint & Seam Filler

R-Guard Joint & Seam Filler — Gun-Grade STP Crack & Joint Filler for Air Barrier and Waterproofing Systems

PROSOCO R-Guard Joint & Seam Filler is a single-component, fiber-reinforced, silyl-terminated polymer (STP) gun-grade crack and joint filler, adhesive, and detailing compound designed for use in air barrier, waterproofing, and flashing membrane systems. It is engineered for contractors who need a reliable, flexible material to fill openings and create transitions where continuous support of fluid-applied membranes is required. Part of the R-Guard product line, it is suited to all climates and a wide range of substrates. It may also be used to repair cracks or fill voids after the primary R-Guard air barrier has been applied.

Unlike conventional sealants that force a choice between silicone or polyurethane chemistry, Joint & Seam Filler combines the best properties of both in a single-component formula that is easy to gun, spread, and tool. Its fiber reinforcement bridges larger gaps and provides continuous support without requiring reinforcing tapes at sheathing joints, inside corners, or outside corners — dramatically reducing surface preparation time on the jobsite.

Key Features & Benefits

Silyl-Terminated Polymer (STP) Chemistry

Joint & Seam Filler combines the flexibility and weathering performance of silicone with the adhesion and toolability of polyurethane in a single product. This hybrid STP chemistry means contractors do not have to stock or switch between two different sealant types for air barrier and waterproofing detailing work.

Fiber-Reinforced Formula Bridges Larger Gaps

The fiber reinforcement allows Joint & Seam Filler to bridge larger gaps and provide continuous support for fluid-applied flashing membranes, waterproofing, and air barrier components. This is particularly valuable at sheathing joints, inside corners, and outside corners where conventional sealants or tapes may fail to provide adequate reinforcement.

Eliminates Reinforcing Tapes at Joints and Corners

By eliminating the need for reinforcing tapes at sheathing joints, inside corners, and outside corners, Joint & Seam Filler dramatically reduces surface preparation time. Fewer materials and fewer steps translate directly to faster installation and lower labor cost per project.

Bonds to Damp or Dry Surfaces in All Climates

Joint & Seam Filler bonds directly to damp or dry surfaces and cures under a variety of weather conditions, making it suitable for all climates. Contractors are not forced to delay application or wait for surfaces to fully dry before proceeding.

Gun-Grade — Easy to Apply, Spread, and Tool

The gun-grade formulation dispenses cleanly through a standard caulk gun and can also be spread and tooled, giving applicators flexibility in how they work the material into joints, corners, and transitions. This versatility supports both precise detailing and bulk filling applications.

Low VOC Content — Green Building Compliant

Joint & Seam Filler contains less than 30 g/L VOC content, well below the SCAQMD 1168 architectural sealant limit of 250 g/L, and is compliant with the California Air Resources Board (CARB) 2007 requirements. It is also CDPH Standard Method v1.2-2017 compliant with total VOCs of 0.5 mg/m³ or less after 14 days, supporting LEED v4.x, LEED 2009, CALGreen, Living Building Challenge 3.x, WELL v2, and Fitwel submittals. The product carries an SCS Indoor Advantage Gold certification for select applications and holds a Declare label (PRO-0002) with Red List Free status under Living Building Challenge 3.0.

Common Applications

Sheathing Joint Filling

Apply at sheathing panel joints to fill gaps, provide flexible reinforcement, and create a continuous substrate for fluid-applied air barrier or waterproofing membranes — without the need for additional reinforcing tape.

Inside and Outside Corner Detailing

Tool Joint & Seam Filler into inside and outside corners to create smooth, supported transitions that fluid-applied membranes can bridge without bridging failures or delamination.

Crack Repair After Air Barrier Application

Use to repair cracks or fill voids that appear after the primary R-Guard air barrier membrane has been applied, restoring continuity of the system without requiring full re-application.

Transitions Requiring Flexible Gap Bridging

Fill openings and create transitions where flexible reinforcement is required to bridge larger gaps and provide continuous support beneath fluid-applied flashing membranes, waterproofing, or air barrier components.

Part of a Building-Wide Air Barrier System

Integrate Joint & Seam Filler into a continuous, building-wide air barrier system, or use it to prepare surfaces for conventional waterproofing or air barrier components.

Compatible Materials

• Damp surfaces
• Dry surfaces
• Gypsum sheathing
• Substrates requiring R-Guard fluid-applied air barrier membranes
• Substrates requiring fluid-applied waterproofing membranes
• Substrates requiring fluid-applied flashing membranes

Product Documents

• Product Data Sheet
• Product Data Sheet (Canadian French)
• Product Data Sheet (Spanish)
• Safety Data Sheet
• Safety Data Sheet (Spanish)
• Safety Data Sheet (Canadian French)
• VOC Compliance
• Product Test Data (ASTM E2357)
• Product Test Data
• LEED Verification Letter
• SCS Certification
• LBC Red List Conformant Product Summary

Technical Specifications

Frequently Asked Questions

Q: Can Joint & Seam Filler be used on wet or damp surfaces?
A: Yes. Joint & Seam Filler bonds directly to both damp and dry surfaces and cures under a variety of weather conditions, so application does not need to wait for surfaces to fully dry.

Q: Does this product replace reinforcing tape at sheathing joints and corners?
A: Yes. The fiber-reinforced formula eliminates the need for reinforcing tapes at sheathing joints, inside corners, and outside corners, which dramatically reduces surface preparation time.

Q: Is Joint & Seam Filler compliant with LEED and other green building rating systems?
A: Yes. The product supports submittals for LEED 2009, LEED v4.x, CALGreen, Living Building Challenge 3.x, WELL v2, and Fitwel. It is CDPH Standard Method v1.2-2017 compliant, CARB 2007 compliant, SCS Indoor Advantage Gold certified (select applications), and carries a Declare label (PRO-0002) with Red List Free status under LBC 3.0.

Q: Can this product be used after the primary R-Guard air barrier has already been applied?
A: Yes. Joint & Seam Filler may be used to repair cracks or fill voids that appear after the primary R-Guard air barrier application has been completed.

Q: Is Joint & Seam Filler limited to R-Guard system applications?
A: No. While it is part of the R-Guard system, it can also be used to prepare surfaces for conventional waterproofing or air barrier components, and as part of a continuous building-wide air barrier system.