Composeal Grey 40 Mil PVC Waterproofing Membrane Installation Instructions
Composeal Grey 40 Mil PVC is a professional-grade waterproofing membrane designed for use beneath tile and stone installations where long-term moisture protection is required. Manufactured from durable flexible PVC, the membrane creates a waterproof barrier that helps protect underlying structures from water intrusion and costly secondary water damage.
Common applications include custom shower pans, wet rooms, Roman tubs, whirlpool bath enclosures, fountains, roof decks, and other waterproofing projects that require a dependable moisture barrier beneath mortar bed installations.
Proper installation is essential for long-term performance. Before beginning installation, verify that the substrate, drain assembly, and surrounding framing comply with applicable building codes and manufacturer recommendations. Carefully follow the installation procedures outlined below and perform a flood test before covering the membrane with mortar or finished tile surfaces.
These instructions are based on the current manufacturer installation guidelines for Composeal Grey 40 Mil PVC waterproofing membrane.
Step 1: Prepare the Subfloor
Before installing Composeal Grey 40 Mil PVC, ensure the subfloor is properly sloped toward the drain at a rate of 1/4 inch per foot. If necessary, use cement mortar to create the required slope. The subfloor must be clean and free of loose debris, gravel, nail heads, or any protrusions that could damage the membrane during installation.
A properly prepared substrate helps ensure effective drainage and long-term waterproofing performance.
Step 2: Extend the Membrane Up the Walls
Install the membrane so it extends up the surrounding walls a minimum of 3 inches above the finished curb height. Allow sufficient material to cover the outside face of the curb and extend a few inches beyond the shower area where required.
For curbless shower installations, the membrane should be fastened at least 6 inches above the finished floor height to maintain proper waterproofing protection.
Carefully position the membrane before fastening to avoid wrinkles, folds, or unnecessary stretching.
Step 3: Prepare Wall Studs
Wood studs should be notched approximately 1/2 inch to the height of the shower pan liner. This allows the membrane thickness to sit flush with the face of the framing and helps prevent wall board bulging during installation.
For metal stud construction, install furring strips between 1/4 inch and 1/2 inch thick above the top of the membrane. This creates a flat and plumb wall surface for backer board installation while accommodating the thickness of the waterproofing membrane.
Proper framing preparation helps ensure a professional finished tile installation and prevents uneven wall surfaces.
Step 4: Fasten the Membrane
Once the membrane is properly positioned, fasten it a minimum of 3 inches above the finished curb height. For wood framing, use flat-head roofing nails or staples. For metal stud construction, use drywall screws with washers.
To maintain the waterproof integrity of the installation, do not place fasteners anywhere below the 3-inch height above the curb. Penetrating the membrane below this level may create a potential leak path and compromise the waterproofing system.
Verify that the membrane remains smooth and properly aligned before completing all fastening points.
Step 5: Fold Corners Without Cutting
At outside corners and curb transitions, carefully fold the membrane rather than cutting it. Corner folds should be positioned between studs or accommodated using notched framing or furring strips to maintain a flat and plumb wall surface.
Do not cut the membrane at corners. Maintaining continuous waterproof coverage is critical to the long-term performance of the shower pan and waterproofing assembly.
Preformed Composeal PVC corners and curb protectors may be used to reinforce critical waterproofing areas and simplify installation.
Step 6: Install the Drain Assembly
Use a bolt-down clamping-ring drain equipped with weep holes. The sub-drain lip should be installed flush with the subfloor to ensure proper integration with the waterproofing membrane.
Trim the membrane opening only to the size of the drain opening itself. Do not cut the membrane out to the bolt holes. Pierce the membrane at bolt locations using a nail or similar tool to create a tight fit around the bolts.
To create a watertight seal between the membrane and the sub-drain assembly, apply Compotite Elastiseal Pro or a 100% mold and mildew resistant silicone sealant as recommended by the manufacturer.
Once the membrane is secured, firmly tighten the clamping ring and verify proper drain assembly installation before proceeding with flood testing.
Step 7: Perform a 24-Hour Flood Test
Before installing mortar, tile, or other finish materials, perform a flood test to verify the waterproof integrity of the installation. Plug the sub-drain and fill the shower pan with water. Allow the water to remain in place for a minimum of 24 hours.
Inspect the shower pan, drain connection, and surrounding areas for signs of leakage. This test helps confirm that the membrane, drain assembly, and seam details have been properly installed before the waterproofing system is covered.
After confirming a watertight installation, place a small amount of pea gravel or other porous material around the drain weep holes to help prevent blockage when the mortar bed is installed.
Composeal Installation Components
Several accessory products are available to simplify installation and help ensure long-term waterproofing performance. These products are specifically designed for use with Composeal Grey 40 Mil PVC waterproofing membrane.
Weld-Tite Flexible Vinyl Cement
Weld-Tite Flexible Vinyl Cement is used to solvent weld overlapping PVC membrane sheets together, creating a waterproof bond with instant contact strength. Use only Compotite-approved PVC cement when joining Composeal membrane sections.
Compotite Elastiseal Pro
Elastiseal Pro is used to bond Composeal Grey PVC membrane to the sub-drain assembly and create a watertight connection at the drain. Elastiseal Pro is not intended for welding PVC membrane seams together.
PVC Corners and Curb Protectors
Preformed Composeal PVC corners and curb protectors are designed to reinforce waterproofing at corners, curbs, and other critical transition areas. These accessories are installed using Weld-Tite Flexible Vinyl Cement and help simplify installation while improving waterproofing protection.
Seam Welding Instructions
When larger waterproofing areas require multiple membrane sections, Composeal Grey sheets can be welded together to create a waterproof bond using Compotite Weld-Tite Flexible Vinyl Cement. Proper seam welding is essential to maintain the waterproof integrity of the installation.
Position membrane sheets with a minimum 2-inch overlap, ensuring the upper lap edge faces the direction of water flow. Fold back the top sheet and apply Weld-Tite Flexible Vinyl Cement to both surfaces being joined.
Allow the adhesive to become slightly tacky before bringing the surfaces together. Firmly press or roll the overlap area to create a tight bond. Always inspect welded seams to verify complete adhesion before proceeding with installation.
Specifications & Code Compliance
Composeal Grey 40 Mil PVC complies with ICC-ES standards for the United States and Canada (Report PMG-1459) and NES (PCR SP 102).
The membrane has received municipal approvals where required, including the City of Los Angeles (RR#4398), City of Philadelphia, Metropolitan Dade County, Florida, and the Commonwealth of Massachusetts. Approval is no longer required in New York City for concealed PVC waterproof membranes.
Composeal Grey 40 Mil PVC also complies with Corps of Engineers specifications for PVC shower pan materials and meets the requirements of FHA Publication 4900.1.
The membrane meets and exceeds the engineering requirements established by ASTM. ASTM D4551 is the recognized testing standard for PVC shower pan membranes.
Limitations
Composeal Grey should not be used as a liner for pools containing fish or water plants.
Technical Support
The Tile Council of North America (TCNA) Handbook for Ceramic, Glass and Stone Tile Installation provides general guidelines for installations requiring waterproof membranes. Additional technical support, installation materials, and product literature are available directly from Compotite.
For additional product information and technical resources, contact Compotite Corporation at 1-800-221-1056 or visit the manufacturer's website.
Helpful Resources
- Composeal Grey 40 Mil PVC Waterproofing Membrane SDS
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- Composeal Waterproofing Videos
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