High-Density HDPE Self-Adhesive Waterproof Membrane – Welded

Product Overview

This high-density HDPE self-adhesive waterproof membrane is a pre-applied waterproofing system for basements, tunnels, foundations and underground structures. The membrane combines a strong HDPE sheet with a pressure-sensitive bonding layer and protective surface designed to bond permanently with freshly placed structural concrete.

The welded version uses hot-welded side and end laps to create continuous seams. After concrete placement, the adhesive layer forms an integral bond with the structure, helping prevent lateral water migration between the membrane and concrete if local damage occurs.

How the Pre-Applied System Works

The membrane is installed before reinforcement and concrete placement. Reinforcement can be positioned above the completed membrane without a conventional screed protection layer when the approved construction method is followed. Fresh concrete is then poured directly against the bonding surface, creating a reverse-bonded waterproofing assembly.

Because the membrane remains bonded to the structure, normal foundation settlement is less likely to create a water path between the waterproofing layer and the concrete. Correct seam welding, detailing and site protection remain essential for system performance.

Key Benefits

• High-strength HDPE sheet resists puncture and construction damage.

• Hot-welded laps create consistent, testable seam connections.

• Pre-applied bonding helps control lateral water migration.

• Permanent adhesion to newly placed structural concrete.

• No open flame, fuel or solvent is required during membrane installation.

• Available for complex underground layouts, vertical walls and horizontal slabs.

• High peel strength, tear resistance and low-temperature flexibility.

• Can reduce waterproofing build-up and simplify the construction sequence.

• Factory-direct supply for contractors, distributors and OEM projects.

Typical Applications

• Basement floor slabs and retaining walls.

• Underground foundations and civil building structures.

• Subways, metro stations and railway tunnels.

• Utility tunnels, shafts and underground passages.

• Reservoirs, canals and water-retaining infrastructure where specified.

• Landfills and wastewater treatment projects.

• Industrial and civil structures using pre-applied or reverse-bonded waterproofing.

Final selection must consider hydrostatic pressure, substrate, joint design, exposure, concrete placement method and local project requirements.

Available Construction

• Composite membrane thicknesses: 1.2 mm, 1.5 mm, 1.8 mm and 2.0 mm.

• Typical bare HDPE film thicknesses: 0.85 mm, 0.95 mm, 1.05 mm and 1.2 mm according to membrane grade.

• Reference adhesive thickness: 0.2-0.3 mm where applicable.

• Standard colors: white or project-specified light colors.

• Reference roll formats include 1.2 m × 20 m and 2.0 m × 20 m; confirm the current production specification before ordering.

Technical Performance

The following values are based on the existing product data for the 1.2-2.0 mm membrane range. Confirm the latest technical data sheet and approved project specification before purchase.

• Tensile strength of HDPE sheet: approximately 21-28 MPa depending on thickness; tested to ASTM D412.

• Elongation at break: typical value 500%; tested to ASTM D412.

• Puncture resistance: approximately 800-1,350 N depending on membrane grade; tested to ASTM E154.

• Peel adhesion to concrete: reference value 1,800 N/m +300 for the listed construction; tested to ASTM D903.

• Peel adhesion of welded joints: reference values 10,000-15,000 N depending on thickness; tested to ASTM D6392.

• Low-temperature flexibility: ≤-25°C without cracking; tested to ASTM D1970.

• Dimensional stability: reference requirement ≤1%; tested to ASTM D1204.

Installation Guide

1. Prepare the Base

The working surface must be stable, reasonably level and free from standing water, sharp projections and loose debris. Remove objects that could puncture the sheet. Complete approved corner, joint and penetration details before large-area installation.

2. Lay Out the Membrane

Plan membrane direction and seam locations before installation. Stagger short-end joints and avoid concentrating multiple overlaps at one point. Position the bonding surface toward the concrete to be placed and keep exposed lap areas clean and dry.

3. Weld the Seams

Hot-weld side and end laps with compatible wedge or hot-air equipment. A typical lap width is 100 mm, subject to the project method statement. Welding temperature and speed must be established by site trials because equipment, ambient conditions and membrane thickness affect the correct settings.

For double-seam systems, create two parallel welds with an air channel for testing where specified. Inspect the seam continuously and repair contamination, incomplete fusion or damage before proceeding.

4. Treat Corners and Penetrations

Use compatible prefabricated pieces or carefully cut and hot-air-welded membrane details at internal corners, external corners, pipes, piles and construction joints. These locations should be inspected before reinforcement limits access.

5. Inspect and Place Concrete

Check the complete high-density HDPE self-adhesive membrane for punctures, open seams, wrinkles and damaged details. Repair defects with compatible HDPE materials. Protect the system during reinforcement work, then place concrete against the prepared bonding surface according to the approved method.

Quality Control Checklist

• Verify membrane type, thickness, batch and roll condition before installation.

• Keep welding areas clean and free from dust, water and adhesive contamination.

• Complete trial welds and seam tests at the start of each shift or when conditions change.

• Inspect penetrations, terminations, corners and construction joints separately.

• Repair damage before reinforcement and concrete placement.

• Record inspections and tests required by the project quality plan.

Application Precautions

• Use trained installers and approved welding equipment.

• Do not use damaged rolls or install over sharp, unstable or contaminated surfaces.

• Protect the membrane from prolonged unnecessary exposure and construction traffic.

• Keep reinforcement supports and tools from puncturing the HDPE sheet.

• Follow the current technical data sheet, method statement and project safety requirements.

• Contact the technical team when the structure includes unusual joints, piles or complex penetrations.

Frequently Asked Questions

What is a high-density HDPE self-adhesive membrane?

It is a polymer sheet waterproofing system that combines an HDPE barrier with a bonding layer designed to adhere to newly placed concrete. The welded type connects adjacent sheets through heat-welded laps.

Where is the welded membrane normally used?

Typical uses include basement slabs, foundation walls, tunnels, metro structures and other below-grade projects where continuous welded seams and pre-applied bonding are specified.

What is the difference between welded and adhesive-lap HDPE membrane?

The welded version joins HDPE laps with heat-welding equipment, while an adhesive-lap version uses a prepared adhesive overlap. Selection depends on project detailing, installation skills, testing requirements and site conditions.

Can concrete be poured directly against the membrane?

Yes, this product is designed as a pre-applied system. Concrete is placed against the bonding surface after the membrane, seams and details have passed inspection.

Project Supply and Technical Support

Hongyuan supplies HDPE waterproof membrane for contractors, distributors and infrastructure projects. Send the drawing, application area, membrane thickness, roll size, seam type, quantity and applicable standard for a project-specific quotation.

Installation guide: https://waterproofingbest.com/news/hdpe-self-adhesive-membrane-installation-guide.html