Waterproofing in Restoration and New Construction: A Critical Component

Co-authored by Jonathan Johansmeyer of W. R. MEADOWS.

Waterproofing plays a vital role in both restoration and new construction, serving a wide range of applications including planters, split slab assemblies, and below-grade structures. Moisture intrusion remains the leading cause of construction-related litigation, making waterproofing one of the most critical components in protecting the structural integrity of a building.

Understanding Waterproofing Membranes

Before diving into the technical aspects, it’s important to understand what a waterproofing membrane is designed to do. Whether fluid-applied or sheet-based, these membranes serve one primary function: to resist hydrostatic head pressure and prevent water ingress.

Hydrostatic head pressure refers to the pressure exerted by standing water against a structure. When a structure is built below grade and within the water table, it will inevitably be subjected to this pressure, which is measured in PSI. The waterproofing system must be able to withstand this force to prevent water infiltration.

Key Considerations When Selling Waterproofing Systems

There are many standards that govern the performance of waterproofing materials, including tests for adhesion, elongation, and tensile strength. However, for the purpose of understanding their classification, two primary standards should be your focus:

1. Cold Fluid-Applied Waterproofing:
   ASTM C836 – “Standard Specification for High Solids Content, Cold Liquid-Applied Elastomeric Waterproofing Membrane for Use with Separate Wearing Course.”
2. Sheet Waterproofing:
   ASTM D5385 – “Standard Test Method for Hydrostatic Pressure Resistance of Waterproofing Membranes.”
   A passing result for a sheet membrane indicates it can withstand hydrostatic pressure equivalent to 231 feet of water head.

Most cold fluid-applied membranes today are tested to ASTM C836. However, their hydrostatic head resistance is often not listed on the data sheet. Does that mean they aren’t waterproof? Short answer: no. If the material meets all ASTM C836 requirements, it is considered waterproofing. That said, always review the limitations section of the technical data sheet to ensure the product is approved for use in submerged conditions.

W. R. MEADOWS VERTIBARRIER NS has successfully passed ASTM D5385 testing.

Application and Coverage: Understanding Solids Content

Cold fluid-applied membranes are available in varying dry film thicknesses (DFT): 60, 90, or 120 mils. These can be installed with or without reinforcement fabric, depending on job-specific requirements. It’s important to use DFT (Dry Film Thickness) when estimating coverage, especially since materials vary in solids content.

Here’s the basic formula for estimating coverage:

(% Solids by Volume × 1604) ÷ Desired DFT (mils) = Coverage Rate (sf/gal)

Examples:

• At 100% solids and 120 mils:
  100% × 1604 ÷ 120 = 13.37 sf/gal
• At 85% solids and 120 mils:
  85% × 1604 ÷ 120 = 11.36 sf/gal

Understanding this formula is critical when helping contractors estimate materials accurately.

Reinforcement Fabric: Use It Wisely

Reinforcement fabric is often required at expansion joints or cracks greater than 1/16″, even when using a non-reinforced system. However, adding fabric will reduce the elongation properties of the membrane. To get a quick sense of this at the counter, try pulling apart a strip of reinforcement fabric — it’s tough for a reason.

This isn’t a warning against using reinforcement, but rather a reminder to consider how the material is expected to perform under specific conditions. Always follow manufacturer guidelines when detailing and specifying reinforcement.

If you’re selling or specifying waterproofing materials, a thorough understanding of how these systems are tested, applied, and perform under pressure is crucial to ensuring long-term success on the jobsite, and protecting the structures we build.

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