Waterproofing Solutions for Below-Grade Wall Surfaces – A Comprehensive Guide

In the realm of construction and home maintenance, ensuring the longevity and structural integrity of a building’s foundation is paramount. One crucial aspect often overlooked is the exterior surface damp-proofing of below-grade walls. These walls, often hidden beneath the ground, play a vital role in safeguarding your property against moisture infiltration and the potential damages it can inflict. In this comprehensive guide, we will delve into the importance of damp-proofing, its technical aspects, and the compliance measures necessary to secure your building’s foundation.

Foundation Wall Water Barrier

• Porous concrete foundations should be treated to avoid water seepage into the home.
• Builders treat below-grade walls with a damp-proof coating such as an asphalt emulsion.
• For more rigorous protection, a plastic drainage plane may be used in addition to the damp-proof coating.
• A layer of insulation, like rigid fiberglass or rigid polyurethane foam rated for soil contact, may be added.
• A gravel layer is included to provide proper backfill for drainage, allowing water to flow toward the foundation footing where a perforated drain pipe carries it away from the structure.

Scope

• Damp-proof the exterior surface of below-grade walls of basements and unvented crawlspaces.
• Ensure proper surface, vertical, and horizontal drainage are in place at the foundation.

Concrete

• Cover the exterior surface of poured concrete, concrete masonry, and insulated concrete forms with a damp-proof coating.
• Customize the concrete mixture to make it more impermeable to water migration.
• For concrete masonry block walls, coat the exterior surface with a layer of parging before applying the damp-proof coating.

Wood

• Use preservative-treated lumber and sheathing when installing wood products below-grade.
• Cover the entire exterior surface area with at least a 6-mil polyethylene sheeting attached to the wall with the appropriate adhesive.

Description

• Prevent foundation water issues by covering the exterior surface of the foundation walls with a damp-proof coating like asphalt emulsion.
• Ensure proper grading, deep roof overhangs, foundation drainage, gutters, and downspouts to manage water effectively.
• Implement vertical and horizontal drainage measures, including free-draining soil, geotextile drainage mat, and exterior footing drain pipes.
• Install a capillary break between the footing and foundation wall to prevent “rising damp.”
• Properly prepare masonry block walls with a layer of parging before applying the damp-proof coating.
• Customize concrete mixtures for more water impermeability.
• Use additives like admixtures to enhance water resistance based on climate and local codes.
• Consider using higher PSI concrete mix for foundation or below-grade walls.
• Follow local and national codes for preservative-treated lumber and moisture barrier for wood foundation walls.

Ensuring Success

• Damp-proofing below-grade walls is part of a comprehensive water management strategy that includes site grading, footing drainage, gutters, and water-resistant construction techniques.
• Follow the manufacturer’s instructions for the installation of damp-proofing products.

Cold Climates

• In all climates, but especially in cold climates where there are concerns with frost heave and adfreeze, ensure the ground surface slopes away from the foundation.
• Ensure good vertical drainage along the foundation wall by backfilling with free-draining soil or installing geotextile drainage mat on the exterior of the foundation wall.
• Ensure good horizontal drainage with an exterior footing drain pipe around the perimeter of the home to manage water effectively.

Compliance with Codes and Standards

ENERGY STAR Single-Family New Homes, Version 3/3.1 (Rev. 11) – National Water Management System Builder Requirements

• Water-Managed Site and Foundation.
  • Exterior surface of below-grade walls of basements & unvented crawlspaces finished as follows:
    • For poured concrete, masonry, & insulated concrete forms, finish with damp-proofing coating.
    • For wood-framed walls, finish with polyethylene and adhesive or equivalent waterproofing.
• Water-Managed Wall Assembly.
  • Flashing at the bottom of exterior walls, with weep holes included for anchored stone/masonry veneer and weep screed for adhered stone/masonry veneer or stucco cladding, or equivalent drainage system.

DOE Zero Energy Ready Home (Revision 07) – Exhibit 1 Mandatory Requirements

• Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.

EPA Indoor airPLUS (Revision 04)

• 1.3 Damp-Proofing and Waterproofing Below-Grade Exterior Walls.
  • Homes must meet ENERGY STAR Certified Homes requirements, which fulfill Indoor airPLUS requirements for damp-proofing below-grade exterior walls.

2012, 2015, 2018 IRC, and 2021 International Residential Code

• Section R406.1 Concrete and masonry foundation damp-proofing.
  • Foundation walls retaining earth and enclosing interior spaces below grade must be damp-proofed.
  • Masonry walls require a specified application of Portland cement parging.
• Concrete walls are to be dampproofed using specified methods or those listed in Section R406.2 for waterproofing.
• Section R406.2 Concrete and masonry foundation waterproofing.
  • Exterior foundation walls retaining earth below grade must be waterproofed using specified methods.
  • Exception for certain materials on unit masonry walls.
• Section R406.3 Damp-proofing for wood foundations.
  • Wood foundations enclosing habitable spaces below grade must be damp-proofed.
• Additional sections outline panel joint sealing, below-grade moisture barrier, porous fill, and backfill requirements.
• Section R403.1.4.1 outlines methods to protect foundation walls from frost, including exceptions for accessory structures.
• Table R405.1 describes drainage characteristics and frost heave potential for soils.
• Section R403.3 outlines footing requirements based on the air freezing index.
• Table 403.3(2) provides air-freezing index values for US locations.
• Retrofit requirements are specified for various IRC editions.

Retrofit: 2009, 2012, 2015, 2018, and 2021 IRC

• Section R102.7.1 Additions, alterations, or repairs.
  • Conformance to the provisions of the code for renovations without requiring compliance for unaltered portions unless otherwise stated.
• Appendix J regulates repair, renovation, alteration, and reconstruction of existing buildings to ensure continued safe use.

This comprehensive approach to damp-proofing and water management helps protect your home from moisture-related issues.