Why is Dimple Board So Effective for Wall Drainage?

The long-term integrity and health of a structure depend on a successful wall drainage system, which includes three components:

  • A dimple board waterproofing (drainage boards, drainage panels) that gives moisture a path to the footings.

  • A footing drain to collect water, and direct it to a sump pump.

  • A pump to remove water to an external stormwater collection system. Alternatively, a sloping lot may provide enough gravity from the footing drain to the sunlight.

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What is a Dimple Board?

Semi-rigid, three-dimensional dimple boards for waterproofing, as part of the drainage wall system, are sold as rolls. Dimple boards help keep the below-grade wall moisture-free, to protect the structure’s integrity, immensely reduce long-term maintenance and repair expenses, and help to prevent the following below-grade moisture-related issues:

  • Humidity in the basement or crawlspace that can lead to structurally damaging and unhealthy mold

  • Cracks in walls

  • Inward or outward bowing walls

  • Crystalline deposit of salts (efflorescence) on a crawlspace or basement floors or walls

  • Unpleasant smells and diminished air quality in the basement or crawlspace

What is a Dimple Board for Wall Drainage?

High-quality below-grade walls dimple boards, like the Polyflow® Drainage family of products, contain dimples that stick up like small mounds, to promote the flow of water away from a foundation and the building site and stop water and harmful contaminants from entering the building. The dimples also keep the soil away from the poured concrete wall, to prevent water intrusion by hydrostatic pressure.

Why Do Foundations Need a Dimple Board?

Below-grade foundation dimple boards provide an essential component to keeping a building’s foundation dry and managing a building’s integrity and health. They also help control repair and maintenance costs due to moisture intrusion. Specific benefits of dimple boards include:

  • The tight bond between the dimple board and foundation creates no space for water, insects, or contaminated soil vapors to enter the structure, which helps to protect the foundation’s integrity and avoid expensive maintenance and repairs.

  • Dimple board drainage systems relieve hydrostatic pressure and extend below-grade waterproofing membrane lifespan.

  • Watertight dimple boards provide an efficient and cost-effective drainage plane and protect a foundation from water intrusion.

  • Dimple boards eliminate the need for costly full-height gravel.

  • In Canada, dimple boards meet the dual code mandates for drainage and dampproofing. While the U.S. does not require a drainage layer around the foundation, it will significantly benefit areas with soil moisture.

Keeping a foundation dry must include other components besides a dimple board: proper site selection and grading, and applying a high-quality below-grade waterproofing membrane, like Polyguard below-grade waterproofing.

Dimple Boards vs. Spray-Applied Products

Dimple sheets offer contractors and building owners several advantages over spray-applied products, to save both time and money:

Benefits to Contractors

  1. Installing dimple boards only requires a nail gun (or a hammer) and a sharp knife.

  2. Installing dimple boards does not require expensive breathing filters and safety equipment associated with spray-applied solvent-based products.

  3. Installing dimple boards does not require large and costly spray rigs like spray-applied products.

  4. Builders can quickly install dimple boards at a rate of about 130 linear feet per hour.

  5. Builders can install dimple boards in any weather, to extend the working season. Fluid-applied membranes require dry surfaces and above-freezing temperatures.

  6. Dimple boards span cracks on concrete foundations more effectively than fluid-applied members, to reduce callbacks, eliminate wasted time and profit, and prevent unhappy customers.

  7. Dimpled boards resist the abuse of standard backfilling. In contrast, during installation, fluid-applied membranes require an additional protection course.

Benefits to Building Owners

  • Dimple boards promote drainage, unlike spray-applied products.

  • Dimple boards span the unavoidable cracks in concrete foundations, unlike spray-applied products.

  • Dimple boards remain stable for the structure’s lifetime. Over time, many fluid-applied membranes dry out, oxidize, and crack.

  • Dimple boards last 50 years. Based on the soil's chemicals, tar membranes will degrade in three to five years.

Installing a Dimple Board

For optimum performance for the lifetime of the dimple board, builders must install dimple boards according to the manufacturer's instructions. For help and tips on installing below-grade dimple boards, don't hesitate to contact the Poly Wall® building professionals.

Builders can install dimple boards vertically or horizontally, depending on the application:

  • Vertical applications provide below-grade hydrostatic pressure relief over the foundation, planter, and retaining walls.

  • Horizontal applications include plaza decks, flat slabs, foot pavers, planter boxes, etc.

Generally, builders install dimple boards according to these steps.

  1. Clean the wall and apply waterproofing or required insulation.

  2. Place the membrane, dimples facing the wall, to the base of the footer to guide the water directly to the perimeter drain and away from the wall/footing cold joint, keeping the membrane smooth.

  3. Mechanically affix (with screws, bolts, or liquid adhesives) dimple boards around the entire exterior of a poured concrete foundation, from the base to the final grade height (where you can visibly see the finished foundation). While the fasteners puncture the membrane, they don't interfere with the board's performance due to a lack of hydrostatic pressure to force water through the openings.

  4. Place plastic molding at the top of the dimple board and around window openings to prevent water and debris from building up behind the dimple board, which can lead to clogged dimples and wet soil against the concrete wall.

Polyflow® Offers The Best Dimple Board Options

Polyguard Architectural Products designed the Polyflow® Drainage family of products to provide our customers with various solutions for lightweight below-grade drainage. In addition, our high-capacity, easy-to-install drainage products can decrease excavation needs.

Builders can use the Polyflow® Drainage products with our engineered sheet and liquid membrane products.

Polyflow® Drainage products provide many options to fit the needs of your waterproofing system:

  • Products with comprehensive strengths of 15,000 and 21,000 psf

  • Products for vertical or horizontal installation

  • Products with a high-strength Polymeric film on one side and products without the film

Polyflow® 10, 10P, 15, and 15P SHEET MOLDED DRAINAGE MATS

Builders vertically apply Polyflow®, 15, 15P 10, and 10P Sheet Molded Drainage Mats over Polyguard waterproofing membranes. The mats direct water into the drain core while minimizing the flow of soil, which can clog the core. In addition, Polyflow’s® 10, 10P, 15, and 15P drainage mats, with a compressive strength of 15,000 psf, can limit hydrostatic pressure when attached to our high-capacity collector and outlet drainage product, Totalflow™.

Polyflow® 18 DRAINAGE MAT

For horizontal applications, the design of lightweight Polyflow’s® 18 is a high-capacity drainage system that works with our engineered sheet and liquid membrane products used for below-grade waterproofing applications.

The lightweight and simple-to-install Polyflow® 18 drainage mat supplies a compressive strength of 21,000 psf, able to handle the most complex horizontal applications. Additionally, this product uses a woven filter fabric specifically for concrete pours to allow flow under loaded conditions.

Why Choose Polyguard Dipple Board Wall Drainage Solutions?

A foundation’s quality plays a significant role in a building’s performance and longevity. If you improperly design and install the foundation, particularly the below-grade drainage and systems, severe building integrity problems will happen. To avoid expensive repairs due to below-grade leaks, always select high-quality dimple board drainage solutions like Polyguard products, along with our below-grade waterproofing membrane systems.

Don’t hesitate to contact a Polyguard professional today for questions concerning below-grade dimple board drainage solutions and other waterproofing systems.