Building a Dry Basement: 3 Key Construction Considerations

Building above grade is tough enough, but below grade? It is the most difficult space to get right. Not only does a basement hold the building up; it must keep groundwater, soil gas, and water vapor out, while keeping heat in during the winter and out during the summer. Once moisture has seeped into the wall assembly, it becomes a challenge to treat the problem, making basements even more vulnerable to mold, since they are often already damp and humid.

Common Basement Problems:

• Water leaks
• Dampness
• Rotting of building components
• Elevated relative humidity
• Poor air quality (bad smells)
• Soil gas infiltration (e.g. radon, methane)
• Low energy efficiency (thermal bridging or poor insulation of walls and floor)

Quality homebuilding begins and ends with utilizing the best products and building practices right from the start. This is a job that should only need to be done once.

With that in mind, consider these three factors for long-lasting basement wall waterproofing.

1. Keeping Basements Dry with the Right Dimpled Membrane

A dimpled membrane offers many benefits that sprays simply do not. Dimpled membranes provide an even application, factory-controlled quality, and the ability to bridge foundation cracks.

This eliminates water intrusion and provides optimal comfort and healthy living spaces for homeowners, resulting in fewer warranty claims and call-backs for builders. The dimples also create an air gap between the membrane and the foundation, which removes hydrostatic pressure from any incidental water getting behind the membrane, allowing it to ­flow freely to the perimeter footing drain.

You choose a product based on project requirements, specs, and apparent good quality, but how can you know if the product you’ve chosen is truly the best way to waterproof a new foundation?

When selecting a drainage membrane for basement wall waterproofing, you should consider the following:

• What type of protection do you really need?
• What type of protection do you believe you’re getting?
• Do you know the best/recommended way to install or secure the drainage membrane to the foundation?
• What accessories are provided, and how do they affect performance?
• Might the product sag, tear, or collapse? How do you avoid this?
• Would you recognize the signs of a problem with your foundation protection?
• Do you know the damages that can result from a failed drainage membrane, or from an improper installation?
• Do you know the proper recourse should an issue/damages arise?

The type of protection homeowners can expect heavily depends on the quality of the drainage membrane you select.

The dimple height, sheet thickness, and compressive strength vary between manufacturers. Understanding the true requirements for the project will allow you to distinguish the appropriate performance criteria, and in turn select the appropriate drainage board.

Dimpled Membrane Application

The DELTA®-MS foundation protection system maintains an air gap that keeps moisture and damp soil away from the foundation. The below-grade dimpled membrane is impermeable to both water vapor and liquid water. As a result, it maintains a complete capillary break between ground moisture and foundation walls. The innovative, high-compression design offers reliable protection to foundation walls as deep as 12 ft below grade.

Unlike sprayed-on coatings, DELTA®-MS successfully bridges big cracks and other imperfections in foundation walls that inevitably appear as settling occurs. For extra protection, DELTA®-MS can also be used in combination with sprayed-on systems.

Waterproofing or dampproofing are not required behind DELTA®-MS:

• DELTA®-MS is approved as a stand-alone system
• DELTA®-MS may also be applied over other dampproofing or wall waterproofing systems

Building code requirements vary by country. More specifically, Canada requires below-grade drainage while the U.S. does not.

DELTA®-MS meets building code requirements outlined by both countries in one, easy-to-install product. If U.S. builders and installers select it, they will end up beyond code by adding the drainage component as well as wall waterproofing, though only wall waterproofing is required by IRC.

If it’s known to be the appropriate approach based on building science knowledge, the right solution is to always increase your building standards – even if that means you’ve exceeded building codes.

2. The Right Fastener Matters

A good fastener resists tearing when all of the downward pressure from the settling soil is focused on a single nail.
Since nails are one of the most expensive individual components, the DELTA®-FAST’ner was developed based on the need for better holding power. Fewer nails are required for superior hold, with the load spread amongst five dimples (four nubs, plus the center with the nail), eliminating tear-down during backfill and seasonal thaw.

Other installations allow washers to be installed on the top flat tab of their drainage boards every 6”-8”. Sometimes they may be put incorrectly at wider intervals, allowing the dimple space next to the wall to fill with dirt and stop water from draining. Some will wrongly argue this doesn’t matter, as they are spraying the wall with asphaltic dampproofing behind the drainage board.

This is inadequate building practice.

Firstly, one loses any capillary break with this installation method. Wet soil is directly against the wall. Secondly, liquid water can begin to pool above the accumulated debris, creating hydrostatic head. Spray-on asphalt doesn’t resist the passage of water under hydrostatic pressure. This means wet concrete and capillary action. If this pool happens near a crack, which the spray-on asphalt cannot span, then you will get liquid water ingress (otherwise known as a leak).
Do not make this mistake. Following manufacturers’ recommended installation method is the best way to ensure a products performance and longevity. 

To avoid damage, do not install DELTA®-FAST’ners within three inches of corners.

3. Certified Installers 

Experienced homebuilders understand how much work goes into building a good reputation, getting referrals, and growing their business. They also know just how quickly a bad experience for the homeowner can undo all of that hard work.

Proper below-grade moisture management is your first step in building a dry basement, keeping your reputation and your homes going strong.

DELTA®-MS is supported by an extensive certified-installer program. This certification provides buyers the confidence, reliability, and trust to ensure their materials are properly applied, and buildings are properly protected. The certified-installer program allows builders and contractors to provide customers a 5-year leak-proof warranty and 10-year material warranty.

For more information and tips for creating an interior drainage solution, download the complete guide to protecting foundations.