Basement Waterproofing: Is Your Dimple Mat Up for the Job?

Proper basement waterproofing is critical to keeping foundations dry. Opting for a dimple mat for a foundation’s protection system is the right choice. Dimple mats, also known as dimpled membranes, have many advantages over other systems. They can easily be installed over virtually any foundation type: poured concrete, concrete block (CMU), insulated concrete form (ICF) or preserved wood foundations (PWF).

Waterproofing membranes for basement foundations offer many benefits that asphaltic sprays do not.

Dimpled membranes provide:

  • An even application, for consistent, predictable performance;
  • Factory-controlled quality – the quality of a spray job can differ from installer to installer; with a dimpled mat, you know what you’re getting, and;
  • The ability to bridge foundation cracks.

dimple mat drainage

This means no water intrusion, optimal comfort and healthy living spaces for homeowners, and 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 dimple mat, allowing it to flow freely to the perimeter footing drain.

How to assess your basement wall waterproofing membrane

ripped dimple mat

You choose a dimple mat based on decent specs, and the product appears to be of good quality, but how can you know if the product you’ve chosen is truly up for the job? 

When selecting a dimple mat, you should consider the following:

  • What type of protection do you believe you’re getting?
  • Do you know the best/recommended way to install or secure the dimpled membrane to the foundation?
  • What accessories are provided, and how do they affect performance?
  • Might the product sag or tear? 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 using an inferior dimpled membrane, or from an improper installation?
  • Do you know the proper recourse should an issue/damages arise?

The type of protection the homeowner can expect depends a great deal on the quality of the dimpled membrane you select. The dimple height, sheet thickness, and compressive strength vary between manufacturers. 

As is true in many industries, when it comes to building supplies, you get what you pay for. Why are some membranes cheaper than others? Because the quality is inferior.

Recommended reading…Foundations, Keeping Your Bottom Dry: Basement Waterproofing Methods with Dr. John Straube

What qualities should I look for in a high-performance dimple mat?

A mix of HDPE layers.

Choose a dimple mat with proven durability, a selection of any and all required accessories, and an in-depth installation manual.

Start with using the most durable dimpled membrane on the market. It’s common for dimple membranes for basement waterproofing to be made of thermoplastics like high-density polyethylene (HDPE). 

What’s not common across brands is the formulation and/or composition of the dimple mat. Using all-recycled HDPE saves cost and makes the product “green,” but also makes the membrane more vulnerable to aging and stress-cracking, which leads to collapsing of the dimples and failure of the foundation protection. 

To prevent that, a co-extruded dimple mat with an embedded layer of recycled HDPE between two outside layers of new HDPE is the best option. This mix gives the membrane a higher stress-crack resistance and compressive strength, and helps to maintain the membrane’s integrity and durability, meaning you don’t have to worry about sagging or tearing, which leads to basement moisture intrusion.

Easy installation.

Speaking of sagging and tearing, there are a couple of ways these can occur with a dimpled membrane. Proper installation is your first move in preventing sagging and tearing. With a dimpled membrane, installation can be done as soon as the forms are removed. The weather won’t dictate when you can apply it, since it’s not temperature dependent.

Compatible accessories that contribute to performance.

Fasteners – and their placement – make a big difference in membrane installation and functionality. 

Using a multi-stud fastener over single-stud fasteners provides advantages such as superior holding power to prevent tear-down at fastening points during backfill. Once the membrane is rolled out along the wall, be sure to install the fasteners at appropriate intervals. 

For rolls greater than 7’ (2 m) in height, an extra row of fasteners is suggested in the middle of the dimple membrane.

What’s the best dimple mat option for basement waterproofing today?

DELTA®-MS is the dimpled membrane others try to imitate. It’s the industry standard. In an apples-to-apples comparison, building professionals will choose DELTA®-MS. And because of this, the only way for imitators to sell their product is by downgrading quality in an attempt to gain some edge; typically, in pricing. 

But it is that very edge that ends up costing the consumer so much more in the long run. Downgraded products provide downgraded protection – and can downgrade your reputation as a builder.

delta-ms foundation protection system

The DELTA®-MS foundation protection system is the most durable dimple mat on the market, keeping foundations dry for the life of the building. It is a co-extruded product, made of 60% recycled and 40% new materials – recycled material inside and virgin HDPE layers outside. All three layers also contain specific additives to protect the polymer against aging from elements such as oxidation and UV.

DELTA®-MS is also supported by an extensive certified-installer program. This certification provides the confidence, reliability, and trust to ensure 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 on the basement waterproofing membrane.

Learn more about basement waterproofing and foundation protection at the DELTA® Academy: