Dimpled membrane is available as one simple and tasteful way to lower the chance of moisture-related issues in basement. As you may have known already, damp basement is a common complaint of many homeowners and it is not an easy issue to resolve. The material itself comes in the form of mat installed on the outer side of the basement walls.
Dimple sheet is a protective member with waterproof characteristic that is responsible to prevent excess moisture in basements and reduces hydrostatic pressure against foundation. Dimple matting can be used both vertically and horizontally, but the formerly mentioned installation position is more common, as it is often used as a solution for various drainage situations. Aside from being used for residential basement, it can be found in major commercial projects stretching 50 ft under the ground as well.
The mat sheet is made of partially rigid plastic, typically polyethylene with high density in roll form. The plastic has a texture that visually looks like egg carton, consisting of protruding dimples that adds to its thickness. Speaking of thickness, it generally comes as ¼ to ½ inch thick layer.
As the dimpled membrane is installed against the basement walls, the plastic protrudes from the walls due to the dimples, allowing an air space for free draining between the walls and the plastic. Water that enters this space flows easily to the bottom of the sheet while picking up tiny particles of soil and water. Both these elements will accumulate and increases the weight against the foundation, but the membrane will protect the sheet from creating sediment clogging.
Despite being relatively thin, it’s impressive that the dimpled membrane for basement walls can get water to move efficiently. Dimple mat offers the same function as chunky gravel only in a fraction of an inch.
For parking garage or plaza decks types of application, the mat is installed on top a waterproofing layer with the dimples face up, then the final layer is set on top of the geotextile. Water will be directed by the membrane to the slab’s floor drain when it penetrates through the concrete deck’s cracks or pavers.
On the other hand, horizontally installed dimpled mat that involves vegetation typically has the dimples section faces down. The dimples will “cup” water like a retention layer during drought or dry season, and allow excess moisture to get to drains during wet season. Horizontally installed dimpled membrane can be found under sport fields, golf courses, or green roofs.