Underground Garage Drainage Membrane

Many underground garages suffer from leaking wall areas. Moisture infiltration can create unsightly staining, slipping hazards and damage to concrete walls.

Often, these leaks are caused by improper drainage solutions. To remedy this, a forensic waterproofing expert should examine the walls to document all the potential moisture migration points.

Air Gap Membranes

Air gap membranes prevent moisture in the soil from soaking through basement walls and into the concrete foundation. These membranes are typically made of a rugged, impermeable material like high-density polyethylene (HDPE). Some examples include Delta MS by Cosella-Dorken and Platon from Armtec. The latter product combines a HDPE sheet with a layer of sodium bentonite that expands when it becomes wet, sealing out ground water.

Products such as these can be used for both new construction and retrofits of damp basements, and they’re a Underground garage drainage membrane good choice for projects where backfill is impractical or impossible. They’re also useful for waterproofing retaining walls, built-up flower beds and around culverts.

These products are designed to be fast-installed and easy to work with, which can speed up basement construction. In addition, they don’t require specialized safety equipment and can be installed in any weather.

One of the most effective drainage membranes available, perforated dimple sheets are a popular choice for blindside work and tunnels. They’re also widely used for underground garage drainage in commercial and residential applications, according to the National Design/Build Institute of America (NDBIA). These sheets combine a waterproofing membrane with a geotextile in a single unit. The membrane is attached to the geotextile with fired fixing nails that are welded into the washers, creating a bond without penetration of the membrane. A drain board with an integral air gap is then placed over the membrane, followed by perimeter drains.

Perforated Drain Sheets

These plastic sheets are cuspated under heat and pressure to create a perforated drainage core with high flow rates. They’re designed to work with a wide range of base materials, and their bonded geotextile surface prevents soil particles from clogging the drain. They also have installation straps to make it easier for contractors to install them in difficult areas like curves and joints. They can be installed vertically or horizontally, and their open dimples drain away moisture from the concrete to reduce hydrostatic pressure on the membrane and foundation.

Pieter Greidanus of Armtec notes that these dimpled membranes are an ideal solution for retrofitting damp basements where excavation isn’t feasible, since they keep moisture vapor from rising to the inside of the footings and into the interior furring strips. He says that perforated drainage membranes are a good option to consider when building new homes, too, because they prevent the buildup of water around foundation walls.

When installing a perforated drain sheet, it’s important to follow the manufacturer’s installation instructions closely. Most manufacturers recommend laying a layer of filter fabric over the basement floor and then installing 4-inch PVC pipe leading down to the drain, which should be tied in with a strainer at the bottom of the pipe. A Neo-Loc gasket molded into each Zurn drain body makes it easy for installers to securely connect the drain to the underground drain line, and a compression drain head prevents the need for additional labor in sizing and installing a backwater valve.

Underseal Blindside Membrane

The 73-mil Underseal blindside membrane from Polyguard consists of a multi-component layer of chemical resistant backing laminated to a waterproofing compound and bonded to an embedded nonwoven geotextile fabric. It can be installed horizontally under the concrete slab or vertically behind a “blind-side” cast-in-place concrete wall. It protects the structure from moisture migration, and acts as a barrier to toxic contaminants like methane and radon gases.

Contractors install the membrane before workers pour the concrete foundation wall. They place it over the soil support system (such as shoring, sheet piles, rock anchors, wood lagging walls or shotcrete) and ensure that all penetrations are sealed.

Builders then cover the membrane with a suitable base and formwork. When the concrete is poured, it creates a mechanical bond with the membrane, preventing water from migrating through the gap.

When installing a blindside membrane, it’s important that the construction crew carefully follow manufacturer instructions for surface preparation and sequencing of trades. Surfaces should be smooth and firm, free of mud, loose mortar, wires, fins, metal projections or other substances that could prevent proper placement of the membrane. The permeability of the membrane should be tested using a water meter prior to the concrete pour to ensure that it is sufficiently impermeable for its intended application. During the testing, the permeability is gradually increased to 100 psi while the water meter is monitored for a rise in pressure that indicates a crack in the block face.

Polymer Grout Injection

Water-related damage can cause a lot of costly problems for parking structures. Early detection of water leaks and signs of corrosion — such as efflorescence, a powdery substance indicating the presence of moisture within concrete — can help avoid costly repairs and reduce structural integrity. Effective waterproofing methods Biaxial tensile geogrid include immediate interventions, such as sealing leaks with polymer grout injection, and long-term strategies involving regular inspections and periodic re-application of waterproofing materials.

Injection grouting uses two special water based chemicals pumped under pressure through the damaged pipe and into the soft, weak strata of voids and cracks. The grout then fills these voids and stabilizes the soil underneath, preventing future settlement of the structure.

The injection process starts by performing a penetrometer test to assess the density of the soil. Then technicians establish an injection grid that targets specific locations where the polymer will be injected. Holes are then drilled through the slab or other structural element, and tubing is inserted into each hole to inject the chemical mixture.

Once the polymer is injected, it immediately expands to fill the voids and cracks. The resulting grout is non-shrinkable and has excellent shear bonding strength. Additionally, it is extremely strong against lateral loads and can withstand the weight of vehicles. Unlike cement, this type of injection grout is also not susceptible to future failure due to the washing through of water or erosion processes.