Introduction

Concrete slab floors, prevalently used in residential and commercial constructions, are susceptible to water absorption. This can lead to structural problems over time, including but not limited to, cracking and dampness issues. This article provides detailed insights into effective methods for preventing water absorption in concrete slab floors, ensuring longevity and durability.

Understanding Water Absorption in Concrete

Concrete, being a porous material, can absorb water, which can lead to issues such as cracks, spalling, and even structural damage. Proper waterproofing of a concrete slab floor is crucial to maintain its integrity and prevent these problems. There are various methods to achieve this, including the use of specialized membranes and sealers.

Types of Waterproofing Methods for Concrete Slabs

Brushable Membrane Coatings

There are several chemistries available for brushable membrane coatings, including Acrylic, Cementitious, Acrylic PU (Polyurethane), and Polyurea. These coatings form a protective barrier on the surface of the concrete, preventing water from penetrating.

Prefabricated Membrane Sheets

For larger areas, prefabricated membrane sheets such as APP, EPDM (Ethylene Propylene Diene Monomer), PVC (Polyvinyl Chloride), SBS (Styrene Butadiene Styrene), and HDPE (High-Density Polyethylene) are effective. These sheets create a continuous layer that covers the entire surface of the concrete slab, forming a robust barrier against water infiltration.

Installation Techniques

Installing Waterproof Membrane from the Underneath

For new construction or renovation projects, installing a waterproof membrane from the underside before placing the slab is the most effective method. This ensures that the entire slab is protected from water leaks and structural cracking. Proper termination of the membrane at its edges is crucial for maintaining its effectiveness.

Waterstops for Joints

Waterstops should be installed in all joints to prevent water from seeping through. In smaller areas like bathrooms or under showers, a membrane can be applied under tiles. This requires careful application and is typically more complex than other methods.

Alternative Sealing Methods

Sealing a concrete floor that also acts as a foundation slab can be achieved through several techniques. These include:

Placing a Water Barrier: Installing a barrier beneath and along the sides of the slab where it meets the walls can help prevent moisture from entering the concrete. Mixing Concrete with Latex or Polymer: Adding a latex or polymer composite to the concrete mix during construction can significantly reduce water migration through the concrete. Bituminous Coating: Lining the sides with a bituminous coating can create an effective moisture barrier. Placing Footing Drains: Installing footing drains under and along the sides of the slab can help manage drainage and prevent water from accumulating beneath the concrete.

Sealing Techniques for Thicker and Thinner Concrete Slab Floors

The method for sealing a concrete slab floor can vary based on its thickness. For a concrete slab thicker than 200mm:

Chip off concrete around 100mm and remove all debris. Clean the surface thoroughly. Spread a polyethylene sheet of 1000 to 1200 micrones over the area, ensuring joints and laps are at least 200mm apart. Over this, lay waterproof concrete.

For a concrete slab that is only 100mm thick:

Break and remove concrete and debris. Clean the area thoroughly. Follow the above procedure using the same steps to seal the slab.

Conclusion

Preventing water absorption in concrete slab floors is crucial for maintaining their structural integrity and longevity. Whether you opt for brushable membrane coatings, prefabricated membrane sheets, or alternative sealing methods, proper application and maintenance are key to achieving waterproofing effectiveness. By employing these techniques, you can ensure that your concrete floors remain in excellent condition for years to come.