Negative-side waterproofing 101 - Construction Specifier (2024)
by Harry Lubitz, CSI, CDT
While negative-side waterproofing is not the usual first choice in new construction of foundations, it clearly has its place. It is often selected as the last resort when other options (positive and blind sides) are impractical. Often, negative-side waterproofing is better than re-excavating the entire structure when the original waterproofing materials fail and water is actively leaking.
When positive-side and blindside waterproofing are applied, water under hydrostatic pressure would not permeate the foundation and the building is expected to remain dry for life. Unfortunately, this is not always the case, and the solution either involves excavating the foundation to conduct repairs or retrofitting the insides of the wall with a negative-side waterproofing application.
Negative-side waterproofing is the application of a coating material to the interior or the ‘dry’ side of a foundation or wall. Its primary function is to create a barrier coat to stop water from leaking through the wall and keeping the space dry.
Negative-side waterproofing can also help offer a secondary function of providing a decorative surface that offers a value above and beyond a coat of paint. It makes the foundation space more attractive and livable, while serving to keep water out.
All foundation coatings, including negative-side applications, must be impermeable and withstand hydrostatic pressure, the force exerted in every direction on a foundation. Standing water exerts approximately 3 kPa (0.43 psi) for every foot of water. Consequently, the significant force created by the water will find its way through the foundation wall and into the (formerly) dry space.
Negative-side waterproofing materials typically fall into two categories:
penetrating liquid acrylic waterproofing materials sealing voids and capillary openings where water seeps through; and
cementitious surface coatings providing a secondary cement-based barrier.
Penetrating liquid acrylic waterproofing materials have expanding polymer or crystalline additives as part of their chemistry. On application, these additives expand or grow to block the water-invading pathways. Cementitious surface coatings rely on the applicator to ‘push’ the product into the pathways, and then the product hardens to create a barrier.
Negative-side waterproofing has clear advantages. It can be installed with full visibility and can be easily repaired. It can be applied any time after the substrate material has cured. It can be applied with minimal training and is usually cost effective. Unfortunately, since it is installed from the inside of the structure, the substrate material is not waterproofed, and therefore, unprotected from corrosive soil materials or freeze/thaw cycling.
Negative-side waterproofing does have its limitations. It requires secondary assistance when the substrate has cracks larger than 1.5 mm (1/16in.) or actively flowing water leaks. In these circ*mstances, hydraulic cement is the recommended course of action. Hydraulic cement is a more modern invention with unique properties and several advantages.
First, hydraulic cement is easy to mix with clean water and can be troweled into any shape. Second, it expands on curing and will seal static cracks up to 19 mm (¾ in.) wide and/or deep. Third, it will work to plug actively flowing water. Finally, it sets quickly (within three to four minutes) using cold mixing water—warm mixing water accelerates the set time and reduces working time. Using hydraulic cement to tool joints between floors and walls is also a recommended practice. It is important to note hydraulic cement will not stop moving (dynamic) cracks.
Care should be exercised when using hydraulic cement as it is Portland cement based. Proper personal safety equipment, such as eye protection, rubber gloves, and a National Institute for Occupational Safety and Health (NIOSH)-approved respirator, should be used. Breathing Portland cement dust is a health hazard. Some heat is also generated during the chemical reaction with water, therefore, it is best to avoid skin contact with the material.
Called negative-side waterproofing, this technique involves applying product to the dry or inside face of the surface. Negative side waterproofing prevents water from entering occupied space, but it does not prevent water from entering the substrate.
Mix the negative pressure membrane with water or with liquid supplied, use a mechanical mixer to ensure an even mix. 3. Wet or moisten the wall area to be waterproofed, then apply a coat of membrane to the wall and extending the membrane onto the floor by 100mm min.
Negative side waterproofing does not provide protection from freeze-thaw cycles and is limited to the application of cementitious systems. Water-resistant and waterproof building materials cost more than standard products, and installation might be more expensive as well.
Negative-side waterproofing is normally done when there is an existing wall and there's no way to get access to the outside (positive-side wall) to waterproof it. A typical example where this situation plays out would be with an existing below-grade, occupied space in a high-rise building in any downtown area.
Unequal sharing of electrons makes water a polar molecule.
This means that electrons spend a bit more time at the oxygen end of the molecule. This makes the oxygen end of the molecule slightly negative. Since the electrons are not near the hydrogen end as much, that end is slightly positive.
Retaining walls require careful planning and engineering to ensure they are strong enough to hold back the soil. Another disadvantage of retaining walls is that they can be difficult to maintain. Retaining walls can be susceptible to erosion, cracking, and other types of damage.
Incorrect installation methodology can lead to leakage issues. Correct installation is key when it comes to waterproofing. Many leakage problems are caused by poor waterproofing, which can result in moisture. If the waterproofing is done incorrectly, the building can degrade much quicker due to the moisture build up.
Cement-based waterproofing is the easiest waterproofing method used in construction projects. It is easy to apply by mixing cement-based waterproofing materials. This method is generally used in areas that are in the interior of the building and have high contact with water, such as toilets and bathrooms.
Poor waterproofing can fail, leading to cracks, mould issues, and structural defects like concrete cancers. Failure of your waterproofing can cause safety issues, significantly reduce the value of your property, and lead to unfitness for occupation.
These include health hazards; such as asphalt fumes, lead, silica, and solvents; as well as safety hazards, such as falls from elevation, awkward and heavy lifting, flammables, and power tools.
Negative-side waterproofing is the application of a coating material to the interior or the 'dry' side of a foundation or wall. Its primary function is to create a barrier coat to stop water from leaking through the wall and keeping the space dry.
Depending on the structure and need, the waterproofing membrane can either be applied to the interior (negative side) and, the exterior (positive side), or in places inaccessible by people (blindside).
Polyurethane liquid membrane waterproofing is used for flat roof areas exposed to weather. This method of waterproofing is costly. Polyurethane Liquid Membrane may provide greater flexibility.
Waterproofing significantly enhances the durability of structures. By creating a protective barrier against water, it shields concrete and masonry materials from moisture-related degradation. This prolongs the lifespan of the structure, reducing the need for frequent repairs and replacements.
The inhalation of the fluorinated compound resins used as a water repellent is known to cause acute lung injury (ALI) (2) . ... ... Waterproofing sprays used in a closed room often cause respiratory symptoms such as coughing and dyspnea, even when used for only a short duration (1) (2) (3).
Introduction: My name is Errol Quitzon, I am a fair, cute, fancy, clean, attractive, sparkling, kind person who loves writing and wants to share my knowledge and understanding with you.
We notice you're using an ad blocker
Without advertising income, we can't keep making this site awesome for you.
