Changes to material technology in the construction industry have always been conducted at an extremely slow pace. Material selection was often based on price and reliability, making it difficult for technological advancements to break into the market. This sentiment was particularly true in the roofing and waterproofing industries—where hot bitumens (coal-tar and asphalt) were material mainstays for two centuries. Even though the influx of modified bitumens and single-plies (thermosets and thermoplastics) entered the U.S. commercial market in the 1980s (over 35 years ago) they are still referred to as ‘newer’ materials in some circles. New material technology was stagnant between the 1980s through the late 1990s as the focus was on improvements and/or corrections to existing technology.
This all changed in the late 1990s.
There have been continual advancements in construction material technology since the late 1990s. These changes have been prompted by the same industry-wide concerns that have defined the 21st Century to this point; labor shortages, environmental concerns, health and safety concerns, economics and the ever-increasing requirement by building owners that materials and methods are sustainable.
These changes are all a result of three sentinel events that occurred in the 1990s:
- The Energy Star Act: In the mid-1990s the EPA developed a program that recommended energy savings for products in all industries. The effect in the roofing industry was the initial recognition of reflectivity rates for roof surfaces. Although the Energy Star Act was not adopted as code, it began the discussion of reflectivity rates for roof surfaces and it was eventually broadened to include emissivity rates when it was added to LEED requirements. It forwarded the sustainable material technology movement and led to energy savings and sustainability regulations. Sustainable technology is now a mainstay in construction materials and has overtaken price as the key determining factor that building owners base material selection on.
- Labor Shortages: Rich Karlgaard of Forbes magazine reported in his July 26, 2016 column that while speaking to a trade group of top construction company CEOs and CFOs he found their top concern was not “taxes, regulations, the slow-growth economy…it was the lack of skilled labor.” Since the mid-1990s there has been a significant drop in labor participation in all construction trades with the largest impact in roofing/waterproofing trades. The lower work force levels have contributed to the advent of materials that can be applied with smaller crews.
- Safety and Health Concerns: In the late 1990s the top insurance carriers discontinued providing policies to roofing/waterproofing contractors that completed system applications with open flames or torches. Around the same time, more building owners were refusing the use of hot applied built-up roofs due to fumes associated with these applications. Fiberglass insulation and asbestos-containing materials were discontinued for use in commercial applications because of health concerns. The focus became the health and safety of the construction workers and building occupants. Today, safety is the paramount issue in construction with only those materials and application methods that pose no health or safety risks to the applicators or building occupants approved for use.
In the past decade, the most significant improvements in material technology in the roofing and waterproofing industry have been to coatings and adhesives. The focus of development of the adhesives has been for attachment of materials that were traditionally applied with hot bitumens. The initial manufacture of cold-applied adhesives was smaller, niche manufacturers. However, by the mid-2000s, all of the major material manufacturers offered cold applied materials. The initial use of cold adhesives was in the attachment of modified bitumen membranes and insulation. Single-ply membranes have been adhered with cold adhesives since their inception in the 1980s. Today, cold applied materials are widely used for attachment—insulation to substrate, insulation to insulation, membrane to insulation—in all roofing and waterproofing applications.
Cold applied adhesives and coatings were also used for roof repair/restoration. This was not a new concept as some materials had been on the U.S. commercial roofing/waterproofing market for over 50 years at that time. They were mainly niche materials comprising of less than 5 percent of the annual U.S. market. The materials were primarily used for repairs and restoration in cold process systems that utilized cold adhesives (such as SEBS) with multiple layers of reinforcements set in shingle (BUR) fashion. While these products were effective, they were time-consuming and costly compared to other repair methods. One shortcoming of the adhesives was that they did not have the ability to perform as a waterproofing membrane without multiple application methods and inclusion of reinforcements.
Liquid Applied Rubber Membrane System
Fluid applied membrane systems have been available on the U.S. commercial waterproofing market for many years. The systems most frequently applied were hot-applied emulsions with or without reinforcements. The materials faced similar constraints as bitumen-based built-up roof systems for health and safety issues, particularly when used in tight, constrained areas, where a large portion of below grade waterproofing is required to be applied.
In 2006, a liquid rubber membrane system was developed that could be applied in cold-process fluid applied applications. The liquid rubber material combines the elastic properties of rubber polymers with the weatherproof/waterproof characteristics of a highly refined emulsified asphalt. The resulting formulations are proprietary materials that form a properly adhered monolithic, seamless, rubber membrane. The resulting membrane can be applied to range from 20 mils to 200 mils dry.
Unlike coatings that only provide a film surface or adhesives that require reinforcements for waterproofing capacity, the liquid rubber forms to a monolithic, seamless membrane that provides instant waterproofing/weatherproofing capabilities. The material cures within seconds to 80 percent of its full strength with full cure within 12 hours of application.
The liquid rubber membrane is manufactured at the point of application through its dual component formulation; the system consists of a spray grade and a catalyst that are mixed together at application through specially designed spray rig equipment. The chemical reaction between the spray grade and the catalyst results in an instant seamless rubber membrane. The instant set allows the seamless membrane to be in direct contact with water immediately. This feature also allows for the material to be applied either horizontally or vertically up to 200 mils thick in one application. Although the membrane still requires time to fully cure, it is approximately 80 percent cured when the two materials come into contact. This is a unique feature of the material and it requires specialized equipment and training to be applied correctly.
Advantages of Liquid Rubber Membranes
Liquid rubber membranes combine the properties of adhesives and coatings while adding significant technological advancements that create an instant-setting waterproofing/weatherproofing membrane. It is the twenty-first century version of a built-up roof system that has the performance characteristics of modified bitumen and—because it is a monolithic, seamless membrane—it provides longer service life with less maintenance than single-ply systems. Liquid rubber membranes provide economical solutions to all waterproofing/weatherproofing applications with superior performance characteristics.
Liquid rubber membranes can be applied in all types of waterproofing, roofing and exterior envelope conditions. The primary advantages of the material are as follows:
- Superior elongation and recovery of 1,000 percent or more: structures move. Surfaces expand. Seasonal temperature changes alter the size and shape of every object. Liquid rubber membranes have the capacity to stretch and recover, which allows for movement of the underlying surface. The material recovers to 90 percent of its original state after elongation.
- Excellent adhesion: liquid rubber bonds to most substrates and forms a permanent bond with itself resulting in self-healing and self-sealing properties. The liquid rubber membrane provides excellent adhesion to metal, wood, plastic, and concrete—even ‘green’ concrete. It also provides strong adhesion to existing construction materials like built-up roofs, modified bitumen, thermosets and thermoplastic membranes, and all waterproofing materials. In most cases, no prime or tack coat is required.
- Sustainable and environmentally responsible: the materials contain no VOCs and satisfy EPA regulations and environmental concerns. No special ventilation is required as the material is non-toxic, odorless, and non-flammable.
- Safe applications: the material can be applied with trowels, squeegees or a specially designed dual-component spray rig. No heat, kettles, torches or open flames are required in the application process. The material is safe to apply and possess no health risks to the applicators.
- Warranties: 10- to 25-year warranties are available.
Another primary advantage of the Liquid rubber membrane system is that the material is manufactured directly at application and it is self-leveling. This allows the membrane to conform to substrate irregularities and provides a continuous seal at penetrations, which are typically difficult details in waterproofing applications. The instant, full adhesion of the membrane allows for continuous system application without additional components that would be required with other membrane applications. This eliminates the chances of deformation from the breakdown of different material system components. It also eliminates most of the application areas associated with multi-component systems.
Deformations of one of the materials in the multi-component system can lead to failure of the total system. Examples of typical defects in roofing/waterproofing systems are: loss of attachment from improper adhesive application at substrate, insulation or membrane; improperly aligned insulation; loss of attachment of insulation due to substrate irregularities; voids in membrane attachment that lead to blisters/ridges; and slumping or buckling flashing from improper attachment. Improper attachment of one component leads to differential movement in the system.
The inherent properties of liquid rubber membranes provide superior capabilities for all waterproofing/weatherproofing applications. The membrane is manufactured at application and forms to a monolithic, seamless membrane. This eliminates the most vulnerable point of rolled membranes for moisture infiltration: the seams. The superior adhesion characteristics to all types of substrates and materials also eliminates the chances of moisture infiltration under the membrane.
The elongation and flexibility of liquid rubber membrane exceeds industry standards. The average elongation is over 1,000 percent and the material has the inherent ability to recover to 90 percent of its original form after elongation. This allows it to withstand typical thermal cycling and it performs in extreme cold/heat conditions. Application temperatures are wider than most other adhesives and coatings and range from ambient outside temperatures of 20 degrees Fahrenheit to over 100 F. The membrane is naturally UV resistant and can be exposed throughout the lifetime of the membrane. The membrane is compatible with all types of reflective coatings if application is required. Granule surfacing can also be applied.
The membrane is also very durable. Depending on applied dry mil thickness, the membrane can withstand heavy force and is puncture resistant with self-healing and self-sealing properties.
The membrane can be applied over damp surfaces and it can be exposed to ponded water in unlimited duration. The material has been used as pond liners and in containment tanks since its initial inception into the market. The water absorption rate is less than 1 percent—well below ASTMs minimum water absorption rate of waterproofing materials, which is 5 percent.
Advantages of Liquid Rubber Membranes for Applicators
There are significant benefits to applicators of liquid rubber membranes. The foremost benefit is the reduced crew size required for application. This is paramount due to the severe labor shortages affecting the construction industry. In the September 23/October 3, 2016 edition of Engineering News Record there is a report that states the Associated General Contractors of America (AGC) has found two-thirds of construction firms are having difficulty filling construction trade positions. In the article, it is stated, “Shortages are the most severe in the Mid-west, where 77 percent of contractors’ report difficulties in hiring, followed by the South with 74 percent, the West with 71 percent and the Northeast with 57 percent of contractors having trouble filling hourly positions.”
Stephen Sandherr, CEO of AGC, recently told ENR, “many firms have gone from worrying about not having enough work to not hiring enough workers.”
Liquid rubber membranes can be applied with a sharply reduced crew over conventional membrane systems. In most cases, a crew of three properly trained and experienced applicators using one spray rig can complete up to 10,000 square-feet in one day. Additional hoses and/or spray rigs can double and triple those production rates.
In addition to the advancements in material technology, there are vast improvements to the specialized equipment used in the application process. The spray equipment is now portable and can be transported to construction sites without heavy trucks and covered trailers. The spray equipment is also lightweight and can be easily positioned on roof areas or waterproofing trenches. This equipment is housed on four wheel carts for easy transport throughout the construction site.
The spray equipment consists of a high-volume, low-pressure system. The spray equipment was designed to be used with liquid rubber components of spray grade products and a catalyst. The dual component equipment mixes the two components outside the gun and with the appropriate materials forms a monolithic membrane upon impact with the substrate.
The equipment has a direct drive system to eliminate down time associated with traditional belt drive systems. The application rate averages up to 1,000 square-feet an hour for one gun. The equipment can run two guns at the same time, which increases production to 2,000 square-feet per hour. It can run up to 600 feet of hose and the material can be contained in everything from a 5-gallon pail to a 275-gallon tote. The most common material containment is 55-gallon drums.
The spray guns have improved also. Advancements in manufacturing have eliminated most of the clogging issues that plagued spray guns in the past. The spray guns are more manageable, light-weight and can be disassembled rapidly if material clogs occur. The older spray guns took up to an hour to take apart in the event of material clogs—losing valuable production time.
Overspray—a continual problem on most spray applications—is minimized in liquid rubber membrane applications because it is a low-pressure application and the material cures instantly after release from the spray gun. Precautions, such as coverboards, should still be set at perimeter building locations and application should not be attempted in accelerated wind conditions, but the chances of excessive overspray are minimal.
Uses of Liquid Rubber Membranes
Because of their waterproofing/weatherproofing capacity, instant cure set, adhesion success with most substrates and materials, wide-range of application temperatures and membrane mil thickness that can range from 20 mils to 200 mils dry, liquid rubber membranes can perform in most building exterior applications.
Waterproofing Applications
Liquid rubber membrane systems are ideal for all waterproofing applications—above grade and below grade. In addition to the benefits of a monolithic, seamless membrane, liquid rubber membranes possess the most important characteristics of a waterproofing membrane:
- It is a fully functional membrane and waterproof within seconds of application
- Dry mil thickness can range from 20 mils to 200 mils
- Can withstand constant emersion to ponded water
- Has water absorption rate of less than 1 percent
- Is resistant to a wide range of chemicals, soils and microorganisms
- Corrosion resistant
- Excellent adhesion to concrete
- Can be applied to ‘green concrete’
- Fully adheres to wet surfaces
- Has self-healing and self-sealing properties
- Withstands thermal cycling
Typical uses in above-grade and below-grade applications are:
- Mud mats
- Below-grade foundations
- Pond and/or fountain liners
- Sea walls
- Elevator pits
- Plaza decks
- Garden applications
- Terraces, balconies
- Planters
- Vapor barriers
- Above-grade walls
The liquid rubber membranes have also been successfully applied in industrial tanks and containment tanks. System warranties are available that range from 10 to 25 years.
Roof Restoration Applications
Eventually, the liquid rubber membranes will challenge conventional rolled and sheet membranes for market share of new and remedial roof applications. At this time, the systems are being used as roof restoration and repair products. The primary advantage is that the membrane has excellent adhesion capabilities on all commercial low-slope and steep-slope roof materials. In addition to the benefits of a monolithic, seamless membrane, liquid rubber membranes possess the most important characteristics of a roof restoration membrane:
- It is a fully functional membrane and waterproof within seconds of application
- Dry mil thickness can range from 20 mils to 200 mils
- Can extend existing material’s service life 10 to 20 years
- Superior elongation and recovery
- Excellent adhesion to all roof membranes and metal
- Fully adheres to wet surfaces
- Has self-healing and self-sealing properties
- Withstands thermal cycling
- Can provide reflectivity
- Has Class ‘A’ fire rating
Typical roof restoration applications:
- Built-up roof systems (asphalt and coal-tar)
- Thermoplastics
- EPDM
- Sprayed foam
- Metal
- Tile
The liquid rubber membranes are excellent for repairs of flashings and penetrations. The spray equipment is small and mobile and most repairs can be completed with minimal manpower.
How to Apply Liquid Rubber Membranes: Below-Grade Waterproofing
The application of below-grade waterproofing is completed in a three-part process that utilizes liquid rubber membrane, water shield and a dimpled membrane drainage system.
The liquid rubber membrane system can be used on various substrates such as concrete, wood, and foam (ICF) to stop the infiltration of water into the structure. The system in normally used in below grade applications. It can be used in new construction, as well as on existing structures. The system is suitable for exterior and interior applications in all kinds of climates. The system may be enhanced by installing a water shield product between the rubber membrane and the dimple membrane, thus creating a waterproofing system that is virtually impenetrable.
Preparation of the surface is extremely critical and must be completed in compliance with the manufacturers requirements. All surfaces should be free from any loose material, oils, greases or other foreign material. Diesel fuel and mineral spirits should be removed from the surface. These should be removed prior to application by means recommended by the manufacturer. Power washing is oftentimes required.
All cracks, penetrations, existing seams, transitions, and corners should be addressed by incorporating polyester fabric with the liquid rubber in brush, roller or trowel grades.
The ambient outside temperature for application should range from 20 F to 100 F. Consult the manufacturer for required provisions in both extreme heat and extreme cold conditions. In colder conditions, make certain that the material is stored in a warm climate prior to use. Do not allow the material to freeze. The material should be thoroughly mixed prior to application.
Once the preparation and proper repairs have been completed, the liquid rubber membrane can be applied. Application can be completed with brush, roller or trowel in smaller application areas. Spray grade material shall be applied using specialized equipment. Apply material in a full and even application.
Install in strict accordance with manufacturer’s recommendations and approved submittals. Stir materials during application in accordance with manufacturer’s instructions to avoid product separation. Spray fluid component as a continuous, monolithic and seamless membrane of uniform thickness, beginning at the lowest point and terminating at the highest point. In the event the membrane is applied too thin, contact the manufacturer for recoat guidelines. Prior to application, create a grid across the roof with spray paint, allocating one drum of material per section of the grid. Perform cut-outs to check mil thickness and retain samples. Three test cuts are to be taken per 1,000 square-feet. In addition, continuously check wet millage by using the “T” post on a caliper mil gauge. After the liquid rubber membrane has cured, apply trowel adhesive to any visible voids. Comply with manufacturer’s recommendations for proper membrane terminations.
Apply primer over prepared and repaired membrane, doing so in compliance with manufacturer’s requirements. For vertical applications, apply the two-part liquid rubber membrane in a single, monolithic coat to minimum 85 mils wet/60 mil dry. Repair damaged installation in accordance with manufacturer’s requirements.
An optional application of water shield can be applied over the liquid rubber membrane to provide added waterproofing protection. The water shield also provides puncture resistance, added chemical resistance and extends life expectancy. These seam tape applications are typically required for long-term warranties. After allowing the rubber membrane to cure for a minimum of 24 hours, apply the water shield. Install seam tape on all seams, perimeter, and around all penetrations. If water shield is not being used, proceed to installation of dimpled membrane.
The dimpled membrane drainage system is typically mechanically fastened in a user-friendly application method over the completed rubber membrane system. These materials are prefabricated and are available in various heights and lengths to suit the application. After allowing the membrane to cure for 24 hours, install the dimpled membrane using dimpled membrane fasteners and membrane caps. Be sure to follow the recommended fastener pattern for the appropriate substrate. Backfill may take place immediately after the membrane application is complete. During the backfill, be sure to take precautions not to damage the waterproofing system.
How to Apply Liquid Rubber Membranes: Waterproofing
The liquid rubber membrane system is perfectly suited as a fluid-applied waterproofing system. The material’s excellent adhesion capabilities, high elongation properties and low water absorption rate are perfectly suited for all types of vertical and horizontal waterproofing applications. The system is ideal for plaza decks, balconies and terraces, planter boxes and all other waterproofing locations. Liquid rubber membrane can be applied as a waterproofing system with all types of surfacing requirements: coatings, living plants and green assemblies, pavers, and poured concrete.
The liquid rubber membrane system can be used on various substrates such as concrete, wood, and foam (ICF) to stop the infiltration of water into the structure. The system is normally used in below grade applications. It can be used in new construction, as well as on existing structures. The system is suitable for exterior and interior applications in all kinds of climates. The system may be enhanced by installing a water shield product between the rubber membrane and the dimple membrane, thus creating a waterproofing system that is virtually impenetrable.
Preparation of the surface is extremely critical and must be completed in compliance with the manufacturers requirements. All surfaces should be free from any loose material, oils, greases or other foreign material. Diesel fuel and mineral spirits should be removed from the surface. These should be removed prior to application by means recommended by the manufacturer. Power washing is oftentimes required.
All cracks, penetrations, existing seams, transitions, and corners should be addressed by incorporating polyester fabric with the liquid rubber in brush, roller or trowel grades.
The ambient outside temperature for application should range from 20 F to 100 F. Consult the manufacturer for required provisions in both extreme heat and extreme cold conditions. In colder conditions, make certain that the material is stored in a warm climate prior to use. Do not allow the material to freeze. The material should be thoroughly mixed prior to application.
Once the preparation and proper repairs have been completed, the liquid rubber membrane can be applied. Application can be completed with brush, roller or trowel in smaller application areas. Spray grade material shall be applied using specialized equipment. Apply material in a full and even application.
Install in strict accordance with manufacturer’s recommendations and approved submittals. Stir materials during application in accordance with manufacturer’s instructions to avoid product separation. Spray fluid component as a continuous, monolithic and seamless membrane of uniform thickness, beginning at the lowest point and terminating at the highest point. In the event the membrane is applied too thin, contact the manufacturer for recoat guidelines. Prior to application, create a grid across the roof with spray paint, allocating one drum of material per section of the grid. Perform cut-outs to check mil thickness and retain samples. Three test cuts are to be taken per 1000 square-feet. In addition, continuously check wet millage by using the “T” post on a caliper mil gauge. After the liquid rubber membrane has cured, apply trowel adhesive to any visible voids. Comply with manufacturer’s recommendations for proper membrane terminations.
Apply primer over prepared and repaired membrane, doing so in compliance with manufacturer’s requirements. For horizontal applications, apply the two-part liquid rubber membrane in a single, monolithic coat to minimum 85 mils wet/60 mil dry. Repair damaged installation in accordance with manufacturer’s requirements.
How to Apply Liquid Rubber Membranes: Roof Restoration
The liquid rubber membrane system was designed to significantly extend the service life of the existing roof system. Application can be completed over all conventional roof membrane systems, including BUR, thermoplastic, modified bitumen, EPDM, sprayed foam and metal (steep-slope or low-slope). When it is applied by knowledgeable installers, the system is an excellent economical choice for building owners.
The initial step in the restoration process is the proper repair of the existing roof system and preparation of the surfaces. All surfaces should be free from any loose material, oils, greases or foreign material. These should be removed prior to application by means recommended by the manufacturer. The liquid rubber membrane can be applied over damp surfaces; however, extensive ponding water should be removed prior to application.
Proper roof repairs should be completed in compliance with roofing industry standards. The one-part emulsion can be used for repairs to the existing membrane. Reinforcements should be added as required. All cracks, penetrations, existing seams, corners should be addressed using polyester fabric with roller/brush or trowel grade.
Once proper repairs and preparation is completed, the liquid applied membrane can be applied to the existing roof surface. The only exception is on aggregate surfaced built-up roof systems, which require additional preparation. Removal of all loose aggregate is required. On asphalt based BUR, the liquid applied membrane can be applied directly over the prepared surface. For coal-tar based BUR, a manufacturer-approved reinforcement should be set in a 3.5 mil wet profile of one-part liquid rubber. The reinforcement shall be set in a full and even application so that it is fully adhered with no wrinkles, buckles or blisters. The liquid rubber membrane is then set over the reinforcement. The reinforcement is required with coal-tar based BUR systems due to the continual flow of the coal-tar bitumen.
The application of moisture relief vents is also required on BUR systems to prevent gassing of bitumen contributing to blisters. Typical applications require one vent for every 1,000 square-feet. Additional vents may be used in areas with existing moisture in the system.
Once the preparation and proper repairs have been completed, the liquid rubber membrane can be applied. Application can be completed with brush, roller or trowel in smaller application areas. Spray grade material shall be applied using specialized equipment. Apply material in a full and even application.
Install in strict accordance with manufacturer’s recommendations and approved submittals. Stir materials during application in accordance with manufacturer’s instructions to avoid product separation. Spray fluid component as a continuous, monolithic and seamless membrane of uniform thickness, beginning at the lowest point and terminating at the highest point. In the event the membrane is applied too thin, contact the manufacturer for recoat guidelines. Prior to application, create a grid across the roof with spray paint, allocating one drum of material per section of the grid. Perform cut-outs to check mil thickness and retain samples. Three test cuts are to be taken per 1000 square-feet. In addition, continuously check wet millage by using the “T” post on a caliper mil gauge. After the liquid rubber membrane has cured, apply trowel adhesive to any visible voids. Comply with manufacturer’s recommendations for proper membrane terminations.
Apply primer over prepared and repaired membrane, doing so in compliance with manufacturer’s requirements. For horizontal applications, apply the two-part liquid rubber membrane in a single, monolithic coat to minimum 85 mils wet/60 mil dry. Repair damaged installation in accordance with manufacturer’s requirements.
The completed liquid applied membrane does not require additional surfacing for UV protection. Surfacings can be applied for esthetics or additional reflectivity. All surfacing material, such as coatings, granules, pavers or living applications can be applied.
All of the application methods and uses for liquid applied membranes are eligible for warranties from 10 to 25 years. Contact the manufacturer for warranty requirements.
