All factors that can possibly be integrated into the design, implementation and final outcome for a long term, high quality waterproofing system must be considered. Waterproofing system design must be carefully and thoughtfully selected and carefully specified, installation must be carefully choreographed and watched and be extremely well coordinated by a very competent team. The demise or failure of a waterproofing system on an underground parkade or occupied, below grade space could mean the demise of functionality for that area of the building.

A comprehensive listing of “Waterproofing System Design Criteria” should be established prior to waterproofing system selection. A specific custom designed waterproofing system is necessary – “it is better to design a waterproofing system than to pick one”.

Residential construction, wood framed buildings and other sensitive occupancy structures provide a number of challenging variables for waterproofing system design at their lower areas and also higher above ground. These variables include – but are not limited to:

  • The sensitive nature of the building
  • The significant, potential, negative impact of wind and storm events and exposure of the waterproofing system to significant water events
  • Significant difficulties in being able to inspect and repair the waterproofing system once in service 
  • The physical orientation of the waterproofing areas, i.e. some levels completely inaccessible – vertical waterproofing areas – other areas somewhat accessible such as plaza decks
  • The requirement for a very long service life waterproofing system with no or very minimal leakage
  • The sensitivity of the waterproofing system to the conditions of the site and the project – difficult access, difficult application, hydrostatic pressures and other constraining factors
  • Necessity of a redundant waterproofing membrane as possible
  • Drainage requirements – additional drains, drain type for replacement, plumbing issues, slope to drain issues and general water management
  • Proper and long term flashing details of penetrations, projections, piping, electrical wiring, conduits or accessories and all other deviations through the waterproofing system
  • Detailing of all pipes and projections through the waterproofing deck and waterproofing system
  • Insurance and code provisions – FM requirements and/or other specific requirements
  • Puncture resistance requirements
  • Lowtemperature flexibility, elongation, water immersion and movement tolerance
  • Fire resistance 
  • Effective and proper surfaces systems for the waterproofing system especially plaza decks with intensive vegetative designs
  • Energy efficient and environmentally responsible design
  • Adjacent wall systems and other abutting surfaces that must be watertight and must not compromise the waterproofing system or lead to leakage
  • Very low life cycle costs – initial costs are not the only value consideration

Additional Roof System and Specification Considerations

1. Adhesion And Moisture Tests and all other applicable test procedures to ensure that the substrate is compatible with the waterproofing system must be undertaken. All processes required for complete, long term adhesion of the waterproofing system should be should be made. All applicable factors including according to Factory Mutual standards – Factory Mutual standards are generally recognized to be the most stringent in the industry.

  1. Moisture Measurements and Site Conditions should be assessed. Waterproofing system type, amount of insulation as required and configuration and other waterproofing system factors must act in concert with the site and project conditions.
  1. Insurance Coverage – the requirements of all concerned insurance carriers must be addressed. Factory Mutual requirements, or others, as required, must be tabulated in written form and the waterproofing system must satisfy those requirements.
  1. Flashing Details must be constructed to resist all forces and conditions – slippage, delamination, tearing, weathering and provide long service life and protection of the waterproofing system. Full metal coverage – typically stainless steel and proper securement using stainless steel fasteners are required. 
  1. Waterproofing System Construction must be mechanic and project suitable. The waterproofing system must remain in place on the substrate and all design criteria must be satisfied before the specification is written. The waterproofing system must be suitable for the building areas for which it is intended.
  1. Waterproofing System Specifications must be all inclusive. Procedures and execution processes must be clearly spelled out. Materials must be compared to a standard and the manufacturer(s) and type and reference standards must be listed. 
  1. Facility Requirements, limitations, procedures and constraints must be clearly and prominently listed in the specification. The bidding contractors have to know where and how they can set-up, what safety training is required for the facility and all other unique requirements that will cost money. The specification is the document that provides information for all parties to be on the same page.
  1. Waterproofing System inspection must include all the relevant information relating to the installation of the waterproofing system. Ambient conditions, temperatures of materials at application, labeling of materials, verification of sizes and thicknesses, sequencing of materials, good installation practices, conformance with the specification, protection of the facility, proper application rates and techniques and many other very important factors must be noted. Photographic documentation of the project is also necessary – pictures are invaluable. Trouble shooting of specific details during the course of the project is a necessary component of detailed waterproofing system inspection.
  1. Quality Control and Resolution of Details – the waterproofing professional on the project must have the knowledge and decision making skills to address quality issues, difficult details and other situations that require resolution – merely having a “body” on the roof who must “call the office” for resolution is of little practical use – the professional on the site must be just that – experienced, knowledgeable and willing and able to make decisions and resolve issues.
  1. Contractor Responsibilities must be clearly delineated in all project documents. The contractor must provide the labour, materials and equipment necessary to complete the project successfully. The contractor must verify that all materials can be installed to accommodate building design, pertinent codes and regulations and the manufacturer’s current recommendations”. These considerations should already have been satisfied long before the contractor reaches the site.
  1. Manufacturers must be pre-screened for appropriate waterproofing system components of appropriate quality. All components must be compatible and the manufacturer must provide warranty coverage that means something. 


Roof System Options and Comparative Budget Information For Each Option


  1. Please see waterproofing system schematics following for the sequencing of the waterproofing system components.
  2. The drainage mat and insulation layer for all three budget systems have been kept constant – the cost and performance differences are related to the waterproofing system/membrane

GOOD – Waterproofing System One – 1 Ply Self-Adhered Waterproofing System 

Rubberized Asphalt or Polymeric Formulation – Non Reinforced

  • 1 ply of peel and stick rubberized or polymeric waterproofing membrane with primer (rubberized) or as required (polymeric)
  • All accessories and transition materials
  • 2 inch (minimum) extruded polystyrene insulation
  • Polymeric drainage mat or membrane
  • 26 gauge, prepainted sheet metal details

BETTER– Waterproofing System Two – Liquid Applied Waterproofing System – One or Two Component Urethane – Vertical or Horizontal

  • Two coat application of modified urethane, liquid membrane over primed substrate
  • All accessories and transition materials
  • 2 inch (minimum) extruded polystyrene insulation
  • Polymeric drainage mat or membrane
  • 26 gauge, prepainted sheet metal details

SUPERIOR – Waterproofing System Three – 1 Ply Thermally Fused Waterproofing  System With Reinforcement – Torch Or Hot Air Welded Or Self-Adhered

  • 1 ply of thermally fused (or peel and stick) rubberized, waterproofing membrane with primed substrate
  • All accessories and transition materials
  • 2 inch (minimum) extruded polystyrene insulation
  • Polymeric drainage mat or membrane
  • 26 gauge, prepainted sheet metal details

Comparison Chart For Three Waterproofing Systems – GOOD, BETTER, BEST

ComparatorSystem 1 – GOOD – 1 Ply Self-Adhered Membrane Sheet – Non-ReinforcedSystem 2 – BETTER – 
2 Coat Application of Modified Urethane, Liquid Applied  Waterproofing
System 3– BEST – 1 Ply, 
Thermally Fused, Or Self-Adhered – Reinforced Waterproofing Membrane
SubstrateCast or Pre-Cast Wall Cast or Pre-Cast WallCast or Pre-Cast Wall 
PrimerAsphalt based emulsion or polymer primerAsphalt based primerAsphalt based primer or polymer primer
Membrane MaterialNon-reinforced, rubberized membrane sheet or polymeric membrane sheet
Liquid applied, modified urethane membrane applied by brush or roller – vertical gradeReinforced, SBS rubberized membrane sheet – thermally fused – torch or hot air or self-adhered
Typical Material ManufacturerSopraseal 1100 or Blueskin – rubberized or 3M polymericTremco TG250 or Soprema AlsandSoprema Colphene 3000 self-adhered of Colphene Flam 180
Course of Insulation2 inch extruded polystyrene insulation – minimum or as project requirements dictate2 inch extruded polystyrene insulation – minimum or as project requirements dictate2 inch extruded polystyrene insulation – minimum or as project requirements dictate
Drainage Course1 layer of polymeric membrane or dimple mat1 layer of polymeric membrane or dimple mat1 layer of polymeric membrane or dimple mat
BackfillClear, granular fill or gravel – no clayClear, granular fill or gravel – no clayClear, granular fill or gravel – no clay
Breathable MembraneNONONO
Fully Adhered MembraneYESYESYES
Application Over Green ConcreteNONODEPENDS
Surface FinishPolymeric facer – smoothExposed urethane membrane – smoothBituminous surface – rubberized asphalt
Cold Temperature ApplicationBituminous – 0° C 3M Polymeric -10°CLow Temperature Limit +5°CLow Temperature Limit -15°C
Toughness Of Membrane
FAIR – unreinforced sheet can be puncturedGOOD – film strength of membrane is high and membrane is seamlessVERY GOOD – reinforced fully adhered membrane difficult to puncture
Resistance To LeakageFair – medium duty membrane resists leaks if completely intactGood – strong seamless membrane, fully adhered to substrateExcellent – the reinforced, fully adhered membrane prevent the passage of water
Ease Of Installation Excellent – the membrane is a peel and stick applicationGood – Care must be taken to maintain film thickness and ambient weather conditions are important – especially humidityExcellent – the membrane is fused to the foundation wall and the rubberized asphalt “wets” the concrete very well
Low Temperature Flexibility
Good – rubberized membrane flexible to 0° C – Polymeric flexible to – 15° C

Very Good – cured urethane membrane flexible down to -10° C
Excellent – rubberized membrane flexible down to – 20° C
Resistance to Thermal ShockGood – membrane is rubberizedGood – membrane is flexibleVery Good – membrane is rubberized and reinforced
Resistance To Frequent Exposure To WaterFair – membrane is rubberized but no reinforcementFair – extended exposure to moisture can allow penetration of moisture through pinholes in membraneVery Good – reinforced, rubberized membrane very resistant to water penetration
Longevity of MembraneGood – rubberized membrane is quite resistant to agingVery Good – urethane membrane is tough and weather resistantExcellent – membrane is rubberized and reinforced

The best assurance for a good roof system is “good design, good materials and good labour”.



Blindside waterproofing applications are best accomplished by either Bentonite Clay sheets or panels, reinforced, rubberized modified bitumen sheets or for difficult exposures, a combination of both approaches.

The Bentonite clay will expand with exposure to water to about 8 times its dry volume and forms a sticky, gelatinous substance that clings to surfaces and prevents the passage of water in the long term. Typically, Bentonite clay Is used in continuously wet situations, where the clay can stay wet.

The modified bitumen system is used in conditions where water exposure can be intermittent, although continuously wet conditions are compatible with the modified bitumen system. The advantage of the Bentonite Clay systems is the ability of the clay to close over and seal around projections, punctures and penetrations.

In severe situations with significant water and continuous wet conditions – a combination of Bentonite Clay and the modified bitumen systems will provide the best waterproofing protection. The modified bitumen membrane provides a stable, consistent membrane that provides the bulk of the waterproofing performance while the Bentonite Clay seals around imperfections and punctures and provides redundant waterproofing to additionally seal the interior of the building from hydrostatic forces on the exterior.



The two types of waterproofing systems that provide leak free performance in the long term for difficult applications such as plaza decks with intensive greenscaping and vegetation, planters that are continuously subject to water exposure under a vegetative loads and podium decks that are covered with commercial applications, extensive surface finishes and other very hard to remove systems over the waterproofing system.

The oldest and most proven system for waterproofing of horizontal applications is the reinforced, double pour of hot applied rubberized asphalt. The heavy bodied rubberized asphalt is heated in an oil jacketed kettle and applied in two pours by the “pour and squeegee” method. Hot rubberized asphalt is applied to the primed concrete substrate at the rate of about one pound per square foot – immediately after application, a limp polyester reinforcing membrane is embedded into the hot rubberized asphalt. A second pour of rubberized asphalt is applied at the same rate over the base pour and polyester fabric with the fabric texture being completely obliterated. 

If an extremely long life waterproofing system is desired for areas that essentially never be accessed – an second layer of polyester reinforcing fabric can be embedded into second pour of rubberized asphalt, and then a third pour of rubberized asphalt would be applied over that second layer of polyester to produce a highly elastic membrane that will resist water for 5 to 6 decades. The installation of two layer flexible membrane flashings at all critical areas completes this essentially permanent system.

Flashing membranes and other accessories are utilized to complete the waterproof application of this very substantial membrane – on the order of ¾ inch thick. Rubberized asphalt will function, in a well constructed system, for several decades (4 plus) without deterioration or leakage. Rubberized asphalt does not break down for a very long time.

The second proven long term waterproofing membrane for horizontal applications utilizes two plies or layers of polyester reinforced, rubberized ply sheets adhered in kettle grade rubberized asphalt. The kettle grade rubberized asphalt is not as heavy bodied as the waterproofing, rubberized asphalt which acts as the waterproofing membrane. The kettle grade rubberized asphalt acts as an adhesive for the factory fabricated, reinforced ply sheets which, when adhered to the primed concrete substrate in a solid mopping of the rubberized asphalt, produces an exceptional tough, moisture resistant 2 ply waterproofing membrane – each ply of the membrane is mopped with a solid application of rubberized asphalt. The resultant rubberized membrane is extremely flexible, puncture resistant that will elongate and recover essentially permanently. The service life of this type of rubberized membrane, in a well constructed system, is 50 years plus.

Other available systems include: liquid applied, single ply membranes, various sheet membranes and other proprietary systems and membranes that are simply not tested and proven – serious waterproofing projects require systems that are proven to perform and perform for the very long term. Untested or medium grade systems will prove to be very difficult, expensive choices for buried or extremely un-accessible waterproofing situations.