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Choosing The Right Coating For A Commercial Flat Roof



Selecting the Right Coating to Optimize Flat Roofing Performance and Lifespan


When someone utters the expression ‘a roof over your head’, the immediate inference is that they are talking about having a place to live; moreover, the first image that usually comes to mind is the shape of a peak, perhaps with a vertical chimney stack protruding from one of the two sloping sides.


Yet all buildings are not private residences and all roofing does not have a pitch or slope in its design. For commercial properties such as shopping centres, condominiums, office complexes, and multi-level parking structures, flat roofing is a preferred choice due to its wide range of advantages, including:

  • Flat roof installation is less labour-intensive (lower cost)

  • Longer lifecycle – better long-term return on investment

  • Ease-of-access for inspections and maintenance purposes

  • Toughness – lower overall costs of maintenance and repair

  • Provides more usable floor area for parking, green roofs, etc.

  • Offers more functional space e.g. for heating/cooling equipment

  • Improves energy efficiency (less open area under roof to heat/cool)

However, to optimize these benefits and possibly extend the lifespan of their investment, commercial property owners/managers must take appropriate actions to safeguard their flat roof from unnecessary repair work; one such measure would be to apply a protective coating to the roofing surface.


In the same vein that there are different types of interior and exterior paints for specific purposes and appearances, flat roof coatings are available in various types of material. Several options are offered in order to ensure that property owners/managers can match the coating to the particular composition of their flat roofing; the most common flat roof coatings (listed in alphabetical order) and their corresponding uses include the following:

  • Acrylic

  • Can be applied over existing bituminous or non-bituminous roofing

  • Provide a highly-reflective surface – can improve energy efficiency


  • Foam

  • Used on built-up roofing (BUR) systems or single-ply roof systems

  • Noted for its energy efficiency, longer lifespan, and cost-efficiency


  • Silicone

  • Often used to cover/protect spray polyurethane foam (SPF) roofing

  • Suitable in high exposures to UV rays, extreme temperature swings


  • Urethane

  • Largely installed on concrete (i.e. parking decks) or wooden surfaces

  • Typically not applied on other types of flat roof materials/membranes


  • Thermoplastic

  • Explicitly designed as an economical coating for metal roof systems

  • Also used on concrete, foam, modified bitumen, and single-ply roofs

  • Provides durable adhesion/bonding on roofs prone to ponding water


Clearly, there are several variables that must be taken into consideration with respect to coating a commercial flat roof; in addition to aligning the coating to the different types of roofing, other mitigating factors would be:

  • Structural soundness

  • Condition of roof surface

  • Seasonal weather conditions

  • Predisposition to ponding water

  • Exposure to chemicals, heat, UV rays

Consequently, to make an informed decision on the best coating option for their specific situation, it would be worthwhile for a property owner/manager to seek the advice of a contractor with considerable experience in commercial flat roof installation, coating, and repair; one such contractor is Dardanoi Group, one of the leaders in Ottawa’s roofing industry for more than 15 years.