Bessern Moisture Mitigation Coatings Construction Products

Fiberglass Roof and Walking Decks, Is There a Better Way to Waterproof?


Fiberglass is currently used to waterproof roofs and walking decks. While fiberglass has long been used for roofs and walking decks, it is not without serious drawbacks. Both the fiberglass and resins involved have significant detriments.


The issues with using fiberglass for waterproofing decks can be broken down into three main points: odor, dust, and cracks. While the odor and dust are relatively short-term problems, cracking will cause long-term damage to your deck and allow water intrusion into the occupied spaces below.


The polyester resins used to bond and waterproof the fiberglass are often strong smelling, especially the styrene monomer solvent. While this is not always an issue, there can be lingering fiberglass odors long after the completion of the deck.


Fiberglass is a powerful irritant to the skin and can be especially harmful to the eyes and lungs. Before the top coat is applied, the fiberglass must be sanded down to a proper finish. This sanding process creates a large amount of fiberglass dust which can cause discomfort, irritation, or more serious problems.


Cracking is a major concern with fiberglass decks. Every deck is built to account for some level of movement, but fiberglass is rigid once hardened and cannot withstand the movement of the underlying deck. This movement can lead to cracking and delamination in the fiberglass which compromises the waterproof resin layer. Once water gets through the fiberglass layer it can do lasting damage beneath the deck surface.


Urethane is an alternative way to waterproof balconies and pedestrian decks which does not come with the same drawbacks as fiberglass, yet has a similar price. This type of system uses a 2-4 step process with a proven track record dating back decades. The process uses urethane and urethane hybrids to seamlessly coat the deck and prevent roof or balcony leaks.


Urethane deck coatings have an abundance of benefits when compared to fiberglass. Unlike fiberglass, urethane is low-odor, has no irritating dust, and is resistant to stress cracks thanks to its flexible and impact-resistant properties. It is also fire rated, comes with a 5-year warranty, can be applied in below-freezing temperatures, and can even be applied to concrete decks.


During the application of the urethane coating, there will be a slight odor until the coating has fast cured. This process typically takes 6-12 hours. The odor will be similar to that which results from urethane coatings applied to wood floors indoors.


Urethane coatings for roof decks require no sanding. Sanding is the process that causes irritating airborne fiberglass and resin dust in fiberglass deck systems.


While deck cracks and delamination can occur in fiberglass coatings due to the movement of the deck, the same will not happen to urethane coatings. Even when cured, urethane is flexible enough to withstand the stress of deck movement. In a fiberglass deck, water will enter through stress cracks, freeze, and expand, thus damaging the structure.


Along with movement stress, impacts are a common cause of cracking in fiberglass coatings. Fiberglass is much more brittle than urethane and is prone to cracking upon impact. Urethane will more evenly spread the force of impact throughout its total surface area, reducing the risk of cracks.


Many urethane systems have been independently tested for fire resistance with Class A and B ratings for roof coverings.


Fiberglass deck coatings must be applied in temperatures above 50 degrees Fahrenheit. Urethane coatings can be applied in temperatures below 32 degrees Fahrenheit. This is useful because the urethane coating can be applied during the off-season when the deck is not in use.


Urethane is the perfect coating material for concrete decks. Concrete expands and contracts with the weather and, thanks to its flexibility, urethane can expand along with it. The urethane coating can even bridge the cracks that develop within the concrete over time. It is for these reasons that urethane is commonly used to coat other concrete structures such as parking garages, commercial buildings, and marine environments.


Urethane coatings come with a warranty. Warranty terms are based on the type of urethane coating system installed.


Waterproofing decks correctly for long-term success is an important step that should not be downplayed. There are many waterproofing and deck coating systems on the market. However, it is prudent to check the performance of the deck coating system you select for your project for both new construction or repair. While both fiberglass and urethane coatings cost about the same to apply, urethane coating systems have a significant number of advantages. Most notable are the lack of a lingering odor, the elimination of irritating dust, and the ability to resist cracking.

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