Waterproofing a Roof Deck Takes Expertise

When it comes to waterproofing a roof deck, deck expert, Bill Leys recently shared his simple philosophy: “You can hire a contractor who is well-versed in deck waterproofing, or you can assume all the risk of choosing a system, figuring out the details, and installing it yourself.”

For someone like Mr. Leys whose company specializes in repairing and waterproofing failed roof decks and balconies, this philosophy becomes excellent free advice to home owners who need a deck built or renovated; but even more so to contractors who are not familiar with the intricacies of deck waterproofing.

Bill, along with most deck waterproofing specialists, sees the results of damaging water intrusion on a regular basis. What some people might consider an ‘add-on’ feature of the home; deck waterproofing is actually a critical factor to protect the entire home. Once water has infiltrated the building envelope and dry rot has developed, damage to the framing, shear walls, deck and possible living space below can turn what might have been a simple repair under $5,000 into a massive project upward of $100,000.

deck with wood rot
Inadequate details at perimeter and post were
likely responsible for allowing moisture to
invade and rot this deck.

While inadequate deck waterproofing keeps companies like Bill’s busy with repair projects, long-lasting waterproofing on a deck over living space is easily achievable and straightforward when best practises are followed and the most reliable products are used. There are a variety of ICC-ES listed manufacturers of Class A walking deck systems to choose from, so when you are making your building product selection this is an excellent resource. However a word to the wise, not all products in the same categories are tested to the same standards and you should be thorough when reviewing and comparing products.

For example, Duradek vinyl membranes are only one of over 20 Pedestrian Traffic Coatings listed with ICC-ES, but from this ICC-ES Comparison Chart* you can see that not all varieties were tested to the same standards. If you are selecting a membrane for waterproofing over living space, it is an important indicator of the product’s suitability for that purpose to see exactly what ICC approved uses the product is designated with.

waterproofed deck by Duradek
A deck waterproofed with Duradek vinyl membranes get
installed by trained professionals who know the details.

In an excellent article, “Building Waterproof Roof Decks” featured in Professional Deck Builder magazine, Bill Leys discusses some of these issues and more, and he indicates several areas of consideration to ensure decks are not vulnerable to water intrusion.

Bill highlights many factors that must be considered for successful deck waterproofing, the first of which is design. It is important to know what you need from your deck before beginning the framing.

Does it need to support a hot tub or other heavy weight items like oversized ceramic planters or outdoor kitchen assemblies?
Is the deck to be over living space or cantilevered out on joists?
What kind of water routing and slope will be required?

It would be a costly and frustrating experience to find out your deck is sloped inadequately for your waterproof membrane once the membrane has been installed.

This is where working with a professional, experienced deck builder can save you a ton of time and money right from the start. If you contractor uncle says he will build you a deck when the family comes for a visit, are you confident that he knows that the deck should never be level with the floor of the interior, and should actually be at least 1 ½ inches below the level of the interior floor; or that he knows the proper spacing of joists and fasteners to support the load of your expected capacity?

wood rot at door sill
Door sills can be a target for moisture invasion if small but critical details are missed.

While many do-it-yourselfers will shrug off concerns about building code, when it comes to deck building and waterproofing the risk of not using a professional can be an exponentially more expensive route than paying a little more to have it done right from the start.

If you’d like to talk to a deck waterproofing specialist, contact a Duradek installer in your area to discuss your deck waterproofing and maintenance needs.

* Information obtained from ICC-ES website, researched and compiled by Duradek.

bill-leysBill Leys owns Deckexpert.com and Central Coast Waterproofing in Arroyo Grande, California. Bill is a regular presenter at building industry events to share his vast knowledge on deck waterproofing.

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