Interstitial Spaces Posing Waterproofing Complexities in Recreational Decks

Pool Deck Miracote

Picture this: Just after the construction of a sleek, gorgeous rooftop space of a luxury condominium, the building manager reports major leaks into the building’s top floor. By ill luck, that floor houses the multi-million dollar penthouse units that are scheduled for turnover next month.

The scenario above is probably the worst nightmare for an architect or design professional. After all, project designs and material specifications should anticipate waterproofing issues in any roof deck. Recreational decks, however, carry waterproofing complexities that may exceed design challenges that architects typically encounter when working in conventional roofing construction.

Sometimes, Beauty Comes at a Price

Stunning rooftop amenities have become selling points of luxurious hotels, condominiums, and commercial buildings, especially in areas where real estate markets are very competitive. These recreational decks are often part of new construction, but they’ve become the go-to projects of roof renovations, as well. Sometimes, the beauty of these amenities comes at a price.

Rooftop amenities, such as sun decks or swimming pools, often require constructing an elevated surface for walking above the structural roof deck and waterproofing assembly. (The waterproofing assembly may include cementitious waterproofing and waterproofing membrane.)

Structural elements, such as stem walls, support the raised deck. These walls divide the interstitial space into different roof zones, which pose several drainage and waterproofing complexities.

The Case of Interstitial Spaces

On a conventional roof, the surface is clear and undivided. The square footage of a particular roof area determines the size and quantity of roof drain needed. This also makes the waterproofing design simple.

On the other hand, the drainage design for interstitial roof zones should be developed with the layout of the stem walls in mind. It usually requires building dedicated internal drains for each zone, which may be impractical for many project teams.

The stem wall and waterproofing design must also consider alternative paths for water flow between zones. Placing “block-outs” at the base of stem walls is an excellent way to designate those paths, but only if the waterproofing design includes applying the membrane continuously below the stem walls.

Also, architects need to consider possible waterproofing repairs in interstitial spaces. These spaces provide designers with a convenient location to discreetly install utilities that service rooftop amenities. Utilities may include piping for water taps and landscaping irrigation and electrical conduit for light fixtures.

Some contractors, however, route the utilities haphazardly to ensure they are out of sight in the deck. They don’t match the design of the route with the waterproofing design in the interstitial spaces. As such, waterproofing issues become impossible to repair without relocating or removing the utility lines.

Coordination among architects, design professionals, and contractors is vital in amenity roof projects. The drainage and waterproofing materials, design strategy, and application should go hand in hand with the construction of interstitial spaces needed for recreational decks. This coordination will also benefit the entire team when correcting water leakage issues in the future, like in the scenario above.

If you want to learn more about waterproofing recreational decks, Miracote is here to help. Contact us today.

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