Design Tips for Low Clearance, Low Ventilation Decks
This is the harshest environmental condition you can subject a deck board to. however, if you take the necessary steps, you can help manage and minimize the damaging effects of moisture on deck boards.
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Use narrower and thicker decking boards. 5/4 x 4 nominal decking is ideal, 21 mm x 4 is the next best option
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Face screwing the deck boards is the strongest fastening method and will help minimize cupping.
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Hidden fasteners are not recommended for low clearance, low ventilation decks
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On rooftop and patio top decks, the Eurotec Deck System does not impede the flow of water for under-deck drainage. This system works great for decks with heights between 4” and 20” from the top of the roof to the top of the decking
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For decks with less than 4” clearance (top of roof to top of decking boards), sleepers are often specified.
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Article on installing decking with sleepers here. The joists must run parallel to the direction of water flow, towards the drains.
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Adequate drainage is imperative.
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Adequate ventilation is critical.
Installation Tips for Low Clearance, Low Ventilation Decks:
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The only space the deck will be venting is between the deck boards
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That’s one reason why narrower, thicker deck boards will perform better (5/4 x 4 or 21mm x 4 nominal decking)
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Another reason is narrower deck boards expand and contract less
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Thicker deck boards perform better and are less prone to cupping
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Face screws will help minimize deck board movement, especially cupping.
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Spacing the deck boards (after acclimation) to 3/16”, will allow for best ventilation.
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Pre-finishing the deck boards, on all 4 sides, prior to installation, helps protect the deck boards, especially initially, even if your goal is to allow the boards to turn silvery gray.
We hope you enjoyed this article. Please visit MataverdeDecking.com for additional information about wood decking species, decking galleries, decking samples, decking installation guidelines, “How Woods Weather Guidebook” and more.
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