Dry Deck Construction

Introduction: A common problem that many homeowners have with second level decks is how to effectively create a dry deck or deck waterproof so that they can gain a dry area underneath the deck, either for storage or a walkout patio. There are several alternatives for a dry under deck that can be considered and some are DIY tasks that do not require professional help.

A under deck waterproofing system is a novel way of waterproofing a deck and retaining the existing natural wood surface on top. This requires a ceiling to be installed underneath the deck, attached to the joists. The sealing is constructed of metal roofing material installed in such a way that the water that comes through the deck surface drains away into a gutter situated at the edge of the ceiling. This is the same metal roofing that is used on roofs in place of shingles. I installed this system approximately fifteen years ago while living in the mid west. It was an idea that I adopted after putting metal roofing on a shed. It is a very practical solution to provide a dry area underneath the deck.

There are other methods for a dry deck such as installing a vinyl membrane over the existing surface. The membrane system is a roll out vinyl sheeting which may typically have a core of a heavy duty polyester fabric to provide protection against puncture and tearing. With this method you cannot retain the original natural wood appearance of the deck.

Another method is to install aluminum decking instead of wood planking. Normally this type of decking would replace the original wood planks on your deck. Channels on the underside of the decking permits water to drain away to the edge of the deck. The drawback is it is very expensive can get very hot underfoot in mid-summer.

There is also a vinyl ceiling that attaches to the underneath of an existing deck. The system is made of interlocking parts that are easy to cut and install. The vinyl system gives your ceiling a corrugated look. Water and other liquids from the upper deck are diverted into gutters and to be drained way. Seamless gutters and downspouts can be used to quickly direct liquids away from your home.

Whether you are looking for a ceiling for your lower level deck or if you want to create a dry place for storage or a walk out patio from the lower level, a waterproofing systems will help you reclaim the space under your deck. Installing metal roofing is the least expensive and can be performed by a DIY home owner.

Installing a Dry Deck System :


For most DIY home owners installing metal roofing under a second story deck is not a difficult task. The medal roofing material can be ordered in any size and in many different colors. It is simply screwed in place from underneath with special water tight self tapping screws. To insure that you get the drainage from the ceiling it must be sloped properly. This can be accomplished by installing ceiling strapping. See Fig. 1 and 2.

A piece of strapping should be nailed in place at 12 inch intervals and with an increase in thickness by 1/4 on each strip. If your deck is twelve feet wide this will provide you with a 3 inch slope which is sufficient to drain the water away as nearly as fast as it accumulates. I recommend that you install a gutter drain at the end of the ceiling to drain the water away from the deck.

Although there are a number of other methods to create a dry under deck, this method is much cheaper that the alternatives and is very effective and looks great. See Fig. 3 for a completed than metal ceiling under a second story deck.

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