Under Deck Waterproofing Systems
Many deck owners want to create usable space below their deck. Whether this space is used for entertaining or storage, under deck waterproofing systems are being installed on many projects. There are several systems that are currently on the market. Dry Snap, Rain Escape, and Dry Space are a few after market options.
Dry Snap is ideal for existing decks that need to be waterproofed. This product is installed below the existing deck framing. The biggest disadvantage of Dry Snap is that the waterproofing system acts as both the water protector and the finished ceiling as well. This makes it difficult to add lights or ceiling fans to the area below. Dry Snap states on their website that installing fans and lights is possible, but after attempting on various projects, we've found this to be nearly impossible.
Both Rain Escape and Dry space system are a better option if you are adding the water proofing system at the same time as deck construction. These product have to be installed during the construction of deck prior to installing the decking boards. Both systems include plastic joist bays directing water flow away from the house to a gutter located at the perimeter of the deck. The disadvantage is that you have to later cover the system with a separate ceiling cover adding addition cost.
Our preferred method is to custom build water trophs using EPDM rubber membrane. EPDM is a rubberized roofing system used in flat roof applications and can also be used for waterproofing decks as well. A sheet of rubber drapes over the joist bays directing water to the gutter similar to the Rain Escape system. The advantage to the EPDM system is the cost is less and the rubber sheets are easier to work with making custom decks(non-square) much easier to waterproof.
To learn more see our video on how to water proof a deck:
I cannot stress the importance of properly installed flashing for any deck or screen porch project. The severe weather of the Washington Metropolitan area will destroy any unprotected wood. If your deck is not flashed properly you are putting yourself and your family in harm’s way. Last year I did over 200 deck estimates. The majority of these estimates included either the demolition and removal of an existing deck or an addition to an existing deck. More than 50% of the decks I visited were not flashed and open to rain and snow damage. It’s a crime that a contractor would not take thirty minutes and install flashing properly. The material does not cost very much and the installation is quite simple.
Second, the flashing must go behind the siding. You want the flashing to be approx. 6” above(behind the siding & ledger) your ledger board. Once the first piece of flashing is installed you can attached the pressure treated ledger board sandwiching the flashing to the house. The final step is to install a piece of ‘L’ flashing that sits on the ledger board and goes behind the siding. This piece keeps water from entering the house and flowing in front of the ledger. The first piece is for added protection.