Aeratis offers two solutions for making projects watertight or waterproof.  Waterproof is defined as an application that will eliminate ANY water from passing into the sub-structure. A watertight application is when it is not mission critical that not a drop gets through to the substrate but you would like to eliminate as much water from passing under the porch as possible.

One feature that makes Aeratis products unique over all other competitors in the exterior living space category is their performance in both waterproof and watertight applications.

Overview of a Waterproof Installation (See Waterproof installation instructions for complete details) – The first step is to plan the spacing from top of the joist to the bottom of the door/threshold height.  The amount of space between the bottom of the door to the top of the joist will dictate the installation details.


On top of your joist, you want to install pressure treated plywood or Advantech. Fasten the plywood to the joist with staples, nails or screws. Make sure you use construction adhesive.  Side Note: Make sure your pressure treated plywood is KDAT or Kiln Dried After Treated.  Make sure your joist are spaced16” OC.  On top of the plywood, you will install the peal and stick membrane. If possible run the membrane up the wall at least one foot and make sure you completely cover the rim joist on the outside. This is your waterproofing insurance. Little to no water should ever get to this membrane but in case it does, make sure this is installed perfectly with the proper overlap (50% overlap).

On top of the membrane you have several options; The best case scenario, you add sleepers 16” OC running parallel to the structure (opposite way the water will flow). On the bottom of the sleepers, you have to cut our channels so that it does not dam up any water if water gets to the membrane.  You can do this with a router bit or even a dado bit on a miter saw. Do not cut more than 1Ž2” deep.

On top of your notched sleepers, it is best practice to use a construction adhesive and then fasten the porch boards down with stainless steel nails or staples with a pneumatic flooring nailer.

No Room for Sleepers

If you do not have room: If you do not have room to add the sleepers, you can fasten Aeratis directly to the membrane. You MUST use 3 inch trim head screws and fastener the Aeratis boards through the membrane, through the plywood and hit a joist with each screw (16”OC). Plywood is not an acceptable substrate to fasten your Aeratis boards to. You must hit a joist, brace or sleeper with your fasteners. If you do to have sleepers, having the perfect slope becomes more critical. Never allow the slope to be less than 1Ž4” per foot of depth.

Critical Elements

Slope – Slope is critical when creating a waterproof or watertight project. The slope should be no less than 1Ž4” per foot. So if your project is 10 feet deep and 40 feet long you should never slop the framing any less than 1-1/2”.  Many building municipalities require a 2% slope on all exterior living space.  SIDE NOTE: You may consider this to be excessive until you consider that it is not out of the ordinary for a joist to crown 1/8” of an inch as the pressure treated material dries out.  The key is to provide enough pitch to have the water moving continuously away from the structure.

Board Directions — The direction the boards are installed really makes a huge difference. Keep in mind; always install the boards running the direction you would like the water to flow.  If you run the boards the opposite direction, the flow of the water is slowed down.  In a waterproof or watertight installation, never install the flooring boards parallel to the structure with butt joints.

Membrane – The key difference between a watertight and waterproof installation is the use of a membrane.  Never use an EPDM membrane. Select a membrane like Grace Ice and Watershield that will gasket fasteners. With a membrane like EPDM, you cannot penetrate it with fasteners. Also note, it is not advised to try to float a frame or sleeper system on top of your membrane. Over time, you wood will begin to warp and this will become obvious because the floating system will not be nailed down.

Quarter Round – Make sure you seal up where the boards meet the house wall with a healthy bead of silicone and our quarter round. This will stop the water from sliding down the wall and behind your porch flooring boards.

See Complete installation instructions Link