Gustafsson Distributing, LLC

Est. 1948

"The Waterproof Coating Experts sm

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Post Example


Post set through plywood deck before being coated. This post was pressure treated, so it needed to be sanded at all areas to be coated to be sure that all preserving materials and other surface material was removed.


Post after being sanded, caulked, taped, base coated and texture coated. Although this post should remain watertight for many years, this type of installation usually has a counterflashing that extends vertically down over the texture coat at least 2 inches to insure that no water ever enters through the post itself and behind the waterproof coating. This counterflashing is normally the responsibility of the person in charge of the overall project whether that be a general contractor or a homeowner.

See below for a detailed instruction on how to seal around a post:


There are several ways that you can seal around a wood post. First is to use the deck coating material and tape to make an integral flashing. First cut a tight hole through the plywood and insert the post. Securely attach the post to the framing below the deck according to engineered details and or building code. Make sure the post and plywood are clean, dry, with no foreign material. If pressure treated post make sure you remove all surface salts to expose clean wood approx. 4 inches up from the deck. Install a cove of urethane sealant approx. 1/4 inch in both directions at the joint between the post and the plywood on all 4 sides of the post. Allow to cure overnight. Apply 1 " masking tape horizontally around the post leaving approx. 4 inches exposed at the base of the post. Apply a detail coat of deck coating to the post from the masking tape down and out onto the plywood about 4 inches in all 4 directions. (Do not coat directly onto the masking tape. Hold the coating just below the masking tape. Apply only the final coat onto the masking tape and remove the tape for a clean finish line.) After applying the detail coat to the post base and plywood, embed a piece of fabric reinforcing tape into the detail coat, centering the tape over the joint between the post and plywood. Since the tape is 4 inches wide, this means you would have 2 inches up the post and 2 inches out onto the plywood. Do this on all 4 sides of the post. Use a brush to work the tape into the wet detail coat to make sure there are no bridges, bubbles or wrinkles. Let the detail coat dry for about an hour until firm. Then brush apply a 2nd and 3rd coat over the tape allowing to dray in between coats. After this is completed and taping and detail coats on all other areas of deck are completed, you can proceed with the 1st basecoat and the rest of the deck coating, running each coat up the post to just below the masking tape. Run the final coat onto the masking tape and remove masking tape.

The second method would be to install a sheet metal "L" flashing around the post with 2 inches of metal onto the deck and metal 3 inches up the post. Cut the bottom flange of the metal so that the metal wraps around the post with one over lapped seam where the end of the metal covers the beginning. Nail securely. Apply the detail coat and fabric tape over the seam between the bottom metal flange and the plywood and continue per above. Caulk the top of the metal with urethane caulk to obtain a watertight seal. If you use this method it is best to counter flash or overlap the top of the metal with some type of cladding like a cedar wrap.




Example of a "split" 4X4 post at edge of deck.


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