Deck waterproofing process

Preparation

Our deck waterproofing process needs a good solid CDX exterior grade plywood surface with a minimum thickness of 5/8 inch (3/4 inch preferred) with a maximum joist span of 16 inches.  The first step is to remove the old surface coatings and inspect the plywood substrate for any dry rot, soft or spongy areas, cracks or joint separations and any potential areas of water leakage or damage.  If any of these conditions are found, removal of the plywood substrate may be required to inspect and repair the supporting joist system.  Flashing may also have to be replaced if it does not meet our standards.

Metal Lath

When the plywood substrate is in good condition or new plywood has been installed, all of the joints and seams are taped and covered with an epoxy sealer.  If new flashing is being installed, it is installed around all of the edges, along all adjoining walls and anything that protrudes through the surface.  A reinforced galvanized metal lath is stapled (20 - 24 staples per square foot) to the plywood substrate with all seams in the lath overlapped at least 2 inches.  

Base Coat

The base coat is cement mixed with a cement modifier and water.  It is applied by pouring it on to the surface and spread out with a trowel.  The base coat is smoothed to the top of the lath making sure it covers the flashing and gets into the corners.  As soon as the base coat is dry, usually 1 to 2 hours, any high spots or ridges are scraped smooth.

Slurry Coat

A slurry coat is cement mixed with a cement modifier, resins and water.  It is applied over the base coat to smooth out the surface and to provide a good bonding surface for the fiberglass layer.  When the slurry coat is dry the surface is scraped to remove any bumps or ridges so we have a smooth surface.

Fiberglass lath

The fiberglass lath is added to give maximum reinforcement to the surface.  A slurry mix, with waterproofing resins added, is applied on the fiberglass to saturate through and laminate it to the surface below.  When the surface is dry any bumps or ridges are scraped off.

Texture Coat

At this point any number of surface finishes can be applied.  Typically we apply a knocked down texture which is sprayed on and then knocked down with a trowel.  Optionally you can elect to have a different finish applied.  There may be a colored slurry grout coat applied, a taped pattern for flagstone or tile and a colored mix that uses the skip trowel method to apply the texture.  When the surface is dry, color accents are applied to make the surface look like real tile or stone.

Color Topcoat

On a typical deck with knocked down or orange peal texture finish, an acrylic color topcoat sealer is applied to the surface.  For other finishes there may be other coloring options and the surface is sealed with a clear sealer.