EIFS Liquid Moisture Barrier

EIFS Liquid  Moisture Barrier

An in depth look at EIFS Liquid Moisture Barrier

Traditionally, the substrate (OSB) was wrapped with a cloth type building wrap, but after some pretty extensive testing done by The Oak Ridge National Laboratory (ORNL) it was proven that a EIFS liquid moisture barrier is much more effective in an EIFS application for moisture drainage. A liquid moisture barrier can be used on a lot of substrates but we are going to focus on OSB and fiberglass board, which are two common EIFS approved substrates. For this explanation of EIFS liquid barrier we will be describing the process using Dryvit™ products. When applying a Backstop NT™ (Dryvit’s™ liquid moisture barrier) over OSB and Fiberglass Board the first step is to put EIFS moisture barrier tape (Grid Tape) over the joints, and applying Backstop NT™ Texture over the Grid Tape. The next step is different for OSB and Fiberglass Board. For an OSB application after the Backstop on the joints is dry another coat of Backstop is applied. This time Backstop NT™ smooth is used and is applied over the entire substrate including over the joints. After that coat is completely dry another coat is applied. The reason for the two coats of smooth over the OSB is that the wood absorbs a lot of the material. In a Fiberglass board application Backstop NT™ Texture is applied over the entire substrate including over the joints. When applying the liquid moisture barrier it is always done with a trowel. The trowel applicator allows for the liquid moisture barrier to be applied at a perfect thickness. The thicker the better with the moisture barrier. A good way to tell if the liquid moisture barrier is on thick enough is if you can still perfectly read the words on the board it is to thin. All windows, doors, parapets, and control joints are treated with Dryvit’s Aqua Flash ™. (For more information on applying Dryvit’s Aqua Flash ™ visit this post: EIFS Preparations for Rough-Openings Specification)

Before the Exterior Insulation and Finish System drainage came out the styrofoam board was glued to the OSB. The problem with that was when moisture got behind the system there was no protection for the wood and no way for the moisture to get out, so it was trapped behind the system. The result was rotten wood. The drainage system addressed these issues. First there was the cloth barrier between the wood and the foam which helped but did not cure the problems. Then the liquid moisture barrier came out which did finally address the issues with moisture drainage.

EIFS Liquid  Moisture Barrier

EIFS Liquid  Moisture Barrier