Rooftop Waterproofing

What to do before waterproofing a rooftop

A large section of a flat roof covered two or three decades ago with single-ply roofing membranes. Replacing an old roofing system today is expensive, but liquid applied roofing systems have emerged as reliable alternatives to the market over the past few years.

The first condition that must be met in choosing the right material is the compatibility between the current roof surface and the liquid product used.

Ignoring materials previously used to stain single-ply ceilings are an expensive mistake. For example, placing urethane on a surface coated with acrylic elastomeric is a bad idea. Solvent containing most urethane coatings present a high risk of re-emulsification for acrylic. Another example is a roof covered with silicone. This type of surface does not accept other types of coatings, as the silicon prevents surface adhesion.

It is also important to clean the substrate properly before waterproofing the flat roof. Whether it’s a new or an existing roofing system, this procedure is important because liquid products must adhere directly to a clean bare substrate surface.

As a result, a substrate that is not properly cleaned can adversely affect the function of the healed membrane, leading to its initial failure. Pressure washing is the most common method of cleaning an existing roof for surface preparation. Most manufacturers specify their own detergents, typically biodegradable or widely accepted for this purpose.

Steps to waterproof a rooftop

The classic application of liquid applied roofing membranes consists of four main steps, all of which must be treated with extreme importance following the product manufacturer’s instructions. These steps include cleaning, priming, detail treatment, coating application, and inspection.

1) The first step to rooftop waterproofing is to clean the surface.

Good adhesion is required for all successful liquid membrane applications. For this reason, proper cleaning is as important as the actual proper application of the liquid.

In general, pressure washing is the most common method to clean the surface. This process avoids the so-called bond breakers. In addition, it finds details of treatments that may not appear at first glance.

2) The second step is after cleaning

Surface priming is designed to improve membrane adhesion. Primers help prevent the bleeding of bituminous oils through the liquid membrane from the existing roof.

Before applying most primers, the contractors must confirm that the surface is dry. To reduce drying time, contractors usually use an air blower or a flashlight.

3) The third step is the treatment of details.

Contractors need to take care of all the details, they resume field application of the liquid layer. Details such as the inner and outer corners, as well as wall-to-floor corners, metal flashing terminations, and pipes, drains, etc., usually reinforce fabric embedded in a liquid membrane.

4) The application of the liquid membrane

There are two applications types of liquid membranes. Regardless of whether fabric mats are mandatory, most manufacturers require a coating application in two or more consecutive layers. The consumption rate of each coating product is specified in the manufacturer’s technical specifications.

The method of application, surface porosity, temperature, and waste are external factors that affect the specified consumption rate.