Two Popular Underlayment Systems to Waterproof Your Roof

We shed light on some important aspects of choosing the right waterproofing solution for your roof. Most can be covered with a single-layer roofing membrane.

Today, there are many materials for waterproofing your roof. In recent years, asphalt and liquid membranes have proven to be efficient, economical, and environmentally friendly. When searching through various roofing “sidings,” as these materials are commonly referred to, roofing contractors realize that not every brand is created equal.

In this article, we explain the two different roof systems to waterproof your roof

Modified / Asphalt Roofing System

Modified asphalt is spread over a fibrous mat, then revitalized on top with granules and on the bottom with powder or a separating adhesive layer. The mat can be fiberglass, polyester, or a combination of both.

Asphalt paper, especially modified asphalt roofing underlayment, provides secondary protection against wind-driven rain, ice barriers, and other forms of moisture intrusion. It can also help the roofing system meet required fire protection requirements and minimize image cropping, which is the visible outline of the deck panels, caused by uneven roof deck thicknesses.

Most roofing today has the benefit of a reflective white color that redirects most of the UV rays and reduces the temperature of the roof during exposure to direct sunlight, known as “cold roofs”.

We use Boral TileSeal HT from Westlake Royal Roofing Solutions – however, there are other modified asphalt roofing underlayment products in the market that can meet your needs. If you need help you can always call us at 602-500-0652

Benefits of using Boral TileSeal

  • Save time and money with self-adhered easy installation
  • Miami-Dade County Approved
  • Stable in low and high temperature climates
  • Suitable for use under all roofing materials – some brands are only meant for metal surfaces.
  • UV resistant
  • Self seals around nails and fasteners
  • 30-Year Limited Warranty
  • Roofers prefer Boral TileSeal because of its superior slip-resistant surface

Experimental Analysis of Waterproof Membranes for Cool Roof Application

An Exhaustive Resource

Study by: ScienceDirect
Buildings are responsible for about the 40% of the global annual energy consumption, therefore, innovative strategies for buildings’ energy efficiency are under development. Strategies of re-roofing with “cool” materials have a non-negligible cooling energy saving potential, as they contribute to the reduction of the peak ambient temperatures during summer

Liquid Roofing System

The first condition to consider when choosing the right material is the compatibility between the existing roof surface and the liquid product you will be using. Ignoring the type of material previously used for shedding cladding can be a costly mistake.

For example, do not apply polyurethane to surfaces that have previously been coated with acrylic elastomer. Solvents found in most polyurethane coatings carry a high risk of acrylic re-emulsification. Another example is a roof that was previously coated with silicone. This type of surface is not suitable for any other type of coating as the silicone surface will interfere with adhesion.

Liquid products must adhere directly to the clean base surface. Debris, grease, dust, or any other substance that breaks down the adhesive between the deck surface and the newly applied liquid material will weaken and adversely affect the performance of the hardened membrane, leading to premature failure.

5 Steps to Consider When Applying a Liquid Roofing System

The following steps must be carried out with the utmost care in accordance with the product manufacturer’s instructions.

Step 1 – Cleaning Pressure washing is the most common method of cleaning an existing roof for surface preparation. Most manufacturers use their own detergents for this purpose, usually biodegradable, or common generic equivalents.

Step 2 – Priming Getting the surface prepared topcoat is crucial. This step also helps block bituminous oils from seeping through the liquid membrane from the existing roof. Before applying most primers, contractors must ensure that the surface is dry. To reduce drying time, contractors usually use aerators or burners.

Step 3 – Detailing Only after the surface is prepared can we apply the liquid membrane – details such as internal and external corners as well as wall-to-floor corners, metal patches and transitions such as pipes, vents, drains, etc. are taken care of during this step.

Step 4 – Base Coat There are two types of liquid membrane applications; some require impregnation of the reinforcing mat during installation, while others do not. Whether a textile mat is mandatory or not, most manufacturers require two or more successive coats to be applied. The consumption rate of each paint and varnish product is indicated in the technical specifications of the manufacturers.

Step 5 – Inspection It is important to observe the thickness of the wet film. Excess liquid product applied at one time will leave uncured material under the peeled membrane surface. Not enough material to provide the required mileage will likely result in premature diaphragm failure. Fish mouths on the edge of the fabric indicate that the reinforcing mat was not properly covered in the overlap area. All errors should be noted and corrected during the professional inspections and review.

Acrylic paints are generally the cheapest, low VOC solution, easy to apply and easy to clean, and can be easily repainted later. Most acrylic roofing systems involve the application of multiple layers of fabric-reinforced coating, which unfortunately lengthens the project. However, their main disadvantage is that acrylic polymers re-emulsify in water, which limits their use on standing water roofs.

Most silicones on the market have good standing water resistance and are relatively easy to install. The main disadvantage for silicone coatings is that it cannot be coated with other liquid products, and coating with the same silicone is often a tedious process that is very expensive in terms of materials and labor. Weather restrictions are another important aspect for property managers and owners to consider.

Most elastomeric and silicone coatings cost between $1 and $3 per square foot of field material. The cost of the work is determined by the amount of time it takes the contractor to complete the waterproofing project. Sufficient time must be allowed for cleaning, substrate preparation and application of the liquid membrane for proper completion to have an accurate labor cost. Sometimes property managers and building owners don’t give enough attention to the reliability, functionality, and importance of the right waterproofing solution for their roofs.

Why Waterproof Your Roof?

The success of any roof waterproofing project always depends on the correct application. “Covering” a roof does not always mean that the roof will be waterproofed. Many coatings serve only the function of protecting the existing roofing membrane from the damaging effects of UV rays, extending its service life. For example, acrylic coatings re-emulsify in water, which leads to complete failure of the product in those areas of the roof where water stagnates.

Building owners and/or property managers should consider using these coverings for maintenance purposes only when the roof has a good positive slope and water does not accumulate around flashing, etc. Even when choosing the right waterproofing membrane, there are many important aspects to consider for a successful waterproofing project. Roofing contractors must adhere to all product manufacturer restrictions and properly manage the correct application. Strictly following the instructions for use is the surest way to ensure that a roof is waterproof.

On roofs where leaks occur, they mostly occur in sections that have not been properly treated. Whether these parts are vents, downspouts, skylights or access to roof HVAC units, parapets and end flashings, these parts are the most vulnerable places where water will eventually seep in and cause damage.

In addition to the application process, proper maintenance throughout the lifetime of a roofing membrane is paramount. Building owners or property managers should consider hiring roofing professionals to perform periodic roof inspections and maintenance work. It is recommended that the cover be inspected at least twice a year to check the proper functioning of the drains, removal of debris, the condition of the membrane and make any necessary repairs as soon as necessary.

Mechanical performance of liquid-applied roof waterproofing systems

In-Depth Research and Analysis

Study by: American Society of Civil Engineers
This study characterizes the mechanical performance of unreinforced and reinforced liquid applied roof waterproofing systems (LARWS) based on several polymer types and links it to the pedestrian accessibility of roofs. The influence of the thickness and of the reinforcement on the system’s performance was assessed on free film samples of cementitious, acrylic, liquid silicone, liquid rubber and polyurethane-based systems.