Flashing is an essential component in protecting a building from water intrusion. It is typically made from metal, such as aluminum or galvanized steel, and is installed around various parts of the structure where water could potentially penetrate, such as roof intersections, chimneys, or skylights. One common method used to seal flashing is by applying tar. In this article, we will discuss whether or not it is suitable to seal flashing with tar, as well as alternative methods that may be more effective.
Understanding the Purpose of Flashing:
Before diving into the topic of sealing flashing with tar, it is essential to understand why flashing is necessary. Flashing acts as a barrier, preventing water from seeping into vulnerable areas of a building. It directs water away from these potential entry points, ensuring that moisture does not penetrate the structure and cause damage such as leaks, rot, or mold growth.
The Traditional Use of Tar:
Traditionally, tar was commonly used in construction for various purposes, including sealing joints, gaps, and cracks. Due to its water-resistant properties, it was also utilized to seal flashing. The application of tar to flashing provided an additional layer of protection against water intrusion.
The Drawbacks of Tar as a Sealing Material:
Although tar was widely used in the past, there are several drawbacks associated with its use as a sealing material for flashing:
- Durability: Over time, tar may degrade and become less effective, especially under the harsh conditions of weather exposure. This can lead to the need for frequent reapplication or maintenance.
- Temperature Sensitivity: Tar has a limited temperature resistance, as it can soften and lose its sealing ability in high temperatures. Conversely, in colder temperatures, tar may become too brittle, compromising its effectiveness.
- Flexibility: Flashing materials, particularly metal flashing, can expand and contract with temperature changes. Tar, on the other hand, tends to harden and lacks the flexibility required to accommodate these movements. This rigidity can result in the separation of the flashing from the structure, leading to potential leaks.
Modern Alternatives to Tar:
Considering the drawbacks of tar as a sealing material for flashing, modern construction practices have introduced alternative methods that are more durable and effective:
- Adhesive Flashing Tapes: These tapes are specifically designed for sealing flashing and are made from rubberized asphalt or butyl rubber compounds. They are highly flexible, weatherproof, and provide a reliable seal around flashing without the need for additional adhesives or sealants.
- Sealants: High-quality, elastomeric sealants, such as silicone or polyurethane, have become widely used in sealing flashing. These sealants offer excellent adhesion to different substrates and maintain flexibility over a wide range of temperatures. They create a durable and watertight seal when correctly applied.
- Self-Adhering Membranes: Some membranes, such as a self-adhering bituminous membrane, are designed for flashing applications. These membranes have a sticky backing that adheres directly to the surface, creating a reliable seal against water intrusion.
While tar was historically used to seal flashing, it has several drawbacks that make it less ideal in modern construction practices. Today, adhesive flashing tapes, sealants, and self-adhering membranes offer more durable and flexible alternatives for effectively sealing flashing. These modern materials provide superior protection against water intrusion and can withstand the challenges of weather exposure, ensuring the long-term integrity and performance of the building envelope.