The exterior walls of a building, often referred to as the building envelope, are under constant attack from the elements. No matter how high-quality the stucco, brick, stone, or siding, water penetration is inevitable. Once moisture bypasses the outer cladding, it becomes trapped against the sheathing and framing, leading to a destructive cycle of mold growth, rot, and structural degradation.

The solution mandated by modern building science and code—a properly engineered rainscreen system—is critical to achieving long-term durability. Mortairvent® Rainscreen is the industry-leading drainage mat specifically designed to solve the wall moisture problem by creating a high-performance, continuously drained, and ventilated air gap. This detailed review explains exactly how Mortairvent works to safeguard the health and longevity of your walls.

1. The Core Principle: Eliminating Trapped

Moisture with an Air Gap

Water intrusion, primarily from wind-driven rain and capillary action, is responsible for over 90% of all exterior wall failures. Traditional construction often relies on a flat weather-resistant barrier (WRB), which is simply not enough. The WRB stops water, but it doesn't provide a path for the moisture to escape once it gets behind the cladding.

Mortairvent® Rainscreen is engineered to physically separate the cladding from the WRB, achieving the three critical functions of a high-performance wall:

A. Capillary Break and Drainage Plane

Mortairvent is a three-dimensional drainage mat featuring a highly open, non-woven polymer core. With a remarkable 93% to 95% open design, it creates a continuous air gap (available in thicknesses like 6mm or 10mm) between the exterior finish and the underlying sheathing.

• Capillary Action Halted: The air gap physically breaks the adhesive forces that would otherwise allow moisture to wick directly into the wall components.

• Gravity Drainage: Any bulk water that penetrates the cladding drops onto the surface of the Mortairvent matrix, where gravity efficiently channels it down and out of the wall system through weep holes at the base. This rapid drainage is key to preventing water accumulation.

B. Accelerated Convective Drying

The continuous airspace established by Mortairvent Rainscreen encourages constant airflow. This ventilation is essential for convective drying.

• Air flows freely through the vertical channels, creating a "chimney effect." As solar radiation heats the cladding, moist air rises and is exhausted at the top of the wall, drawing in drier air from the bottom.

• This process effectively removes trapped water vapor from the surface of the WRB and the back of the cladding, minimizing the time the wall spends wet and drastically reducing the risk of mold and mildew growth.

2. Mortar Deflection: Protecting Masonry

Applications

One of the most valuable features of Mortairvent is its specialized two-ply design, making it the superior stucco drainage mat and solution for adhered masonry veneer.

• The Problem with Mortar: When applying claddings like brick, stone, or stucco, excess mortar (or "droppings") inevitably falls behind the veneer. If this mortar is allowed to cure within the main drainage channel, it creates "mortar bridges" that clog the system, effectively neutralizing the benefits of the airspace.

• The Mortairvent Solution: Mortairvent features a heat-bonded filter fabric on its exterior surface. This fabric acts as a mortar deflection layer, catching the droppings and holding them away from the blue polymer core.

• Clean Drainage Path: By blocking mortar, the fabric ensures that the 95% open drainage channel remains fully functional and unobstructed for the entire life of the wall, guaranteeing continuous water shedding and ventilation.

3. Code Compliance and Engineered

Integrity

The use of rainscreen drainage mats is quickly becoming mandatory, especially in Moist (A) and Marine (C) climate zones.

• Meeting IRC Standards: Mortairvent meets or exceeds the most stringent requirements, including the 2021 International Residential Code (IRC) Section R703.7.3.2, which often requires a drainage material of at least 3/16 inch (5mm) in depth, or a tested drainage efficiency of 90% (Mortairvent is tested to ASTM E2925).

• Durable Polymer Construction: The material is a durable, non-degrading polypropylene (polymer) core. It is resistant to corrosive chemicals found in the soil and is inherently resistant to providing a food source for mold or mildew. This structural integrity ensures the product functions effectively for the entire 25-year limited warranty period.

• Integrated Insect Screen: A crucial detail for maintaining the air gap's functionality is pest control. Mortairvent features a built-in flap that can be folded at the top and bottom of the wall assembly during installation, creating an effective integrated insect screen that keeps pests out while allowing air and moisture to flow freely.

4. Versatility and Cost-Effectiveness

Mortairvent® Rainscreen is a single, versatile product that streamlines the construction process for multiple cladding types, ensuring a high level of wall moisture protection across the board.

• Universal Application: Effective with virtually all exterior materials:

  • Stucco and Adhered Masonry: Mortar deflection is essential.

  • Brick Veneer: Prevents cavity blockage.

  • Wood/Cedar Siding: Ensures drying on the back face to prevent warping and staining.

  • Fiber Cement/EIFS: Provides a reliable secondary drainage path.

• Faster, Cheaper Installation: Unlike traditional methods that rely on labor-intensive wood furring strips, Mortairvent is a lightweight, easy-to-handle roll. It is simply unrolled over the WRB and fastened with staples or nails, significantly reducing labor time and construction costs.

• Protecting Curb Appeal: By maintaining a dry wall cavity, Mortairvent prevents the cosmetic damage caused by trapped moisture, such as the staining, peeling, and blistering of exterior finishes, preserving the building's aesthetic appeal and market value.

The Definitive Choice for Building

Envelope Resilience

In modern construction, the wall system must be designed to manage water, not just repel it. Mortairvent® Rainscreen provides the engineered capillary break and drainage channel necessary to ensure your wall assembly remains dry and healthy, eliminating the primary causes of structural failure, health hazards, and costly repairs.

By installing this high-performance rainscreen drainage mat, you are securing a durable building envelope that complies with the strictest moisture codes and delivers peace of mind for decades.

Order Now at spycorbuilding.com for the full line of Mortairvent® Rainscreen products and accessories.

Frequently Asked Questions (FAQ)

Does Mortairvent replace the Weather-Resistant Barrier (WRB) or house wrap?

No. Mortairvent Rainscreen is installed over the WRB (house wrap, asphalt felt, etc.). It acts as the final component that creates the critical air gap for drainage and ventilation, working with the WRB to ensure comprehensive wall moisture protection.

What different thicknesses of Mortairvent are available?

Mortairvent is commonly available in several thicknesses, including 6mm (0.25 inches), which meets the new 5mm IRC code requirement, and 10mm (0.40 inches), which offers even more robust drainage and ventilation, particularly for high-exposure areas or the Canadian building code.

How does Mortairvent create an insect screen?

During installation, the filter fabric on the top and bottom edge of the Mortairvent roll is folded and tucked back between the blue polymer matrix and the WRB. This simple, integrated feature creates a fine mesh barrier that prevents insects from entering the drainage cavity while still allowing air and moisture to exit.

Why is the filter fabric on Mortairvent so important for stucco?

The filter fabric serves as a mortar deflection layer. It prevents mortar droppings from stucco, stone, or brick from falling into and hardening inside the 95% open blue polymer core. This ensures the drainage and ventilation channels remain clear and fully functional, a necessity for stucco drainage mat applications.

Is Mortairvent a good option for sustainable construction?

Yes. Mortairvent is often made with recycled content and its non-degrading polymer material is resistant to mold and corrosion. Its use in managing moisture and improving the durability of the building envelope can contribute to achieving LEED credits for sustainable design.