Thermally Modified Ayous and Rainscreen Assemblies: Specify the Whole Wall

What is a Rainscreen and Why Does it Matter for Ayous?

A rainscreen system functions on the principle of a pressure-equalized or ventilated cavity. The outer cladding, in this case, Thermally Modified Ayous, acts as a primary rain screen, deflecting most wind-driven rain. Any water that bypasses the cladding drips down the back surface of the Ayous and drains out at the base of the wall. The air cavity behind the cladding also allows for ventilation, promoting drying of the entire wall assembly.

Thermally Modified Ayous is a lightweight wood known for its improved dimensional stability after thermal modification. While this modification enhances its resistance to moisture and movement compared to untreated wood, it is still a natural material. Integrating Ayous into a rainscreen assembly provides an additional layer of protection, managing moisture effectively and contributing to the longevity of the cladding and the building envelope. This approach helps maintain the aesthetic integrity of the Ayous over time by minimizing prolonged exposure to trapped moisture.

Key Components of a Rainscreen Assembly

A complete rainscreen assembly typically includes several layers working in concert:

1. **Structural Wall:** This is the core of your building, often sheathing over studs.

2. **Weather-Resistant Barrier (WRB):** Applied directly over the structural sheathing, the WRB is the primary defense against water penetration. It must be continuous and properly flashed around openings to prevent water from reaching the structural components.

It allows water to drain down and air to circulate, facilitating drying.

4. **Furring Strips:** These strips create the drainage cavity and provide a secure attachment point for the cladding. They are typically installed vertically for horizontal cladding or horizontally for vertical cladding, ensuring proper drainage. The depth of the furring strip defines the cavity depth.

5. **Thermally Modified Ayous Cladding:** The visible exterior layer, offering aesthetic appeal and initial weather protection. Common profiles for cladding include S4S E4E (square edge) or V-Joint/Nickel Gap, which offer distinct visual lines and installation methods.

Designing the Drainage and Ventilation Cavity

The effectiveness of a rainscreen largely depends on the drainage and ventilation cavity. Adequate top and bottom ventilation openings are crucial for this airflow.

For horizontal Thermally Modified Ayous cladding, vertical furring strips are installed over the WRB. This ensures that any water reaching the cavity can drain freely downwards without being trapped by horizontal supports. For vertical Ayous cladding, horizontal furring strips are often used, with additional vertical strapping or a drainage mat to maintain a continuous drainage plane behind the cladding.

Consider using insect screens at the top and bottom of the cavity to prevent pests from entering the system while still allowing air movement. The specific design of the cavity, including furring strip dimensions and ventilation details, should be determined by a qualified professional to meet local building codes and performance requirements.

Choosing the Right Thermally Modified Ayous Profile for Rainscreen

Thermally Modified Ayous is available in several profiles suitable for rainscreen applications. The choice of profile impacts the aesthetic and how the cladding interacts with the rainscreen system.

When installed horizontally, the eased edges can create subtle shadow lines. For a more defined shadow line or a tighter joint that still allows for drainage, V-Joint or Nickel Gap profiles are often selected. These profiles are designed to create consistent spacing and visual effects.

When planning your rainscreen, consider the chosen profile's nominal size. The actual dimensions will be slightly smaller than nominal, which is important for precise layout and material takeoffs. Regardless of the profile, ensuring proper fastening to the furring strips is essential for the stability and performance of the cladding.

Explore options for Thermally Modified Ayous profiles: [Product Link: /thermally-modified-wood/ayous]

Worked Example: Designing a Rainscreen with Thermally Modified Ayous

Let's consider a hypothetical wall section, 10 feet wide by 8 feet high, to be clad with horizontal Thermally Modified Ayous S4S E4E 1x6 nominal boards. The goal is a rainscreen assembly with a 3/4-inch drainage cavity.

**1. Weather-Resistant Barrier (WRB):** First, the structural sheathing would be covered with a continuous, properly lapped and taped WRB, ensuring all openings (windows, doors) are correctly flashed.

**2. Furring Strips:** To create the 3/4-inch cavity, we would use vertical furring strips, such as 1x3 (actual ~3/4 inch x 2.5 inch) lumber, installed at 16 or 24 inches on center. These strips would be fastened through the WRB into the structural studs.

**3. Cladding Installation:** The Thermally Modified Ayous 1x6 S4S E4E (actual dimensions closer to 3/4 inch x 5.5 inches) boards would then be installed horizontally, fastened into the vertical furring strips. For an 8-foot high wall, you would need approximately 18 boards (96 inches / 5.5 inches per board = ~17.45 boards). Allowing for a small reveal between boards, this would be 18 boards.

**4. Ventilation and Drainage:** At the bottom of the wall, a starter strip and insect screen would be installed to allow drainage and ventilation while preventing pests. A similar detail would be incorporated at the top of the wall, often integrated into a soffit or trim detail.

This example illustrates the layers and considerations. Actual measurements, specific product dimensions, and detailed flashing plans are critical for a successful installation.

Before you order

• Have I confirmed the required depth of the drainage cavity based on local codes or architectural specifications?
• Is the chosen Weather-Resistant Barrier compatible with the climate and structural wall type?
• Are the furring strips adequately sized and spaced to support the Thermally Modified Ayous cladding and create the desired cavity?
• Have I accounted for proper ventilation openings at the top and bottom of the rainscreen cavity, including insect screens?
• Is the Thermally Modified Ayous profile (e.g., S4S E4E, V-Joint/Nickel Gap) appropriate for the desired aesthetic and installation method?
• Have I planned for proper flashing details around all windows, doors, and penetrations to integrate with the WRB and rainscreen cavity?
• Will fasteners used to attach the Ayous cladding penetrate only the furring strips and not compromise the WRB?
• Have I considered the overall system and consulted with a qualified professional for structural and moisture management advice?

Confirm installation details, approved uses and warranty terms in the current instructions for the exact product and profile. Your installer should verify the substrate, structure and applicable project requirements.

Questions to help you decide

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