Choosing Thermally Modified Ash for a Renovation: What to Check First

Evaluating the Existing Substructure

The integrity of the existing substructure is a primary concern for any renovation involving a new cladding or ceiling material. Before installing thermally modified ash, inspect the framing, sheathing, and any existing furring strips or rainscreen components. Look for signs of rot, insect damage, or structural instability.

Thermally modified ash, like other cladding materials, requires a sound and level surface for proper installation. If the existing substructure is compromised, it may need repair or replacement. This could involve reinforcing studs, replacing damaged sheathing, or leveling uneven surfaces. A professional inspection can help identify hidden issues that might impact the longevity and performance of the new material.

Assessing the Wall Assembly and Moisture Management

Understanding the existing wall assembly is critical for ensuring proper moisture management. This includes identifying the type of weather-resistive barrier (WRB), air barrier, and any existing drainage planes. Thermally modified ash is often specified for rainscreen applications, which incorporate a ventilated air gap behind the cladding to promote drainage and drying.

If your renovation project does not currently have a rainscreen assembly, integrating one should be a key consideration. This typically involves installing furring strips over the WRB to create the necessary air space. Thermally modified ash's improved stability helps it perform well in exterior applications, but it still benefits from a well-designed moisture management system to protect the underlying structure. The "S4S E4E End Match" profile in "1 × 6 Plus" and "5/4 × 6" nominal sizes are common choices for siding applications. The "S4S E4E" profile in "2 × 4 and 2 × 6" is also noted for decking and structural details.

For interior applications, such as a feature wall or ceiling, moisture management concerns are generally reduced, but proper ventilation and a stable substrate are still important.

Compatibility with Existing Materials and Finishes

Consider how thermally modified ash will interact with other existing or new materials on the project. This includes adjacent siding materials, trim, windows, doors, and roofing. The deep brown hue of natural thermally modified ash offers a distinct aesthetic that can complement various architectural styles. It has a pronounced grain and denser feel.

If you plan to apply a finish, consider how it will age alongside existing finishes. Thermally modified ash can be left unfinished to weather naturally to a silver-gray patina over time, or it can be finished with stains or oils to maintain its initial color. Ensure that any chosen finishes are compatible with both the thermally modified ash and any adjacent materials.

Planning for Profiles and Applications

Thermally modified ash is versatile, suitable for cladding, ceilings, feature walls, and selected decking details when the specified profile and installation system are confirmed. The available profiles include S4S E4E End Match in 1 × 6 Plus and 5/4 × 6 nominal sizes for siding, ceilings, and decking. For more robust applications like decking and structural details, S4S E4E in 2 × 4 and 2 × 6 nominal sizes are available. Trim and molding can utilize S4S E4E in 1 × 10, 2 × 2, 2 × 4, and 2 × 6.

When renovating, consider whether the desired aesthetic and functional requirements align with these available profiles. For example, if you are replacing a wide board siding, a 1 × 6 Plus profile might be a good match. If you are creating a new ceiling feature, the end-matched profiles can simplify installation and create a continuous look. The decision to use thermally modified ash should confirm that the chosen profile and its intended application are supported by the product's specifications.

Hypothetical Renovation Example: Decking Upgrade

Imagine a homeowner wants to renovate an existing 10-foot by 12-foot elevated deck. The current decking boards are aging pressure-treated pine and the substructure (joists and beams) is in good condition. The homeowner desires a more stable and aesthetically appealing hardwood surface.

The existing ledger board is securely attached, and there are no signs of rot on the substructure. The homeowner chooses thermally modified ash with an S4S E4E profile in 5/4 × 6 nominal size for the decking.

For a 10-foot by 12-foot deck, the area is 120 square feet. With 5/4 × 6 boards (actual width approximately 5.5 inches), each linear foot covers approximately 0.458 square feet (5.5 inches / 12 inches per foot). To cover 120 square feet, approximately 262 linear feet of decking would be needed (120 sq ft / 0.458 sq ft per linear foot). Allowing for cuts and waste, purchasing around 290-300 linear feet would be a reasonable starting point. This calculation is for material coverage only and does not account for specific board lengths or a detailed cut plan, which would be refined during the actual ordering process.

This renovation would involve carefully removing the old decking, inspecting and potentially cleaning the substructure, and then installing the new thermally modified ash boards using appropriate fasteners. The improved moisture response of thermally modified ash would be a benefit in this outdoor application.

Considering the Broader Project Goals

Beyond the technical aspects, consider how thermally modified ash aligns with your overall renovation goals. Does it fit the desired aesthetic? Is the budget realistic for the material and installation? While thermal modification enhances stability and provides a hardwood presence, it is important to confirm that these benefits align with the project's priorities.

For example, if the goal is a rapid, superficial refresh, extensive substructure work might push the project beyond its scope or budget. If the goal is a durable, long-lasting exterior with a distinct natural appearance, thermally modified ash is a strong candidate, provided the underlying conditions are addressed properly.

Before you order

• Is the existing substructure sound and free from damage (rot, insects)?
• Is the existing wall assembly suitable for thermally modified ash, including a weather-resistive barrier?
• Will a rainscreen assembly be incorporated or improved for exterior applications?
• Are the chosen thermally modified ash profiles suitable for the intended application (cladding, ceiling, decking)?
• How will thermally modified ash interact aesthetically and functionally with existing adjacent materials?
• What is the plan for finishing or allowing the material to weather naturally?
• Does the overall project budget account for any necessary substructure repairs or assembly upgrades?
• Are the project timelines realistic given potential substructure work?
• Is professional consultation needed for structural or moisture management assessments?

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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