Thermally Modified Wood for Covered Patio Walls in Portland, ME

Understanding Thermally Modified Wood for Wall Applications

Thermally modified wood undergoes a high-temperature heat treatment process that alters its cellular structure. This modification generally enhances stability and can reduce moisture absorption compared to untreated wood, making it a suitable material for various exterior applications, including covered walls.

For covered patio walls, the primary benefit of thermal modification is its inherent stability, which helps minimize warping, cupping, and checking, especially in environments with seasonal temperature and humidity fluctuations. While covered, these walls are still exposed to ambient moisture and temperature changes.

Selecting the Right Profile and Species

Thermally modified wood is available in several profiles, each offering a distinct aesthetic for covered patio walls. Common options include tongue-and-groove, shiplap, and square edge. The choice of profile influences the shadow lines and overall texture of the finished wall.

Tongue-and-groove profiles provide a tight, interlocking fit, often favored for a clean, continuous appearance. Shiplap creates a distinct overlap with a visible shadow line, adding depth. Square edge boards can be installed with a gap for an open-joint look, though this requires careful consideration of the substrate behind it.

While specific species may vary, thermally modified ash and pine are common. Thermally modified ash, for example, often presents a rich, dark tone and a pronounced grain pattern, while thermally modified pine can offer a lighter, more uniform appearance. The inherent color of the thermally modified wood can be a foundational element for your design, whether left natural or finished.

Finishing Options for Covered Patio Walls

One advantage of using thermally modified wood on covered patio walls is the flexibility in finishing. While it can be left unfinished to weather naturally to a silver-gray patina, applying a finish can help preserve its initial color and offer additional protection.

For a natural wood look, clear sealers or oils can enhance the wood's inherent color and grain. Pigmented stains can introduce a new color while allowing the wood grain to show through. Paints offer opaque coverage for a uniform color. When selecting a finish, consider its UV resistance and maintenance requirements, even for covered areas, as indirect sunlight and ambient moisture can still affect the material over time. Always follow the finish manufacturer's application guidelines.

Attachment and Substructure Considerations

Proper attachment is crucial for the longevity and appearance of thermally modified wood walls. For covered patio walls, a robust substructure is essential. This typically involves horizontal or vertical furring strips, depending on the orientation of your chosen wood profiles, creating a level surface for attachment.

Face fastening with corrosion-resistant screws or nails is a common method for many profiles. For certain tongue-and-groove or shiplap profiles, concealed fastening can be achieved by driving fasteners through the tongue or the lap, creating a clean surface free of visible fasteners. Always pre-drill pilot holes when fastening near board ends to help prevent splitting. Ensure fasteners are appropriate for exterior use and compatible with the wood species.

Adequate ventilation behind the wall cladding is important, even in covered areas, to manage moisture and allow the wood to acclimate. This is typically achieved by using furring strips to create an air gap between the thermally modified wood and the underlying structure.

Worked Example: Designing a Covered Patio Wall

Consider a covered patio in Portland, ME, with a wall section measuring 10 feet wide by 8 feet high, intended to be clad with thermally modified ash shiplap boards. The boards are 6 inches wide (nominal, with a 5.5-inch exposed face) and available in 8-foot lengths.

First, calculate the total wall area: 10 ft * 8 ft = 80 square feet. Next, determine the number of boards needed. Since each board has an exposed face of 5.5 inches (0.458 feet) and is 8 feet long, one board covers 0.458 ft * 8 ft = 3.664 square feet. To cover 80 square feet, you would theoretically need 80 / 3.664 21.8 boards. Rounding up, you would purchase 22 boards of 8-foot length. It's always advisable to add an allowance for cuts and waste, typically 10-15%. For this example, adding 10% would mean 22 * 1.10 = 24.2 boards, so purchasing 25 boards would be a practical approach.

For attachment, if installing horizontally, vertical furring strips would be secured to the existing patio wall structure at regular intervals (e.g., 16 or 24 inches on center). The shiplap boards would then be fastened to these furring strips, typically with concealed fasteners through the overlapping lip to maintain a clean appearance. A clear, UV-resistant oil finish could be chosen to highlight the natural grain of the thermally modified ash while offering some protection from indirect weather exposure.

Before you order

• Determine the desired aesthetic: clean lines (tongue-and-groove), distinct shadow lines (shiplap), or open-joint (square edge).
• Select a thermally modified wood species (e.g., ash, pine) based on desired color, grain, and finish compatibility.
• Choose a finish: natural weathering, clear sealer/oil, pigmented stain, or paint. Consider maintenance.
• Plan the substructure: furring strip orientation (vertical for horizontal cladding, horizontal for vertical cladding) and spacing.
• Select appropriate corrosion-resistant fasteners (face or concealed) and ensure pre-drilling for ends.
• Verify adequate ventilation behind the cladding to manage moisture.
• Calculate material quantities, including waste factor, based on chosen profile dimensions and wall area.

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.

This is a planning guide for projects in Portland, ME. Ask our team to confirm availability, delivery to your ZIP code and which branch can support your order.

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