Need WUI and Fire Code Ready?
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The Goal: Getting a natural, modern wood ceiling on public entryways or residential soffits while staying strictly within fire codes. Especially in WUI (Wildland-Urban Interface code) areas and where Class A fire resistance is mandated.
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The Expert Choice: SaferWood fire retardant treated wood (FRTW) . This fire retardant is not a surface treatment but is molecularly bonded with the wood, so eliminates the need for additional fire retardant backing. It won't wash off or leach, even in harsh weather. And it's available in several of the most specified Mataverde and Arbor Wood options, and dimensional lumber.

Photo courtesy of T. J. McCartney, Inc.
Mataverde SaferWood thermally modified Hemlock fire-retardant treated wood siding covers a large exterior atrium in Massachusetts that extends "through" the glass wall to the wood ceiling entryway.
Installation Logistics: Engineering the Ceiling Grid
We know the "how" is just as important as the "what." Here is some actionable guidance for the crews in the field.
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Load Requirements: Premium hardwoods are gorgeous but heavy. Mataverde and Arbor Wood thermally modified woods still have the strength and looks you need but weigh much less. Thus making them easier to transport on site and handle in high places.
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Fastener-Free Results: Using the Climate-Shield Wood Rainscreen hidden clip system isn't just about looks, it’s about labor. The Climate-Shield clips eliminates the need for a grid of furring strips behind the soffits. It also eliminates face-screwing and plugging hundreds, (or thousands), of feet of planks, keeping your timeline on track and your labor costs down.
This interior to exterior illusion of a wood ceiling soffit was created with Climate-Shield Wood Rainscreen System
Master Level Material Specification Criteria
We understand that choosing the right types of wood for ceiling and soffit projects involves more than just picking a color. Let's look at the metrics that matter most to your project's success.
Stability > Everything Else
The look of soffits is as critical as that of siding. Warping, cupping, and twisting often plague standard wood ceiling planks in both interior and exterior locations. Specifying the best thermally modified wood for the environment is the best way to handle material movement.
Mataverde and Arbor Wood thermally modified woods undergo a patented process that resolves these common issues. These selections are available in several profiles including rainscreen. By treating with patented heat and steam, the result is a less brittle, more resistant lumber with improved strength.
Durable and resilient Arbor Wood BRNSH burned, brushed and black oil finish pine siding was used to create this addition with deep soffits and surrounds on the balconies and entryways.
What About Sustainability & Sourcing?
These materials aren't just high-performing; they are environmental responsible, fully recyclable, and help reduce the carbon footprint of your build. All of the thermally modified wood siding options we offer are sustainably sourced and harvested.
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Mataverde ThermaWood is domestically sourced from A+ Better or C+ Better Western Hemlock.
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Arbor Wood is a 100% US-sourced and produced wood siding material.
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The thermal modification process is chemical-free and non-toxic to the environment.
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If FRTW is needed, Thermex-FR fire-retardant treatment is environmentally safe for humans and the environment, never sheds or washes off, and is non-leaching.
Below, thermally modified Thermex-FR treated wood leaving the high pressure kiln.jpg?width=973&height=573&name=Mataverde%20SaferWood%20ThermaWood%20Hem-Fir%20leaving%20the%20vacuum%20kiln%20(landscape).jpg)
Types of wood for ceiling soffits:
Arbor Wood Co.
Thermowood Thermally Modified Ash - Premium Clear, shown with oil finish
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1x4 cladding profile |
1x6 cladding profile |
Thermowood Thermally Modified Pine - C or Better Clear, shown with oil finish
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1x6 (3/4 x 5 actual) cladding profile |
5/4x6 (1 x 5 actual) |
Interested in pricing an upcoming project? Let us know the details here:
Thermowood BRNSH burned finishes - a new take on Shou Sugi Ban
Burned Pine with black oil finish (with "alligator skin char" texture) |
Burned and brushed pine with black oil finish |
Burned and brushed pine with brown oil finish |
Mataverde ThermaWood
ThermaWood Hem-Fir T&G Reversible
ThermaWood Hem Fir in T&G Nickel Gap

Fire Safety Without Compromise:
Mataverde SaferWood is a thermally modified fire-retardant treated wood (FRTW) that can help navigate strict building codes, including commercial spaces and WUI (Wildland-Urban Interface) zones.
Using SaferWood FRTW ensures your wood ceiling porch or entryway:
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meets Class A Flame Spread and ignition-resistant ratings.
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has a permanent, non-toxic, chemical-free treatment (Thermex-FR) that is safe for both people and the environment.
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has the only FRTW to pass the California 10-Year Weathering Test, making it an ideal choice for exposed soffits.
Mataverde SaferWood ThermaWood Fr Hemlock
Ready? Request a SaferWood FRTW project quote here:
or T&G or Rainscreen quotes here:
SaferWood
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Mataverde STK (Select Tight Knot) FR Western Red Cedar Siding
1x6 nominal, 11/16" thick x 5" width (coverage) T&G
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Mataverde ThermaWood FR Hemlock 633 T&G reversible
1x6 nominal, 11/16" thick x 5" width (coverage)
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Mataverde ThermaWood FR Hemlock Nickel Gap T&G
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Mataverde ThermaWood FR Hemlock Rainscreen
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Arbor Wood FR Pine Nickel Gap T&G
1x6 nominal, 3/4" thick x 5" width (coverage)
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Arbor Wood FR Ash Nickel Gap T&G
1x4 cladding profile |
The Bottom Line (Value Engineering):
It’s about more than the initial bid. Premium wood finished ceilings offer a smarter lifecycle cost by drastically reducing long-term maintenance, refinishing, and the need for premature wood soffit replacement. Plus, it is recyclable when no longer in use.
Final Verdict: Elevating Your Next Project
While premium systems like these represent a higher initial commitment than drywall, the reward has to be clear. Between the unmatched stability, the impact of the design, and the fact that these woods are near zero maintenance, a thermally modified wood ceiling soffit is a high-value upgrade for any professional specification.
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Arbor Wood Ash cladding was used to cover the deep angled overhang and bring together the interior and exterior design - which incudes Ash siding and decking.
High-impact architectural visual with Arbor Wood Ash first floor main entrance and deep window surrounds on the second floor
Mataverde Thermawood T&G Hemlock interior ceiling over a kitchen
Thermally modified wood for soffits and floors are uniquely suited for moisture rich environments like saunas and indoor pools 









