Order Samples

Hewn’s Class A Ignition-Resistant Cedar Siding maintains the visual look and feel of our traditional exterior cedar siding, while implementing an industry-leading fire treatment process that modifies the wood to its core. These products resist the spread of fire, helping your project meet any major fire codes present in your area, and protecting your property in ways that were previously out of reach on a commercial scale. 

In addition to their ignition resistant properties, our treatment process has the added benefit of slowing the aging process of the wood itself, protecting against ultraviolet degradation and extending the lifetime of the material. 

Our ignition resistant products are subjected to industry-standard accelerated weathering tests (ASTM D-2898), Flame Spread (ASTM D-84), and are verified by International Code Counsel ESR-1159 and ESL-1021.

Custom Options

Hewn’s Class A Ignition-Resistant Cedar Siding can be customized to fit the individual needs and specifications of your particular project. Our finely skilled craftsmen can modify nearly any part of our in-house process to create a material designed according to your specifications, and our color technicians can match any shade or tone provided to us as part of our custom sampling process. Please contact a Hewn sales representative for more information.


Wood Species

Western Red Cedar


Select Tight Knot

Standard Thickness


Standard Widths (Nominal)

1×4, 1×6, 1×8, 1×10, 1×12

Milling Profile

Tongue & Groove or Shiplap (Multiple Options)

Moisture Content

Kiln Dried – Average 10-14%

Fire Resistance

Hewn Thermex-FR®

Process Type

Vacuum-Impregnated Treatment

Class Rating

Class A (ASTM E84)

Possible LEED Credits

MR 5 – Regional Materials

Flame Spread Index

25 (or less)

V.O.C. Content

< 550 g/L

Smoke Developed Index

45 (or less)

Testing Lab

QAI Laboratories

Report Number

IAS Report No. AA-635

Treatment Notes

ICC ES Report ESR-1159 ESL 1021. Tested per ASTM E84 / UL 723. Extended for 30 min, no increase in listed classification subjected to standard rain test (ASTM D2898). KDAT.

View Class A Ignition-Resistant Cedar Siding