Support Spacing
Confirm joist spacing and loading for the selected decking profile before framing.
THERMOStart your projectBUILDERS FIRSTSOURCE · ISSAQUAHGet a local Maximo consultation
Exterior Decking & Boardwalks · Division 06 73 00 · Issaquah project guide
Thermo Ashfor Decking.
Thermo Ash is a dense, thermally modified hardwood option for decking and other high-use exterior surfaces. It offers published Class 1 durability and a 20-year Maximo warranty; confirm the warranty terms, span, fastening and maintenance requirements for the selected profile.
APPLICATION SYSTEMThermo Ash · Decking
1,320Janka Hardness
38.5Dry Density
Verify ProductDurability Rating
20 YearMaximo Warranty
Hardware & Nails
Use an approved exterior stainless steel fastening system and pre-drill as directed.
Sub-framing Details
Provide a durable, drained substructure and coordinate joist protection with the assembly design.
Air Cavity Specs
Maintain drainage and airflow below and around the deck; do not trap standing water.
Material & assembly planning
Key advantages &
installation rules.
Real-Wood Surface
Thermo Ash provides the grain, feel and weathering behavior of real hardwood; surface temperature still varies with color and sun exposure.
No Added Wood Preservatives
The thermal process uses heat and steam without adding wood-preservative chemicals.
Dense Hardwood Face
The surface is substantial and can be maintained with cleaning, inspection and compatible finish care.
Assembly Guidelines for Decking:
- Use the current profile guidance to set edge spacing for drainage and expected movement.
- Ensure the area beneath the deck has gravel or slope to prevent standing water accumulation.
- Seal all cut ends with end-grain wax emulsion immediately during installation.
Reduced tangential movement supports more consistent joints through seasonal changes.
Thermal modification reduces moisture uptake and changes nutrients used by decay fungi; confirm the rating for the selected profile.
Real wood modified without added wood-preservative chemicals.
Consultation and order coordination through BFS Issaquah.
Cataloged Profiles
4 Profiles available for
Thermo Ash decking.
1x6 PlusS4S E4E End MatchA dense thermally modified hardwood with pronounced grain and a deep, architectural tone.Compare profile →
5/4x6S4S E4E End MatchA substantial end-matched board built for bold surfaces and high-use exterior spaces.Compare profile →
2x4S4S E4EHardwood strength and dimensional stability in a versatile structural-looking profile.Compare profile →
2x6S4S E4EA broad, solid profile with strong grain for decking, trim and architectural details.Compare profile →Where to buy in Issaquah
Builders FirstSource Issaquah
Catalog available by consultation. Contact the Issaquah team to confirm availability, sample kits, and lead time for your selected Maximo profile.
Issaquah, WA 98029
(425) 391-8000
Monday–Friday, 7:00 AM–4:00 PMDealer information verified August 31, 2026. No in-stock claim is made on this site.
Request a local quote
Put this profile
on your project.
Tell us what you are building. Our team will review your wood selection and contact you to coordinate a Maximo consultation with Builders FirstSource Issaquah.
Frequently Asked Questions
Thermo Ash · Decking
How does Thermo Ash compare to Ipe decking?+
Thermo Ash carries a published Class 1 durability rating and offers a temperate hardwood option with different machining and sourcing characteristics from Ipe. Compare the exact profile, certification, hardness, span and maintenance requirements before specifying either material.
Product and installation references