Overview
Fire-retardant treatment is a building-code subject more than a finishing choice, so this entry is short. It covers the two routes the USDA Wood Handbook (chapter 18) describes: pressure-impregnated fire-retardant-treated wood (FRT) bought from a treater, and fire-retardant coatings applied to finished wood. Neither makes wood noncombustible. Specifications and approvals belong to the building official and the product's listing, not to this guide.
Pros
- FRT reduces flame spread. The Wood Handbook cites the model-code requirement of an ASTM E84 flame-spread index of 25 or less for the treated product.
- Coatings can be applied to existing wood. The Wood Handbook describes intumescent coatings, which swell and char when heated, and non-intumescent coatings. NFPA 703 classes: Class A is a flame-spread index of 25 or less, Class B is 75 or less.
Cons
- FRT does not make wood noncombustible and does not change the rate at which wood chars (Wood Handbook).
- Treatment reduces mechanical properties and can be corrosive to fasteners (Wood Handbook). Arxada, the maker, claims Dricon FS is no more corrosive to fasteners and connectors than untreated wood; that is a manufacturer's claim and the sources differ in tone, so follow the treater's fastener guidance.
- Interior fire-retardant salts are hygroscopic and leach in exterior use; products for exterior use are tested against rain (ASTM D2898, per the Wood Handbook). Wood Handbook: weathered coatings have limited durability.
- FR-treated wood may darken and affect adhesion of finishes.
Suitability
Interior framing, sheathing, trim and exposed timber where the code requires it. The sources I opened do not discuss furniture, so this guide makes no recommendation for it. Outdoor use needs an exterior-rated product; Arxada lists a separate exterior fire-retardant line (FRX) alongside Dricon FS. Check the species approved for the treatment: Arxada says Dricon FS is approved for multiple lumber and plywood species.
Coats and application
FRT is treated at the plant. Finishing: the Wood Handbook says FR-treated wood is generally painted rather than left unfinished because the treatment may darken or discolour wood, and that treatment may interfere with finish adhesion. Test a sample board with your chosen primer and topcoat. For coatings, apply at the film thickness and spread rate the maker's listing states; I did not open a coating data sheet, so this guide gives no figures.
Compatibility
A finish applied over FRT or an FR coating must not be assumed to preserve the rating. Ask the product's maker whether a topcoat is permitted. See Water-based polyurethane, Waterborne acrylic and urethane-acrylic topcoats and Latex and acrylic enamel paint as candidate topcoats to test, not as approved.
Care and repair
Do not cut or drill FRT beyond what the maker allows without checking whether field treatment is needed. If a coating is damaged, repair per the maker. Keep treated wood dry (hygroscopic salts).
Safety and environment
Fire-retardant-treated wood is not fireproof; it can still burn. Sanding and sawing produce dust: wear a dust mask. Disposal: ask the treater and local waste authority; the Wood Handbook says treated wood must not be burned in open fires, stoves or boilers (for preservative-treated wood; check the product label for FRT). US-only guidance; codes vary by jurisdiction.
Related
Example products
Examples, not endorsements; links go to the maker's own site; checked on the date shown.
- Dricon FS fire-retardant-treated wood by ArxadaInterior fire-retardant-treated wood; the maker claims Class A flame spread and a 40-year limited warranty. Maker claims, not independently verified here.Checked 2026-09-30
Suitable for
Broad material kinds: softwood, sheet.
Sources
Updated 2026-09-30. Ratings are relative and drawn from the sources above and manufacturers' data sheets. Test on a scrap of your own wood, and follow the product's own data sheet and safety data sheet.