Composite is a category, not a complete cleaning instruction
A customer says the deck is composite. That is a useful start, but it does not yet identify the care instructions. Trex provides a clear example: its guidance distinguishes early-generation products from named later lines.
Trex's FAQ advises against power washing early-generation products such as Accents, Origins, Brasilia, Profiles and Contours. It says damage caused by that practice is outside the applicable warranty protection. Advice for another board in the same brand is not permission to ignore that warning.
Read the section for the actual product
Trex's current care page describes a conditional pressure-washing method for dirt or mud on Transcend, Enhance and Select decking. It specifies equipment, a fan tip, distance, brushing and thorough rinsing. It also describes hose, soap-and-water and soft-brush cleaning for ordinary dirt.
Those instructions work together. Pulling out a pressure number while leaving behind the named products, nozzle requirement or cleaning sequence changes the advice. This article intentionally links the complete manufacturer instructions rather than presenting one number as a safe setting for all composite decking.
Make identification part of the estimate
Our recommendation is to ask for the invoice, installer information, warranty paperwork or remaining labeled material before preparing a cleaning plan. Record the brand and product line, not just a color description. If identification is uncertain, contact the manufacturer; Trex's FAQ directs uncertain owners to its support team.
Photograph existing damage and ask about previous coatings or treatments. Keep those observations separate from the cleaning recommendation. A contractor can then explain which document applies, what method is proposed and which stains need further assessment, instead of promising a result from the broad word composite.
Do not let a successful test replace identification
A small trial can help evaluate an allowed method, but it cannot establish what an unidentified board is or rewrite its warranty. For a mixed or repaired deck, check whether replacement boards belong to the same product family as the original sections.
The practical takeaway is a repeatable order: identify the material, retrieve its care guidance, resolve uncertainties, and only then choose equipment and products. It takes a little investigation at the start and gives both the owner and the cleaning contractor a clearer basis for the work.
Sources & references
- How to Clean a Trex Deck — Trex. Checked October 25, 2026.
- Trex Frequently Asked Questions — Trex. Checked October 25, 2026.