One strip of decking looks distorted. The surrounding boards seem ordinary. Then, at a particular hour, a bright rectangle slides across exactly that spot. The afternoon has supplied a useful clue.
Differentiate ordinary sunshine from a reflection
AZEK's technical bulletin warns that reflected light from some energy-efficient glazing can produce unusually high surface temperatures and damage exterior materials. This is different from a deck simply feeling hot under bare feet.
Document the moving pattern
From a safe position, photograph the reflection, affected boards, and time of day. Share the product identities with both manufacturers. Ask about a compatible way to reduce the reflection and any warranty implications. Review window-film compatibility with the actual glazing. Do not apply an arbitrary film to the window or experiment by concentrating light on another sample.
| Record | Example entry | Why it matters |
|---|---|---|
| Date and sky | Clear afternoon; note season | The path changes through the year |
| Start / strongest / end | Record actual observed clock times | A morning inspection may miss it |
| Location | Mark affected board numbers on a photo | Links the bright patch to the damage |
| Possible reflector | Window above the same run | Manufacturer can review glazing identity |
| Changes nearby | New glazing, screen removed, pale furniture moved | Avoid blaming the wrong surface |
Sun to glazing
Identify the window receiving direct sunlight at the problem time.
Glazing to deck
Photograph the moving bright patch without staring into the glare.
Deck surface
Compare its track with distorted boards, including unaffected neighbours.
Ask the decking supplier whether the observed damage fits heat exposure and ask the window supplier about an exterior screen or other compatible shading arrangement. The AZEK bulletin discusses screens and reflection-reducing measures. Obtain a proposal for this glazing: a dark film, interior blind or improvised cover is not an interchangeable remedy. Keep the original photos and affected-board details for the warranty review.
Before the next step
- Record when and where the bright patch appears.
- Check both window and decking product details.
- Settle the heat-source remedy before ordering replacement boards.
Resolve the reflection before paying for another board. If the whole deck simply feels hot underfoot, that's a different decision: compare ordinary deck heat, colour, and shade before blaming a window.