Decking · Cold, hard freeze–thaw

How a composite deck ages in Denver, CO

THE SHORT ANSWER

In Denver, sun is the main stress on a composite deck: UV ranks #14 of 25 cities we cover and there are about 42 days above 90 °F. Capped boards lighten noticeably in the first two years, then stabilize; dark colors also get hot underfoot. Model estimate: 23–30 years of service.

Main threat

Sun & UV

Climate profile

Cold, hard freeze–thaw

Expected life

23–30 yrs

Wash

Spring & fall

Rainy days / yr

Days ≥ 90 °F

Simulated composite deck in Denver, CO after 10 years

Year 10Color has lightened, then stabilizes

MODEL SIMULATION

Denver, CO · capped composite boards, south-facing, full sun

Drag through time 0 — 20 years

Color lossHigh

Surface wearModerate

Mildew / rotModerate

Fails first hereColor on full-sun boards

Storyboard

20 years in Denver, washed yearly

Composite deck in Denver, install: Install day — **Install**Install day

Composite deck in Denver, year 1: Slight early fade — **Year 1**Slight early fade

Composite deck in Denver, year 3: Slight early fade — **Year 3**Slight early fade

Composite deck in Denver, year 5: Color has lightened, then stabilizes — **Year 5**Color has lightened, then stabilizes

Composite deck in Denver, year 10: Color has lightened, then stabilizes — **Year 10**Color has lightened, then stabilizes

Composite deck in Denver, year 15: Color has lightened, then stabilizes — **Year 15**Color has lightened, then stabilizes

Composite deck in Denver, year 20: Color has lightened, then stabilizes — **Year 20**Color has lightened, then stabilizes

Denver’s wear fingerprint

Each bar is scaled to the highest of the 25 cities we cover; the black line marks the median.

Rainy days / yr84.4 · Low

Avg humidity49.9% · Low

Decay index34.2 · Low

UV index (avg)1.3 · Typical

Freeze–thaw days135.1 · High

Days ≥ 90 °F42.1 · Typical

NOAA station DENVER-STAPLETON (USW00023062, 10.6 km away), 1991–2020 normals · humidity & UV: NASA POWER.

What fails first here

1Gaps & fastenersBoards expand and contract with temperature — about 135 freeze–thaw days a year here; check hidden clips and end gaps every few years.
2Early color fadeCapped boards lighten in the first 1–2 years, then level off. Stronger here than average: UV rank #14 of 25.
3Heat underfootAbout 42 days a year top 90 °F; dark composite can get uncomfortably hot in full sun. Lighter colors help.
4Surface mildewComposite does not rot, but pollen and dirt on shaded boards feed mildew. A wash in spring and fall prevents it.

Upkeep

Denver maintenance calendar

Built from local normals: bar width is the share of days with rain; composite mainly needs washing.

Jan

Feb

Mar

AprWash & check for mildew

May

Jun

Jul

Aug

Sep

OctWash, clear gaps

Nov

Dec

Same city, other materials

How the alternatives age in Denver

Cedar deck

Expected life here: 14–19 yrs · main threat: freeze–thaw

See it age in Denver →

Wood fence

Expected life here: 13–17 yrs · main threat: freeze–thaw

See it age in Denver →

Pin-ready

Save it for when you build.

The 20-year storyboard as a tall pin, linking back to this page.

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Pinterest storyboard: composite deck in Denver, CO, new to year 20

Composite decks in similar climates

…and in very different ones

Miami, FL

New Orleans, LA

Tampa, FL All 25 cities →

Questions Denver owners ask

How long does a composite deck last in Denver?

Our model puts a capped composite deck at 23–30 years in Denver, close to typical warranty terms. The boards outlast the look: expect some early fading and surface mildew in shade.

How often should you clean a composite deck in Denver?

Twice a year — in spring and fall. Dirt and pollen are the main thing to wash off.

Is composite worth it over cedar in Denver?

In Denver our model gives untreated cedar 14–19 years and composite 23–30. The gap is smaller where rot is slow, so upkeep preference decides.

Why does wood turn white or pale in Denver?

UV breaks down lignin at the surface; rain and wind wash the loose fibers away, leaving a bleached, silvery layer. It is cosmetic until checks open up.

Model simulation, not a guarantee: south-facing, full sun, no shade or ground-contact surprises. How it works.