How old are homes in Westmont, and what does that mean for a deck?
14% of homes in Westmont's covered ZIP code were built in 2000 or later and 19% before 1960; the largest group dates to the 1970s.
Homes in Westmont have a median construction year of 1976, so a deck original to a typical house would now be about 50 years old — beyond the point where wood framing, fasteners and flashing can be assumed sound.
Many decks from the 1970s and 1980s were built before today's detailed deck provisions appeared in model codes. Common issues on decks of this age include corroded hangers, posts set directly in soil and ledger boards fastened with nails. Replacement is often the better value than repeated repairs.
That is about the same as DuPage County overall (median 1978). Statewide, the median Illinois home was built in 1971. Among the 102 covered Illinois communities with Census data, Westmont ranks #56 for oldest housing. In this ZIP code, 19% of homes were built before 1960, 43% between 1960 and 1979, 25% between 1980 and 1999, and 14% since 2000 — the single largest group dates to the 1970s.
| Decade built | Homes | Share |
|---|---|---|
| 2020 or later | 154 | 1% |
| 2010s | 238 | 2% |
| 2000s | 1,164 | 10% |
| 1990s | 1,099 | 10% |
| 1980s | 1,756 | 15% |
| 1970s | 2,996 | 26% |
| 1960s | 1,886 | 17% |
| 1950s | 1,295 | 11% |
| 1940s | 231 | 2% |
| before 1940 | 607 | 5% |
What does Westmont's climate mean for deck construction?
Westmont averages about 144 days a year at or below freezing, 42.3 inches of snow and 39.7 inches of precipitation, based on NOAA 1991–2020 normals.
The nearest NOAA climate station with 1991–2020 normals is Lisle-Morton Arboretum, about 5 miles away. It records an average of 144 days a year with a low at or below 32°F — a long, hard freezing season. On roughly 98 of those days the temperature climbs back above freezing, so water in wood, soil and gaps between boards repeatedly freezes and thaws.
For Westmont, that means footings must bear below the locally required frost depth to avoid heaving, and wood surfaces should be kept sealed so absorbed water doesn't split boards over winter. Synthetic decking tolerates freeze-thaw well but still needs the manufacturer's expansion gaps.
Snow is a major factor: the Oak Brook 2w station averages about 42.3 inches a year. Framing has to carry snow load, stairs need a plan for winter use, and snow removal should be done with plastic-bladed shovels and ice-melt products the decking manufacturer allows.
Westmont sees about 39.7 inches of precipitation a year, with measurable rain or snow (0.1 inch or more) on about 76 days. Good drainage between boards, clean gaps and a ledger that is properly flashed keep that water from rotting the frame.
Average summer highs reach about 83°F, and around 17 days a year top 90°F. On a deck with full afternoon sun, dark composite can get uncomfortable on those days, so test samples in the sun before choosing a color.
Which decking material makes the most sense in Westmont?
For most Westmont homes, capped composite is the strongest starting point because about 98 freeze-thaw days a year are hard on unsealed wood and roughly 42.3 inches of snow a year means regular shoveling.
Budget, upkeep tolerance and sun exposure on your particular lot still decide the final choice between these options.
| Material | How it handles Westmont's conditions |
|---|---|
| Pressure-treated pine | Economical; needs sealing to resist freeze-thaw splitting |
| Cedar | Attractive and stable; refinish to keep its color |
| Capped composite | Low maintenance; handles moisture and freeze-thaw well |
| PVC | Lightest and most moisture-proof; premium price |
What kinds of homes are in Westmont, and how does that shape deck design?
Westmont has about 11,426 housing units across its covered ZIP code. 45% are single-family detached homes, 8% are attached homes such as townhouses and rowhouses, and about 47% are in buildings with two or more units. Roughly 59% of occupied homes are owner-occupied.
Because so much of the housing in Westmont is multi-unit, a meaningful number of decks and balconies are governed by condominium or building associations. For single-family homes and townhouses here, check whether any association rules apply before you design.
What deck projects are most common in Westmont?
Based on the age of Westmont's housing, the largest group of projects is likely to be replacing or rebuilding aging decks.
- Replacement and major repair: about 5,851 homes (51%) were built between 1970 and 1999, the age group whose original or early add-on decks are most likely to have worn-out framing, connectors and boards.
- Retrofit decks on older homes: about 4,019 homes (35%) predate 1970. Here the priority is confirming that add-on decks are properly attached — or rebuilding them freestanding — before any cosmetic work.
- Upgrades and expansions: about 392 homes (3%) were built since 2010. Their decks are usually sound but small or builder-grade, so enlarging the deck, adding stairs and switching to composite or upgraded railings are common.
When is the best time to plan a deck project in Westmont?
With about 144 freezing days a year, the building window in Westmont is compressed. Design, drawings and permits are usually handled in winter so footings can go in as soon as the ground allows in spring, and finishes like stain are applied before nights turn cold in fall.
Do you need a permit to build a deck in Westmont?
Often, yes — especially for attached or elevated decks — but the rules are set locally. Check with the building department that serves your address: the municipality, or DuPage County for unincorporated areas.
For Westmont, IL, ask the permit office whether your deck needs a permit based on its size, height and attachment to the house, which drawings and inspections are required. Statewide code background for Illinois is on our state page; local rules change, so the building department remains the authority.
How does Westmont compare with nearby covered areas?
The closest covered area is Clarendon Hills, about 0.6 miles from the center of Westmont's covered ZIPs. Its median home was built in 1977, 1 years later than in Westmont. Westmont has 21 percentage points fewer detached single-family homes (45% vs. 66%), which changes how many projects are backyard decks versus compact townhouse decks. Owner-occupancy is 59% in Westmont compared with 78% in Clarendon Hills. Westmont's covered ZIP code span about 4.7 square miles of land with roughly 11,426 homes — about 2,431 per square mile, a typical suburban density where most homes have usable backyards.
| Area | Distance | Median year built | Covered ZIPs |
|---|---|---|---|
| Clarendon Hills | 0.6 mi | 1977 | 1 |
| Hinsdale | 2.3 mi | 1981 | 1 |
| Downers Grove | 2.4 mi | 1974 | 2 |
| Oak Brook | 3.1 mi | 1977 | 1 |
| Darien | 3.4 mi | 1978 | 1 |
| Western Springs | 3.8 mi | 1961 | 1 |
Deck planning checklist for Westmont homeowners
- Confirm your ZIP code is 60559, the covered Westmont ZIP.
- Find out when your current deck was built and whether it uses pre-2004 treated lumber.
- Ask what footing depth your building department requires for frost.
- Plan stair location and snow storage so winter shoveling doesn't damage boards or railings.
- Probe the ledger, post bases and joist tops for soft wood before planning a resurface.
- Call 811 before any digging so utility lines are marked.

