Deck builders in Cook County, IL

Cook County has about 2,276,493 homes, with a median construction year of 1961 (the Illinois median is 1971). Within our covered ZIP codes — about 610,210 homes — the median is 1967, 6 years newer than the county overall.

The median home in the covered parts of Cook County dates to about 1967, roughly 59 years ago. Most homes from that era were built without a deck; the decks you see now were usually added in later decades, sometimes by previous owners with little documentation.

That history matters: retrofit decks are where missing ledger flashing, undersized footings and nailed-rather-than-bolted connections are most common. Before resurfacing or extending an add-on deck, it is worth confirming how it was framed and attached.

Oldest housing: Oak Park (1934), Berwyn (1938) and Kenilworth (1938). In these communities, expect retrofit decks on older houses and aging decks that need structural inspection, ledger and flashing upgrades, or replacement. Newest housing: Lemont (1992), Barrington (1982) and Streamwood (1981). Here, projects lean toward enlarging builder-installed decks, adding stairs and railings, and upgrading to low-maintenance boards.

The nearest NOAA climate station with 1991–2020 normals is Chicago Ohare Intl. AP, about 2 miles away. It records an average of 121 days a year with a low at or below 32°F — a substantial freezing season. On roughly 78 of those days the temperature climbs back above freezing, so water in wood, soil and gaps between boards repeatedly freezes and thaws.

For Cook County, 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.

Average snowfall near Cook County is about 33.6 inches a year (Chicago Botanic Garden). That's enough that shoveling and ice-melt choices affect deck surfaces, and stair treads benefit from good texture and drainage.

Precipitation averages about 39.5 inches a year, falling on about 74 days with 0.1 inch or more — wet enough that drainage and flashing still matter, but dry spells also let wood surfaces dry out and check in the sun.

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.

• Retrofit decks on older homes: about 1,391,029 homes (61%) predate 1970. Here the priority is confirming that add-on decks are properly attached — or rebuilding them freestanding — before any cosmetic work.
• Replacement and major repair: about 589,699 homes (26%) 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.
• Upgrades and expansions: about 114,864 homes (5%) 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.

40% of Cook County's homes are detached single-family houses and 5% are townhouses or other attached homes; 58% of occupied homes are owner-occupied. With mostly detached homes, wood remains a practical lower-cost option for homeowners willing to clean and seal on schedule.

Illinois building codes for single-family homes are largely adopted and enforced at the municipal and county level, so requirements differ between suburbs. Contact your village or city building department. Before work starts, confirm with the building department for your exact address whether a permit is required, what drawings and inspections it involves, and whether an HOA must approve the design.