How old are homes in McHenry County, and what does that mean for decks?
The median home in McHenry County was built in 1989; 18% predate 1960 and 26% were built since 2000.
McHenry County has about 121,329 homes, with a median construction year of 1989 (the Illinois median is 1971). Within our covered ZIP codes — about 12,113 homes — the median is 1993, 4 years newer than the county overall.
The median home in the covered parts of McHenry County was built around 1993. A deck built with a house of that age is now about 33 years old — the stage where first-generation pressure-treated decks commonly need major repair or replacement.
Decks built before 2004 were very likely made with CCA-treated lumber, which was phased out of most residential uses at the end of 2003. That doesn't make an existing deck unsafe, but old boards shouldn't be burned, and demolition debris should be disposed of according to local rules.
| Decade built | Homes | Share |
|---|---|---|
| 2020 or later | 1,349 | 1% |
| 2010s | 5,307 | 4% |
| 2000s | 24,407 | 20% |
| 1990s | 27,407 | 23% |
| 1980s | 16,290 | 13% |
| 1970s | 16,468 | 14% |
| 1960s | 7,857 | 6% |
| 1950s | 8,911 | 7% |
| 1940s | 3,655 | 3% |
| before 1940 | 9,678 | 8% |
How does McHenry County's climate affect deck building?
Covered parts of McHenry County average about 139 days a year at or below freezing (NOAA 1991–2020 normals).
The nearest NOAA climate station with 1991–2020 normals is Elgin, about 7 miles away. It records an average of 139 days a year with a low at or below 32°F — a substantial freezing season. On roughly 90 of those days the temperature climbs back above freezing, so water in wood, soil and gaps between boards repeatedly freezes and thaws.
For McHenry 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 McHenry County is about 32.1 inches a year (Elgin). That's enough that shoveling and ice-melt choices affect deck surfaces, and stair treads benefit from good texture and drainage.
Precipitation averages about 39.9 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 82°F, and around 15 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.
What deck projects are most common in McHenry County?
Based on the age of McHenry County's housing, the largest group of projects is likely to be replacing or rebuilding aging decks.
- Replacement and major repair: about 60,165 homes (50%) 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 30,101 homes (25%) 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 6,656 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.
Which McHenry County communities do you serve?
1 community in McHenry County have covered ZIP codes. Only the ZIPs listed are covered.
| Community | Covered ZIPs here | Median year built | Detached homes |
|---|---|---|---|
| Algonquin | 60102 | 1993 | 76% |
What decking material works best in McHenry County?
Capped composite is a strong default for McHenry County because about 90 freeze-thaw days a year are hard on unsealed wood and roughly 32.1 inches of snow a year means regular shoveling.
77% of McHenry County's homes are detached single-family houses and 10% are townhouses or other attached homes; 83% 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.
Who issues deck permits in McHenry County?
It depends on where you live: incorporated cities and towns in McHenry County usually run their own permit offices, while unincorporated areas are typically served by McHenry County.
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.