What the Age of Lake and Porter County Homes Tells Us About Their Chimneys
Census housing figures for both counties and fourteen of our towns, followed by a sweep’s reading of what each building era tends to leave on the roof.
By Mark Jason, owner of NWI Chimney Sweep · data from the U.S. Census Bureau; interpretation from 34 years on local roofs
What this study is, and is not
This page is a data study, not an account of a customer or a job. The numbers are public estimates from the U.S. Census Bureau, American Community Survey 2020-2024 5-year estimates, tables B25034 (Year Structure Built), B25035 (Median Year Structure Built) and B25040 (House Heating Fuel), retrieved through Census Reporter in October 2026. The Census Bureau does not count chimneys or fireplaces. Everything said here about chimneys is Mark Jason’s trade interpretation and is labelled as such.
How old are homes in Lake County and Porter County?
Lake County has 217,436 housing units and Porter County has 72,662, and Lake County’s stock is markedly older, per Census table B25034.
| Year structure built | Lake County units | Lake share | Porter County units | Porter share |
|---|---|---|---|---|
| 1939 or earlier | 31,748 | 14.6% | 5,928 | 8.2% |
| 1940 to 1959 | 53,489 | 24.6% | 7,703 | 10.6% |
| 1960 to 1979 | 58,185 | 26.8% | 20,914 | 28.8% |
| 1980 to 1999 | 34,712 | 16.0% | 20,244 | 27.9% |
| 2000 or later | 39,302 | 18.1% | 17,873 | 24.6% |
| All housing units | 217,436 | 100% | 72,662 | 100% |
The single largest decade in Lake County is the 1950s, with 33,515 units; in Porter County it is the 1970s, with 12,917. That twenty-year gap follows the way the region grew: the steel towns along the lake filled in first, and building moved south and east afterward. These are survey estimates and carry a margin of error, which is small for a county and larger for a small town.
Which Northwest Indiana towns have the oldest and newest homes?
Among the towns we serve, Lake Station has the oldest median home, built in 1965, and Winfield the newest, built in 2005, per Census table B25035.
| Town | Median year built | Built before 1960 | Built 1960 to 1979 | Built 2000 or later |
|---|---|---|---|---|
| Lake Station | 1965 | 42.6% | 25.6% | 8.5% |
| Highland | 1967 | 34.9% | 38.0% | 11.9% |
| Hobart | 1971 | 36.0% | 29.4% | 17.5% |
| South Haven | 1972 | 7.1% | 73.4% | 10.2% |
| Munster | 1973 | 26.1% | 42.4% | 14.8% |
| Merrillville | 1979 | 17.2% | 34.9% | 24.1% |
| Valparaiso | 1980 | 24.3% | 25.3% | 21.5% |
| Portage | 1981 | 17.2% | 31.5% | 22.7% |
| Lakes of the Four Seasons | 1982 | 4.2% | 40.0% | 4.7% |
| Schererville | 1989 | 8.6% | 24.0% | 26.6% |
| Crown Point | 1993 | 17.2% | 23.9% | 42.0% |
| Cedar Lake | 1997 | 24.5% | 11.1% | 46.1% |
| St. John | 2003 | 5.2% | 16.6% | 57.5% |
| Winfield | 2005 | 5.9% | 9.5% | 68.9% |
Fourteen of our sixteen towns appear here. Brunswick and Ross are not published as separate places in these tables, so we have no figures for them and will not estimate any. Read the percentages for the smallest places, South Haven, Winfield and Lakes of the Four Seasons, as approximate; their samples are small.
Three patterns stand out. Highland and Lake Station are mid-century towns, with roughly a third or more of their homes built before 1960. South Haven was built largely in the 1960s and 1970s, and Lakes of the Four Seasons mostly from the 1970s through the 1990s. St. John and Winfield are mostly twenty-first-century construction.
What do Lake and Porter County homes heat with?
Utility gas is the main heating fuel in about 86.3% of occupied homes in Lake County and 87.1% in Porter County, per Census table B25040.
| Main heating fuel | Lake County homes | Lake share | Porter County homes | Porter share |
|---|---|---|---|---|
| Utility (piped natural) gas | 168,414 | 86.3% | 59,797 | 87.1% |
| Electricity | 20,524 | 10.5% | 7,057 | 10.3% |
| Bottled or tank gas (propane) | 3,849 | 2.0% | 987 | 1.4% |
| Wood | 426 | 0.2% | 245 | 0.4% |
| Fuel oil or kerosene | 437 | 0.2% | 105 | 0.2% |
Only 426 Lake County households and 245 Porter County households report wood as their main heating fuel. That does not measure fireplaces. The survey asks for the fuel used most, so a home with a gas furnace and a wood-burning fireplace is counted under gas. What the table does show is that nearly every home here has a gas appliance that vents somewhere, and in an older house that somewhere is frequently the masonry chimney.
What each building era usually means for a chimney
In our experience the decade a Northwest Indiana house was built predicts its chimney type and its most likely fault better than any other single fact.
This section is trade interpretation, not Census data. It describes tendencies Mark has seen over 34 years. Individual houses differ, and only an inspection tells you what a particular flue is.
| Era built | Typical chimney (Mark’s observation) | What tends to go wrong | First thing to check |
|---|---|---|---|
| 1939 or earlier | Brick stack, sometimes with no liner at all, soft lime-based mortar, flues sized for coal | Eroded joints inside the flue; gas water heater venting into a flue far too large for it | Whether a liner exists and its condition |
| 1940 to 1959 | Clay-tile-lined masonry, often two flues (fireplace and furnace), flat mortar crown | Cracked crown, open tile joints, no cap | Crown, cap and a camera pass of each flue |
| 1960 to 1979 | Wide exterior chimney on a brick ranch or split-level; wood stoves and inserts added in the 1970s | Glazed creosote from inserts vented into unlined fireplace flues; weak flashing on low roofs | How any insert is connected, and the flashing line |
| 1980 to 1999 | Factory-built (prefab) fireplace with a metal chimney inside a framed, sided chase | Rusted chase cover leaking into the chase; worn refractory panels; wrong replacement parts | Chase cover and the firebox data plate |
| 2000 or later | Direct-vent gas fireplace; high-efficiency furnace vented by plastic pipe through a wall | Pilot and sensor wear, fogged glass, blocked vent terminals; sometimes no chimney at all | Service history of the gas unit |
Put the two halves together. By the Census figures, 39.2% of Lake County housing units date from before 1960. In our reading, that is the stock most likely to have a clay-tile or unlined flue serving a gas appliance it was never sized for, which is why relining with a correctly sized stainless liner comes up so often in the older northern towns. In St. John and Winfield, where most homes were built after 2000, the common call is a gas fireplace tune-up instead.
How to use this study for your own house
Find your home’s build year, match it to the era table above, and treat the listed fault as the first thing to rule out.
Your county assessor’s record or closing papers give the year. If the house has changed fuel or appliance since it was built, for example a furnace replaced by a high-efficiency unit, or gas logs set in a wood fireplace, the original flue is now doing a job it was not sized for. NFPA 211, the standard we work to, calls for a Level 2 inspection when an appliance or fuel changes and when a property is sold.
Next steps by era: owners of pre-1960 homes should start with a chimney inspection with a camera scan; owners of mid-century masonry chimneys showing stains or loose mortar should read about chimney repair and masonry work and caps and crown repair; and anyone unsure what a sign means can use the chimney symptom checker. Starting prices for all of it are on the pricing page.
Questions about the data
What year were most houses in Lake County, Indiana built?
The median housing unit in Lake County, Indiana was built in 1968, according to the U.S. Census Bureau, American Community Survey 2020-2024 5-year estimates, table B25035. The busiest single decade was the 1950s, and about 39.2% of the county’s units were built before 1960, which makes its housing noticeably older than neighbouring Porter County’s.
Are homes in Porter County newer than homes in Lake County?
Yes. The median Porter County home was built in 1982, compared with 1968 in Lake County, per the U.S. Census Bureau, American Community Survey 2020-2024 5-year estimates. Porter County’s largest building decade was the 1970s, and about 24.6% of its housing units date from 2000 or later, against 18.1% in Lake County.
Is this chimney case study based on a real customer?
No. This page is a data study built from public U.S. Census Bureau housing estimates for Lake and Porter County, not a description of any customer, address or job. The commentary on what each housing era means for chimneys is the trade opinion of Mark Jason, the owner of NWI Chimney Sweep, and is labelled that way throughout.
Does the Census count how many homes have a fireplace or chimney?
No. The American Community Survey records when a structure was built and which fuel heats it most, but it does not ask about fireplaces or chimneys. A home with a gas furnace and a wood fireplace is counted under utility gas. That is why this study uses building age as an indirect guide and says plainly where interpretation begins.
Do houses built before 1940 have chimney liners?
Some do not. Many chimneys built before 1940 were laid as bare brick with no clay tile liner, and others have early tile that has since deteriorated. That is Mark’s field observation, not a Census figure. The only way to know for a given house is a camera inspection of the flue from top to bottom.
What kind of fireplace do 1980s and 1990s houses usually have?
Homes from the 1980s and 1990s in Northwest Indiana commonly have a factory-built, or prefab, fireplace: a metal firebox and metal chimney enclosed in a framed chase finished with siding. The usual weak point is the sheet-metal chase cover on top, which rusts through and leaks. This is trade observation, not survey data.
Why does it matter that most Northwest Indiana homes heat with gas?
It matters because gas exhaust is cool and carries a lot of water vapor. About 86.3% of occupied Lake County homes heat mainly with utility gas, per Census table B25040, and in older houses that exhaust often rises through a masonry flue built for a hotter, larger appliance, where it condenses and slowly attacks the mortar and tile.
Why are Brunswick and Ross missing from the town table?
Brunswick and Ross are not published as separate places in the Census tables this study uses, so there are no year-built figures to report for them. We serve both communities, but we left them out of the table instead of estimating numbers we cannot source.
Know your home’s build year? That is a good start.
Call and tell us the decade and what is connected to the chimney. We will tell you what to have checked first.
Call (219) 203-9797