Of Conshohocken’s 4,847 housing units, 1,738, or 36%, are in buildings put up in 1939 or earlier, according to the Census Bureau’s American Community Survey estimates for 2020 through 2024. In West Conshohocken the share is 46%, or 353 of 765 units. Across Montgomery County it is 16%. Conshohocken also has a large group of new housing: 36% of its units were built in 2000 or later.
What the survey measures
The American Community Survey (ACS) is the Census Bureau’s continuing survey of a sample of households. The 5-year estimates pool five years of responses, which lets the Bureau publish figures for places as small as these two boroughs. The survey counts housing units, so each apartment, rowhouse or single house counts once, whether it is occupied or vacant.
Every figure comes with a margin of error, the range around the estimate that the Census Bureau gives a 90% chance of containing the true number. For small boroughs the margins are wide. Conshohocken’s count of units built in 1939 or earlier is 1,738, plus or minus 294. West Conshohocken’s is 353, plus or minus 93.
Year built
| Year built | Conshohocken | West Conshohocken | Montgomery County |
|---|---|---|---|
| 2020 or later | 2.8% | 0.1% | 1.5% |
| 2010 to 2019 | 19.1% | 8.5% | 6.6% |
| 2000 to 2009 | 13.8% | 14.5% | 8.6% |
| 1990 to 1999 | 2.7% | 12.5% | 10.8% |
| 1980 to 1989 | 3.2% | 1.6% | 11.4% |
| 1970 to 1979 | 6.5% | 1.6% | 12.1% |
| 1960 to 1969 | 3.3% | 6.1% | 11.7% |
| 1950 to 1959 | 7.2% | 4.7% | 15.9% |
| 1940 to 1949 | 5.7% | 4.2% | 5.4% |
| 1939 or earlier | 35.9% | 46.1% | 16.0% |
The median year built, the year that splits each area’s housing units in half, is 1971 for Montgomery County. It is 1964 for Conshohocken, plus or minus 14 years, and 1949 for West Conshohocken, plus or minus 17 years.
Conshohocken’s stock comes in two large groups. The units from 1939 or earlier make up 35.9% of the total, and the units from 2000 or later make up 35.7%. The decades in between account for less than a third. Recent permits add to the newer group. In the Census Bureau’s Building Permits Survey for 2025, Conshohocken issued permits for three single-family houses and one building with 168 units, and West Conshohocken issued a permit for one single-family house.
Kinds of buildings
| Units in building | Conshohocken | West Conshohocken |
|---|---|---|
| 1, detached | 12.0% | 39.9% |
| 1, attached | 43.7% | 53.6% |
| 2 | 4.1% | 4.1% |
| 3 or 4 | 6.5% | 2.1% |
| 5 to 9 | 4.9% | 0.0% |
| 10 to 19 | 2.3% | 0.4% |
| 20 to 49 | 2.3% | 0.0% |
| 50 or more | 24.3% | 0.0% |
The Census Bureau’s “1, attached” category covers single-family houses that share a wall with a neighbor, such as twins and rowhouses. They are the largest group in both boroughs: 2,117 of Conshohocken’s units, or 43.7%, and 410 of West Conshohocken’s, or 53.6%. Detached houses make up 12.0% of Conshohocken’s units and 39.9% of West Conshohocken’s. Conshohocken has 1,176 units in buildings with 50 or more apartments, 24.3% of its total. The estimate for West Conshohocken in that category is zero.
What a house’s age says about its roof
The year a house was built is the oldest its roof could be. On InterNACHI’s estimates of 20 years for 3-tab asphalt shingles and 30 years for architectural shingles, an asphalt roof on a house from before 1940 is unlikely to be the first one the house has had.
Slate roofs last longer. The National Park Service’s slate roof brief gives Pennsylvania soft-vein slate more than 60 years and Pennsylvania hard-vein slate roughly 100. A slate roof put on in the 1920s or 1930s can be near the end of those ranges. For a roof of that age, the brief suggests weighing its age and condition against the expected life of the slate it is made of. The guide to roofing materials lists the estimates for each type.
Attached houses bring a rule of their own at the borough level. Conshohocken’s re-roofing addendum says that where roof surfaces next to a wall are at the same elevation, approved fire-retardant-treated wood must be used for 4 feet on each side. Ask the borough’s Licenses and Inspections office how it applies to a particular roof.
Finding the age of a particular roof
Conshohocken requires a building permit and a re-roofing addendum to replace a roof, so the borough may have a record of earlier re-roofing work at an address. The borough posts a Right to Know request form on its applications and forms page for requesting public records.
A home inspection will not settle the question. InterNACHI’s standards of practice say an inspector is not required to determine the age of a component or to predict how long it will last. The roof inspection checklist covers what an inspection does include.
Limits of these figures
The margins of error are large enough that small categories, such as Conshohocken’s 137 units built in 2020 or later (plus or minus 103), say little on their own. The survey also counts housing units, not roofs. Conshohocken’s 1,176 units in buildings of 50 or more apartments sit under far fewer roofs than its 2,117 attached houses, so counts by unit give large buildings more weight than their share of the borough’s roofs.