Gettysburg Homes by the Numbers: House Age, Rain and Where Moisture Starts

By John Calhoun, owner of Mold Remediation Gettysburg PA · Data pulled October 20, 2026

I'm John Calhoun. I run Mold Remediation Gettysburg PA, and I like numbers that come from somewhere. Every figure on this page is public: the U.S. Census Bureau's American Community Survey for the houses, NOAA's climate normals for the weather, and FEMA's records for floods. I pulled them so you can see what kind of house you're likely dealing with before anybody shows up with a moisture meter. The tables are below, and the parts of town each have their own page.

How old are the houses around Gettysburg?

The borough and the townships are two different housing stories. Inside the borough, nearly half the homes predate 1940 and close to 8 in 10 predate 1970. Out in Cumberland, Straban or Mount Joy Township, the median house is from around 1980.

Lake Heritage is a Census-designated place that sits across parts of Straban, Mount Joy and Mount Pleasant townships, so its homes are also counted in those townships.

Inside the borough: the north end and the rest of town

The Census splits the borough into exactly two tracts. Tract 315.01 is the north end, including Gettysburg College. Tract 315.02 is Lincoln Square and everything south, west and east of it: downtown, Baltimore Street, Steinwehr Avenue, the Seminary Ridge side and the east side toward Rock Creek. They're more alike than you might guess.

Both halves of town are about half pre-1940 housing and about half rented. The south tract has more of the 1940s through 1970s infill: 90% of its homes were built before 1980, against 76% in the north end.

Why a house's age changes where the water gets in

Mold needs moisture. The EPA puts it plainly: the key to mold control is moisture control. A house's age doesn't make mold, but it does change the usual ways water finds its way inside.

Older houses, the kind that fill the borough, were built before vapor barriers, foundation drainage and bathroom exhaust fans were standard. Water tends to come through the foundation walls, around old windows and chimneys, and through decades of roof patches. These houses also breathe, which helps them dry, until someone finishes the basement or closes them up tight.

Newer houses, common in the townships, are tighter. They keep outside water out better, but the moisture made inside (showers, cooking, a dryer, a damp crawl space) has fewer places to go. Those homes more often show condensation, plumbing leaks hidden behind finished drywall, and trouble in finished basements and crawl spaces.

Either way, the first job is the same: find the water. The rest of this site explains how, starting with moisture mapping.

Renters, rowhouses and shared walls

The second big difference is who lives in the house and how many households share the building.

More than half of borough households rent, and about 1 in 6 borough homes is an attached single-family house, a rowhouse or a twin. That means a leak doesn't always stay in the unit where it starts. Water from an upstairs bathroom shows up on a downstairs ceiling, and a damp party wall belongs to two owners. Cumberland and Straban have a different wrinkle: mobile homes make up roughly 1 in 11 and 1 in 15 homes there, and those have their own moisture habits under the floor.

Rain every month: Gettysburg's climate normals

There's no dry season to wait out a wet basement. NOAA's 1991 to 2020 normals for the Eisenhower National Historic Site station, just outside town, show at least 2.7 inches of precipitation in every month and about 44.5 inches a year. June and September are the wettest months.

Two things in that table matter to a basement. Summer brings warm, wet air while the ground stays cool, so a basement wall can sweat even when no water is coming through it. And January lows near 21 °F are cold enough to freeze an exposed pipe, which is how a lot of winter leaks start. The station doesn't record humidity, so I won't quote a humidity number for Gettysburg.

How the houses are heated

Heating fuel says a lot about a house's mechanical room, and some of it matters for moisture.

Inside the borough, about two thirds of homes heat with utility gas and almost none with oil. Out in the townships it's a different mix: in Straban and Mount Joy roughly 1 in 5 homes burns fuel oil and another 1 in 5 uses propane, and nearly half of Lake Heritage heats with electricity. Two moisture notes come with that. Any heater that burns fuel without a vent to the outside, like a portable propane or kerosene heater, puts water vapor into the room along with heat, so it's worth knowing if a damp room has one. And a house with the heat shut off in winter is a house where pipes can freeze.

Empty and seasonal houses

About 1 in 8 homes in the borough was vacant when surveyed, roughly double the township rates, and the Census counts around 100 borough homes held for seasonal or occasional use. These are small-sample estimates (the seasonal count carries a margin of plus or minus 74), so take them as a rough picture. The point for mold is simple: an empty house is where a small leak runs longest before anyone sees it. Seasonal figures for Cumberland and Straban weren't available in this pull.

Flood history: what FEMA's records show

I won't tell you which streets flood, because I haven't seen a source that says so. What the public record does show is how often flood water has turned into insurance claims and disaster declarations around here.

Flood insurance claims. FEMA's National Flood Insurance Program data lists 400 flood claims in Adams County from 1978 through 2026, and 83 of them in the Gettysburg ZIP code, 17325. Two years stand out countywide: 2011, with 133 claims (an April storm and Tropical Storm Lee in September), and 1996, with 97 (a January thaw-and-rain flood and a June flood). FEMA labels four 17325 claims from September 2021 as Hurricane Ida. By my count of FEMA's claim records, the county's claims cluster in September, April and January. The 17325 ZIP code covers a lot of ground beyond the borough, so these counts are not a borough flood map.

Flood insurance in force. FEMA's policy data, as of September 2026, shows 91 active flood insurance policy records in ZIP 17325 and 27 in Gettysburg borough, which participates in the program as community 421243. Flood damage usually isn't covered by a homeowners policy, so that small number is worth noticing.

Stevens Run crosses the battlefield and runs through the borough in a concrete channel, partly covered, before it joins Rock Creek on the east side of town. The borough's floodplain ordinance adopts FEMA flood maps dated July 22, 2020. If you're near either creek, look up your own address on the FEMA Flood Map Service Center. More detail is on the page about homes near Stevens Run and Rock Creek.

Old paint: why the year your house was built matters for mold work

The EPA's Renovation, Repair and Painting rule applies to paid work that disturbs paint in homes built before 1978. Mold work often means cutting out drywall or plaster, so in an older house it can fall under that rule. The Census groups houses by decade, so the closest it gets is "built before 1980": that's 87.2% of homes in the borough and 49.5% across Adams County. If your house is that old, ask any contractor how they handle painted surfaces. The EPA's RRP page explains the rule.

The parts of the Gettysburg area, one page each

• Downtown Gettysburg and Old Town Lincoln Square and the four main streets: old buildings, apartments over shops, and the historic district rules.
• The college area and borough rentals Licensed rentals, turnover between tenants, and the vents and leaks the inspection checklist doesn't catch.
• Homes near Stevens Run and Rock Creek The creek in a concrete channel, the borough's wall project, and what to do after a big storm.
• Cumberland Township The township that wraps around the borough: much newer homes, townhouses, mobile homes and tighter houses.
• Straban Township Mostly owner-occupied single homes east of the borough, from homes built before 1940 to houses built since 2020.
• Lake Heritage A private lake community from the 1960s, nearly all owner-occupied, with homes mostly from the 1970s on.
• Borough vs. township: why your address matters Same mailing address, different houses and different rules. What changes when you cross the borough line.
• The ground under Gettysburg Shale, sandstone and diabase, a shallow water table, and why I measure instead of assuming.

For the bigger picture, there's the overview of mold remediation in Gettysburg, PA, my mold services, and the full set of mold and moisture guides.

About this data

Housing figures are U.S. Census Bureau American Community Survey 5-year estimates for 2020 to 2024 (tables B25034 Year Structure Built, B25035 Median Year Structure Built, B25003 Tenure, B25024 Units in Structure, B25040 House Heating Fuel, B25002 and B25004 Occupancy and Vacancy, and B25077 Median Value), pulled from data.census.gov on October 20, 2026. Borough tract figures are for Census Tracts 315.01 and 315.02, which together make up the borough exactly. They're survey estimates with margins of error. For the borough, the total of 2,801 homes carries a margin of about plus or minus 214, so treat small gaps between places as noise. Climate figures are NOAA 1991 to 2020 monthly normals for station USC00362537. Flood claim and policy counts come from FEMA's OpenFEMA NFIP datasets (claims through August 2026, policies as of September 8, 2026), and declarations from FEMA's disaster declarations summaries. Percentages are my arithmetic from the published counts.