Highland Township sits west of the borough along Fairfield Road, Knoxlyn Road, and Marsh Creek. It is a quiet, rural township with homes spread across farmland and wooded lots. West of Gettysburg off Fairfield Road, about 10 minutes from our office.
Homes on low ground near Marsh Creek and its branches can see high groundwater in wet seasons. Basements and crawl spaces there take on moisture from below, even when there is no visible leak.
Wooded lots keep houses shaded, so roofs, siding, and the soil around foundations dry out slowly after rain.
Quick answer
Highland Township has about 413 homes, and 53.0% were built before 1980 (49.5% across Adams County). FEMA records 84 flood insurance claims in ZIP 17325, most in 1996. Published national benchmarks put a typical mold remediation project at $1,223-$3,757 (Angi) to $1,500-$6,000 (HomeGuide); a written quote after inspection sets the real price, and the first step is always finding the water.How costs break down.
How old the homes are, how many share walls, and how often water has come in, compared with Adams County and Pennsylvania.
| Measure | Highland Township | Adams County | PA |
|---|---|---|---|
| Population | 852 | 106,115 | 13,018,639 |
| Housing units | 413 | 43,672 | 5,806,452 |
| Median year built | 1979 | 1980 | 1965 |
| Built before 1940 | 18.9% | 17.5% | 25.0% |
| Built before 1960 | 29.3% | 29.4% | 44.9% |
| Built before 1980 | 53.0% | 49.5% | 67.2% |
| Built 2000 or later | 29.5% | 22.3% | 14.3% |
| Single-family detached | 92.0% | 74.7% | 56.6% |
| Attached homes (rowhouse, twin, townhouse) | 2.7% | 9.3% | 18.8% |
| Mobile homes | 3.4% | 5.5% | 3.5% |
| Owner-occupied | 88.5% | 78.9% | 69.3% |
| Median home value | $359,100 | $268,500 | $254,500 |
Sources: U.S. Census Bureau, American Community Survey 2020-2024 5-year estimates, tables B01003, B25001, B25003, B25024, B25034, B25035 and B25077 (profile); FEMA OpenFEMA NFIP redacted claims, data as of 2026-09-08. Municipal claims use FEMA's NFIP community; ZIP claims use the reported ZIP code, which can cross municipal lines. ACS figures are survey estimates with margins of error, and small places have wider margins. Paid amounts are not adjusted for inflation.
That chalky residue is efflorescence, salt left behind when groundwater moves through concrete or block and evaporates. It is not mold, but it proves water is passing through the wall.
Fiberglass batts between the joists that droop or fall out have usually absorbed moisture. Wet insulation holds water against the subfloor and hides growth behind it.
Boards that curl up at the edges over a crawl space are taking on moisture from below. The same damp air is reaching the joists and sill plate.
Corroded fasteners and joist hangers in the crawl space mean the air down there stays humid for long stretches, which is exactly what mold needs.
An odor that shows up a day or two after heavy rain and fades in dry weather points to a rising water table rather than a plumbing leak.
Groundwater does not stay at one depth. After a wet spell, the water table under creek-side lots can rise close to the bottom of a foundation, and concrete is porous enough to wick that moisture upward. Even without puddles on the floor, a slab or block wall in contact with wet soil keeps releasing water vapor into the basement or crawl space, raising the relative humidity well past the 60% ceiling the EPA recommends.
Vented crawl spaces add a second problem in summer. Warm, humid outdoor air flows in through the vents and meets joists and ductwork that are cooled by the soil. When those surfaces fall below the dew point of the incoming air, moisture condenses right on the wood. That is why many crawl spaces are wettest in July, not in spring. Tree cover makes it harder to recover. Shade keeps the soil around the foundation cool and wet, and leaf litter in gutters sends roof water straight down beside the wall instead of away from it.
Highland Township homes on low ground near Marsh Creek take on moisture from below, and wooded lots keep it from drying. Most of the work is in crawl spaces and basements.
Cleaning joists and adding moisture control in damp crawl spaces.
Crawl spaces on damp ground stay humid all summer. We clean the joists and subfloor, cover the soil with a sealed vapor barrier, and look at whether a crawl space dehumidifier is needed to keep it dry.
Basements that take on groundwater, with a humidity plan afterward.
Basements that take on groundwater in wet months need more than cleaning. After removing mold, we set up a dehumidifier sized for the space and check whether drainage outside could reduce the water coming in.
Finding whether the moisture is coming from below, outside, or inside.
An inspection separates the three usual sources: water coming up from below, water coming in from outside, and humidity from inside the house. Each one has a different fix.
Every service we offer is available in Highland Township.
We take moisture meter readings on the slab, the lower block courses, and the sill plate, and compare them with readings higher up. A pattern that is wettest at the bottom confirms groundwater is the driver.
Crawl space and basement work is set up under containment with negative air pressure so spores do not travel up into the living space. Joists and subfloor are HEPA vacuumed and cleaned, and wet insulation is bagged and removed.
Drying continues until the wood reaches normal moisture content, not just until it feels dry. We confirm with meter readings before anything is covered back up.
A sealed vapor barrier over the crawl space soil and a dehumidifier set around 50% keep the space from climbing back up after the next wet season. We also point out gutters and grading that are sending water to the foundation.
We look at where the house sits relative to the creek and the slope of the lot. On shaded lots, we also check siding and roof edges that stay wet under tree cover.
Homes out here are spread apart, so we group visits where we can and schedule drying checks ahead.
Sometimes. A properly sized dehumidifier set to 50% can keep a basement dry if the water is coming in as vapor. If water is seeping in as liquid, the outside drainage has to be fixed as well, or the dehumidifier just runs all the time.
Yes, all of Highland Township is in our area. Call and we will schedule an on-site visit.
Closing the vents alone usually does not help, because the soil still releases moisture into a sealed space with nowhere to go. Vents should be closed only as part of a plan that includes a vapor barrier over the soil and some form of dehumidification. Done that way, a closed crawl space typically stays drier than a vented one.
Usually not. White, crystalline powder that crumbles when you touch it is efflorescence, which is mineral salt. Mold tends to be fuzzy or spotted and often grows on organic material nearby, like wood or cardboard. Efflorescence is still a sign of moisture, so it is worth finding out where the water is coming from.
Yes. Warm air rises and leaves through the upper floors, and air from the crawl space moves up to replace it through gaps around pipes, wires and ducts. That is called the stack effect, and it is why a crawl space problem can show up as a musty smell in the bedrooms.
More answers on our mold FAQ page.
Call and tell us whether the moisture shows up after rain or all the time. That tells us whether to look at groundwater or humidity first.
