Almost everyone arrives in Gettysburg for the same three days in July 1863. The borough that grew up around them is small: 1.7 square miles, about 7,100 people, hemmed in on three sides by the national military park.
The place under that name is not one place. Cumberland Township surrounds the borough on three sides and holds almost exactly the same number of people, roughly 7,000, across 33.6 square miles. Straban Township closes the eastern side. So a great many people with a Gettysburg mailing address do not live in the borough at all, and their house is nothing like the ones in the historic district. Keep going and you reach the boroughs, Littlestown and New Oxford and Fairfield and Biglerville and Carroll Valley, then the orchards along the foot of South Mountain, then farmland and the stone farmhouses standing in it.
Water does not care about any of that, but the building does. A pre-1900 stone-and-mortar foundation in the borough was built to breathe, and sealing it with modern impermeable materials traps moisture inside the wall. A 1990s slab or crawl space out in Straban is a completely different repair. Lake Heritage, two miles south-east of the square, is 2,150 people living around a 154-acre lake, where a high water table is simply a fact of the address. A quote that prices those the same was written without looking at the house.
One more thing worth knowing before you call anyone. Pennsylvania does not license or certify mold remediation, and the state contractor register lists 564 active home improvement registrations across Adams County without a single one carrying the word mold in its business name. Every place below has its own page.