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Site Drainage White Papers

PC-SPL foundation drainage.jpg
The grade no longer slopes away from the building allowing water to pool around the foundation. Also note that the downspout does not directly connect to the underground drain pipe.

Maintaining good site drainage at historic properties needs to be approached carefully because of the individual complexities of a site. The interactions between roadways, buildings, vegetation, bodies of water, and the water table can become quite complicated. Addressing one problem may lead to another. Examples of this include:

  • Regrading to direct water away from a foundation may wash out the driveway.
  • Regrading a driveway could, in turn, direct water toward the building.
  • Any regrading on one property could cause issues on a neighboring property.
  • Downspout leaders, whether above grade or below grade, can cause erosion at the discharge point.
  • Visitor parking can compact the soil on a field creating an impervious surface. The soil becomes too dense to absorb the water, which then runs off into the next feature.

Additional complexities arise when managing cultural resources. Examples include:

  • Re-grading around a building foundation to create a better drainage solution may adversely affect a specimen historic tree or historic plantings.
  • Many historic structures were not designed to have gutters and it may be interpretively inappropriate to add them.
  • Excavation for drywells, trenches, and even regrading may require archaeological monitoring.
  • Overall manipulations of the site grading, such as the creation of swale to redirect water, may compromise the integrity of the historic landscape.

Basic Guidelines for Site Drainage:

  • Research and understand the existing components and aspects of the natural and man-made drainage. 
  • Monitor and maintain the existing systems.
  • Properly plan before implementing any project, taking in consideration the project’s relationship to the overall site drainage scheme and the integrity of the historic landscapes and structures.
  • Implement projects that achieve maximum results through the simplest means possible with the least impact to historic fabric, whether structural or landscape.
  • Document all changes made and components installed through labeled plans, drawings, and photography.

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Site Drainage White Papers