How Impervious Surface Limits Can Affect Your Outdoor Living Project

There are many rules, building codes, and zoning ordinances that guide outdoor living projects in Raleigh, Durham, and the greater Triangle. Many property owners are familiar with the need to obtain a building permit and subsequent inspections for safety, but many do not know about the environmental regulation limiting impervious surface areas. If you’re planning to add to, renovate, or alter your property in any way, staying in compliance with impervious surface limits is an important consideration.

What is an impervious surface limit?

An impervious surface limit is the amount of surface area on your property that can be covered by a material that significantly reduces the natural drainage of water into the soil. Land covered by materials such as concrete, stone, wood, or asphalt – which are commonly used in driveways, sidewalks, patios, and decks – count as an impervious surface area.

Impervious limits are monitored by local Stormwater Management Offices and vary by locale. Regulating impervious surface areas is an environmental effort to promote a healthy drinking water supply. Rainwater that runs off of these surfaces can flow back into the drinking water supply without the benefit of filtration through the soil, and raise the risk of contaminating the local drinking water.

What if I exceed my impervious surface limit?

When preparing for a new outdoor living expansion, you will need to find out if you are currently complying with your impervious surface limits and, if so, how much room remains on which you can build. Homeowners who exceed their impervious surface limits will be responsible for removing materials in order to comply.

Archadeck can help you determine the impervious surface limits of your property. If you discover you have already exceeded or are at risk of reaching the limits, we may be able to find design solutions to achieve your project goals while staying within the limits. While this may mean some alterations in your project’s scope, it could be as simple as adding a special infiltration device, rain garden, or cistern to comply.

What is my impervious surface limit?

Impervious surface limits vary widely from county to county, city to city, town to town, and even from neighborhood to neighborhood. For example, the unincorporated parts of Wake County, outside of watershed areas, have a 30% impervious surface limit. The City of Raleigh has five zoning districts, each with a different impervious surface limit. You can look up your property through iMAPS to determine your specific impervious surface limit. These limits will be anywhere from 20%-65%. With such a broad range, it is vital for a homeowner to get the precise limit for their specific address from the local municipality.

What documentation is required to add impervious surfaces to my yard?

When adding on to your home, a survey or plot plan is required to be submitted to the building department as part of the permitting process to ensure you are staying within your impervious surface limits. The survey or plot plan should be completed by a licensed surveyor and indicated existing and proposed additions to your home. (If you do not already have a survey or plot plan, Archadeck can connect you with a licensed surveyor. Surveys can be used for any additional home improvements you may do in the future.) A stormwater tracking permit will then be issued for projects subject to the impervious surface limits.

When you work with Archadeck of Raleigh-Durham for your deck, patio, porch, or combination project, we will identify your impervious surface limit, submit a survey or plot plan, and obtain subsequent permits and inspections on your behalf. If impervious surface limits pose a challenge for your project, we have the experience and design capability to manage the limitations with creativity. If you’re ready to renovate an existing backyard space or add a new one, call today for a design consultation: 919-973-1523. We look forward to working with you!

Contact Us