City of Charleston bans “slab-on-grade” construction in floodplain

Ordinance prevents worsening flooding in vulnerable locations

CHARLESTON, S.C. — Yesterday, Charleston City Council unanimously passed an ordinance banning “slab-on-grade” foundations after years of partnership with the Coastal Conservation League, Historic Charleston Foundation, and the Southern Environmental Law Center and with support from other local stakeholder groups including the Charleston Trident Association of Realtors, Charleston Homebuilders Association, and Charleston Metro Chamber of Commerce. The commonsense ordinance, an important recommendation of the Dutch Dialogues Charleston, will stop slab-on-grade construction, also known as “fill-and-build,” in the 100-year floodplain where houses have a greater chance of flooding each year, preventing the worsening flooding created by the practice.

A common building method in Charleston, “slab-on-grade” refers to the practice of piling dirt, pouring concrete for the foundation, and constructing the home directly on the concrete slab. While somewhat cheaper on the front end than other construction methods, the practice involves clear-cutting trees and changing a site’s elevation, which pushes flooding to neighboring areas and disturbs the ecosystem. And with sea levels rising and storms intensifying from climate change, homes in the floodplain will be at greater risk and need increased protections.

“Passing this ordinance signals council’s ongoing commitment to addressing patterns and risks associated with sea level rise and development related flooding issues,” said Betsy LaForce, Program Director for Sustainable Communities at the Coastal Conservation League. “This is a strong start to address the worsening flooding and storms we’re seeing each year.”

As Charleston rapidly grows, new developments using slab-on-grade construction exacerbate growing flood risk associated with sea level rise and intensifying storms. Slab-on-grade construction is also difficult to move or alter, which means that it creates expensive barriers to adapting to increasing flooding threats and other changing conditions.

“This is a step in the right direction to better protect the Charleston community,” said Cashion Drolet, Chief Advocacy Officer at the Historic Charleston Foundation. “We look forward to seeing what other ways we can work with the city to address worsening flooding.”

This historic move could serve as an example for other municipalities to empower and strengthen communities as threats from climate change become more urgent. As neighborhoods along the Southern coast face rising sea levels and stronger storms, the need for policies that require resilient development practices grows.

“We can’t stop Charleston from flooding, but we can stop construction practices that make it significantly worse,” said Chris DeScherer, Director of SELC’s Charleston office. “The collaboration that led to this commonsense ban on slab-on-grade construction in the floodplain is what’s needed not only to build Charleston’s resilience to climate change, but it can also serve as a roadmap for other cities hoping to tackle the problem of worsening flooding.”