Why Charleston Banned Slab-on-Grade Foundations

concrete slab foundation in early stages of construction

On April 11, 2023, Charleston City Council unanimously voted to prohibit slab-on-grade foundations for residential single-family homes, duplexes, and townhouses within the 100-year floodplain. The ordinance became effective January 1, 2024.

Why did Charleston officials deem this measure necessary, and what does it mean for residents? We’ll explain more, but let’s first discuss slab-on-grade foundations.

What is a Slab-on-Grade Foundation?

A slab-on-grade foundation is a concrete slab foundation poured directly on the ground. It serves as a base for houses, garages, commercial buildings, and other structures. They are constructed by digging a shallow trench, adding gravel for drainage, and pouring concrete to create a solid and stable slab. This method is relatively affordable and efficient, and its direct contact with the ground can help regulate temperatures, potentially improving energy efficiency compared to other foundation types. However, slab-on-grade foundations may be cost-effective and common in Charleston, but they pose challenges in this flood-prone coastal area. The region’s low elevation and flat topography make homes built on slab-on-grade foundations particularly susceptible to flooding.

Why Did Charleston Ban Slab-on-Grade Foundations?

The Charleston slab-on-grade ban intends to mitigate flood risks and promote sustainable building practices in the Charleston, SC, region. Several factors led to this unanimous decision, including:

1. Flooding

The construction of a concrete slab foundation often requires elevating the building site with fill dirt, which can disrupt natural water drainage patterns. This can increase water runoff, causing displacement onto nearby properties, which worsens flooding within the community. Banning slab-on-grade foundations prevents this drainage disruption, especially during extreme weather conditions.

2. Environmental Impact

Slab-on-grade foundation sites typically involve clear-cutting vegetation and modifying land elevation. These actions disturb surrounding ecosystems and reduce the natural absorption and management of stormwater.

3. Climate Change

Future climate predictions indicate rising sea levels and more frequent severe weather, which increases Charleston’s susceptibility to flooding. Slab-on-grade foundations are less adaptable to these changes, making other foundation types more viable.

How Charleston’s Slab-on-Grade Ban Impacts Homeowners

Banning slab-on-grade foundations benefits the Charleston community in several ways, as alternative foundation types, such as pier and beam and crawl spaces, become necessary. These alternatives offer longer-term benefits by reducing potential flood risk and enhancing the structure’s durability. While pier and beam, and crawl space foundations better align with sustainable building practices, the initial construction cost may be higher.

Remember, new building permit applications for residential structures within the 100-year floodplain, submitted on or after January 1, 2024, must include elevated foundations to meet these new standards.

Charleston Homeowners: Schedule a Free Foundation Inspection

Mount Valley Foundation Services work truck

Charleston’s new flood-resistant construction methods proactively reduce future flood risks and promote sustainable development. It addresses environmental challenges head-on while protecting its residents.

If you reside in Charleston, SC, or nearby areas and need expert foundation care, contact Mount Valley Foundation Services. We offer free inspections and tailored repair strategies to safeguard your foundation before the next storm.

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Foundation Repair FAQs

Can landscaping affect water entry into my foundation?

Absolutely. Improper landscaping that directs water towards your home can increase the risk of water entering through the foundation.

How can hurricanes cause foundation damage?

Hurricanes can lead to foundation damage through flooding, soil erosion, and the intense pressure of wind and water, which can create cracks and instability.

Can pruning tree roots stop them from damaging my foundation?

Pruning can help, but it must be done carefully to avoid harming the tree; consulting an arborist is advisable.

Shaye Glisson

Shaye is an SEO Content Writer for Groundworks with over twelve years of experience creating helpful content across various industries, including home services and retail. She is a Gulf Coast native and writes from her firsthand knowledge of the area's hurricane and flood impacts on the local community. In her free time, Shaye enjoys exploring the local food and music scenes.

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