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Thickened Edge / Footing Calculator
Calculate the additional concrete needed for thickened edges and integrated footings on a monolithic slab. See slab volume, footing volume, and combined totals.
Slab Dimensions
Thickened Edge
Total depth from top of slab to bottom of footing
Width of the thickened section
Interior Footings (optional)
For load-bearing interior walls that need a thickened strip down the center of the slab.
How Thickened Edges Work
In a monolithic slab foundation, the perimeter of the slab is "thickened" — made deeper — to create an integrated footing. Instead of pouring a separate footing and then a slab on top, everything goes in one pour. The thickened edge typically extends 12-24 inches deep and 12-16 inches wide.
This design transfers the weight of load-bearing walls down through the thickened edge into the soil below. It's approved by most building codes in areas where the frost line is shallow (generally 12 inches or less).
Typical Thickened Edge Dimensions
| Application | Edge Depth | Edge Width |
|---|---|---|
| Residential (single story) | 12 – 18 inches | 12 inches |
| Residential (two story) | 18 – 24 inches | 12 – 16 inches |
| Light commercial | 18 – 24 inches | 16 – 20 inches |
| Interior load-bearing walls | 12 – 18 inches | 12 inches |
Always verify with your local building code and engineer's specifications.
Interior Footings
For interior load-bearing walls, a thickened strip is formed within the slab — typically the same depth and width as the perimeter footing. This is common in larger homes where interior walls carry roof or second-floor loads.
When calculating concrete volume, the interior footing volume is in addition to the slab volume. The extra depth (below the slab thickness) is what adds concrete beyond the flat slab calculation.
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