Pad Size for a Concrete Wall

Compact Soil

• Concrete walls are normally built on footings, or specialized slabs that spread the weight of the the concrete to avoid having it concentrated on a small area. The footing size depends upon the size of the wall and the compaction of the dirt. Contractors first measure the load-bearing value of soil to determine how much weight it can safely handle. The higher the load-bearing value of the soil, the more weight can be placed upon it without fear of a collapse during construction.

Footing or Pad Width

• For soil at the low extreme of weight-bearing, the footing or pad under a standard 8-inch-thick, one-story concrete wall must be 22 inches wide. At the other extreme of very dense soil, the footing can be only 9 inches, or just bigger than the wall. Use larger sizes for footing and pads even if the soil is dense, because a strong foundation is best.

Pads and Walls

• A slab or pad level with the ground still requires a wider area directly underneath a concrete wall along the side of the pad. For example, if a 15-by-15-foot concrete pad is used as a patio and only one side has a concrete block wall, which is 5-feet high, then the weight of that wall might force the other end of the pad up, like a playground see-saw. Building the wall about two inches in from the edge of the pad and adding an extra two inches of concrete underneath the pad and to both sides of the wall will better distribute its weight over a considerably wider area.

Building Codes

• Concrete pads and slabs are done to code in most areas. The local controlling authority might be the state, county or municipality. The code determines how thick and wide slabs and pads must be for various projects and how wide and deep the footings are to be. The codes take into account the soil compactness and how deep the soil freezes in the winter. A contractor must adhere to the code when working on a project, or else it may not be approved by the inspector.