Post Foundation Embedment

There are a number of factors that determine the size of the posts you use on your building. Wall height and wind conditions are two that come to mind immediately, but many other factors are considered too. Attic trusses, or floor joists create loads that may require larger posts, glulams, or closer post spacing.

Post foundation embedment is determined by soil bearing capacity and frost heave. If a cold winter in your area is a low of 40° and the soil is rocky gravel then a 24" depth, 12" diameter hole with a 6-8" footer may be sufficient.

Northern climates mean deeper pole embedment to combat frost heave. Frost heave creates an upward thrust or deforming of the soil near the grade and below the grade to certain levels.

Soil that is sandy, has clay content, or includes silt does not have the load bearing capacity of gravel and rocky soil.

It is always a good idea to check with local authorities about soil consistency in your county. Some areas have very consistent soil while others fluctuate wildly.