The Height of the Concrete Pillars for a Shed Foundation

Types of Pillar Foundations

• Builders construct pillar-type foundations either below-grade or at ground level. Below grade pillar construction methods include concrete tube forms and convention formed and poured footings. On-grade construction methods include precast concrete piers with metal straps or solid concrete blocks topped with wooden nailing blocks. Many builders combine facets of one or many pillar construction methods. For example, builders often pour a footing to ground level with a concrete tube form or conventional forming methods, allow the footing to dry and set a precast pier or block on top of the below-grade footing.

Recommended Pier Height

• Pier height requirements vary according to site-specific factors, such as drainage patterns and climate, and local building codes. Many building authorities allow homeowners to build small utility structures without permits or regard for residential construction requirements. However, to extend the life of wooden framing members, such as posts, floor framing and subfloor decking, you should raise your pillars above ground level. While any height above ground level will reduce exposure to moisture and pests, most piers rise from 6 to 24 inches above grade. Consult a professional or your local building authority before building a taller pillar; tall pillars are often unstable and require special construction or bracing techniques, particularly in zones subject to natural disasters.

Pillar Depth

• Pillar depth is just as important as pillar height. Areas that regularly experience freezing temperatures have specific footing and below-grade column depth requirements. Freezing and thawing cycles cause soil to first contract then heave upward. Frost heave often causes on-grade pillars to shift, damaging both the shed's foundation and framing. Thus, many codes call for pillars in heavy freeze areas to extend at least 6 inches below the average frost line.

Additional Requirements

• Even if your local building authority doesn't require a permit or inspection for your shed, you should heed building code recommendations. Most code requirements result from past experience and testing. Additional pillar requirements include the width of the pillar's footing, concrete pouring and mixing specifications and subsurface drainage guidelines.