4.8.1 Applications & Limitations

Minimal excavation foundations in both pier and perimeter wall configurations are suitable for residential or commercial structures up to three stories high (see Figure 4.8.1). Accessory structures such as decks, porches (see Figure 4.8.2), and walkways can also be supported, and the technology is particularly useful for elevated paths and foot-bridges in open spaces and other environmentally sensitive areas (see Figures 4.8.3 and 4.8.4). Wall configurations are typically used on flat to sloping sites up to 10 percent, and pier configurations flat to 30 percent.

The minimal excavation foundation approach can be installed on all soils, provided the material is penetrable and will support the intended type of piles. Soils typically considered problematic due to high organic content (top soils or peats) or overall bearing characteristics may often remain in place provided their depth is limited and the pins have adequate penetration into suitable underlying soils.

These systems may be used on fill soils if the depth of the fill does not exceed the reaction range of the intended piles. Fill compaction requirements for support of such foundations may be below those of conventional development practice in some applications. In all cases, for both custom and pre-engineered systems, a qualified engineer should determine the appropriate pile and connection components and define criteria for specific soil conditions and construction requirements.


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Fig4-8-1_Figure 491
Figure 4.8.1 - Use of minimal excavation foundations for residential dwelling

Single-family dwelling unit constructed over piers. Source: Photo with permission of Pin Foundations, Inc.


Fig4-8-2_IMG_8703
Figure 4.8.2 - Use of minimal excavation foundations for accessory structures
Deck constructed over piers. Source: City of Spokane

Fig4-8-3_Figure 493
Figure 4.8.3 - Footbridge with minimal excavation foundation
Construction of a foot-bridge utilizing minimal excavation foundations at the Auburn Environmental Park in Auburn, Washington. Source: AHBL, Inc.

Fig4-8-4_Figure 494
Figure 4.8.4 - Footbridge with minimal excavation foundation
Completed foot-bridge utilizing minimal excavation foundations at the Auburn Environmental Park in Auburn, Washington. Source: AHBL, Inc.