Quick Guide for the Pro-Builder

Normal Soil Conditions 

Diamond Pier foundations sold through retail outlets are designed for projects that are founded in normal sound soils. Normal soils are typical in most residential neighborhoods throughout the United States and are defined in the International Residential Code (IRC) Table R401.4.1. Presumptive Load-Bearing Values of Foundation Materials. 

For residential applications, the two most common prescriptive bearing soil types relied upon in the IRC table, and in most local codes, are 2000 psf sands/gravels and 1500 psf silts/clays. Diamond Pier foundations sold through retail outlets must be founded in soils with a minimum 1500 psf bearing strength. Supporting soils that do not meet the presumptive bearing strength defined in the applicable code for your area will not provide expected foundation capacity, and their bearing capacity may need to be determined by a soils investigation. Ask your local code official for soil information regarding your site. Additional soils information may also be available at the U.S. Geological Soils Survey website managed by the U.S. Department of Agriculture. 

Supporting Soils 

Some soils may not be appropriate for supporting Diamond Pier foundations. Some examples include soils that are weaker than 1500 psf, soils that are highly expansive, shifting or sliding soils, soils on slopes greater than 2:1 (27 degrees), contaminated soils, or soils where traditional concrete piers, accepted by local codes, are unable to provide adequate bearing to support the loads of the project or to protect the structure from the negative effects of frost heave. Where unsound soils exist, a registered design professional may be required to review the project. 

Soils can also be weakened when they retain standing water or are improperly drained, and in certain types of soil this can also cause heave problems. A site depression with standing water or the potential for water to pond, pool, or saturate the soil may be an indication that the soil is not sound. Downspouts that discharge at or near a foundation may also cause soil problems, and setting a Diamond Pier foundation adjacent to any water body should be considered carefully. Depending on the variables involved, soils at the edge of or within lakes, ponds, rivers, streams, or tidal zones may be considerably weaker (as much as 40% or more) than dry or well-drained soils. Soils adjacent to existing foundations may also have been improperly or loosely backfilled, which may also cause poor drainage or poor soil conditions. Be sure to inform your project designer if any of these conditions exist. 

Please contact PFI if you have any questions regarding your project or soil conditions, and/or the proper use of the Diamond Pier product or "Residential Diamond Pier Load Chart," provided in Table 1 of the Installation Manual. 

Notes: 

1. This load chart is intended for simple structures supported by columns, posts, and beams loaded up to, but not exceeding, the stated capacities. It is not intended for structures with asymmetrical, rotational, overturning, or dynamic forces. Intended uses are described in section 2.0 of ICC-ES prescriptive bearing evaluation report ESR-1895. For projects that exceed the capacities or limitations defined herein, or the intended uses described in ESR-1895, contact PFI for additional information or site-specific capacity evaluation. See also the Use and Applications download at www.diamondpiers.com.
2. Capacities shown are tested to a Factor of Safety of 2, and are applicable in properly drained, normal sound soils only, with minimum soil bearing capacities as indicated. Copies of the field test reports are available from PFI upon request.
3. See IRC Table R401.4.1, “Presumptive Load-Bearing Values of Foundation Materials,” for a full description of applicable 1500 psf and 2000 psf soil types. For soils below 1500 psf, or soils with unknown characteristics, additional site and design analysis is required. For soils above 2000 psf, the values in this chart shall apply. 
4. All capacities use four pins of the specified length per foundation. Pin length includes that portion of the pin embedded within the concrete head. See “Check Your Layout” on page 9  in the Installation Manual for more information on pin/pier layout and spacing restrictions.
5. For professional engineers designing for short-term transient loads, contact PFI for further information. 

Get a Building Permit: 

The Diamond Pier foundation is compliant with the 2006, 2009, 2012, 2015 & 2018 IRC. Visit our Code Compliance page to learn more. 

Most likely you'll need to apply for a building permit for your project. You'll need to submit the following Diamond Pier documents with your permit application. Please contact us with any questions or issues, or if more testing/documentation is required. 

Locate Buried Utilities: 

All underground utility lines must be located and properly marked by your local official utility locating service, and all privately run lines must also be identified and located by the proper authority. If there are any electrical lines in the area, de-energize the power source prior to installing the Diamond Pier foundations. Never allow bodily contact with uninsulated portions of the automatic breaker hammer. Wear properly rated rubber-insulated gloves and boots. In addition, if underground utilities are located on the site, check with your local utility locating service to confirm required safety zones. You must ensure that the horizontal pin distance for your foundation will have adequate horizontal clearance to be well outside all safety zones, including the 6” Diamond Pier (DP) safety zone. See Figure 2 and Table 2 in our Full Installation Manual.

Full Installation Manual.