Pin Foundations, Inc.

Diamond Pier foundations support decks, walkways, pergolas, and other simple post-and-beam projects for homeowners and builders. A precast concrete head holds four galvanized steel bearing pins in position. You can start framing as soon as installation is complete.

Pin Foundations, Inc. is the family-owned company behind Diamond Pier. It’s based in Gig Harbor, Washington. Its foundation work includes pre-engineered products and site-specific engineered solutions.

Choose by the load each post carries

The pins spread the load into undisturbed soil, while the concrete head holds their angles under load. The soil carrying those pins is part of your foundation.

PFI recommends the smaller model for smaller, simpler projects and the larger model for larger, more complex structures. Choose by the calculated load at each post. Your loads and pier layout have to stay within the published Residential Diamond Pier Load Chart.

Accessory structures need a close look at their intended use. Diamond Pier lists an art studio as an example, but the described approval excludes support of habitable enclosed dwelling areas. The stated project-size limit is less than 600 square feet. Projects beyond the pre-engineered models’ scope and limitations require site-specific engineering.

Soil capacity decides the foundation route

Diamond Pier requires site-specific engineering where soil capacity can’t be determined. That’s the deciding condition. The pre-engineered foundations require soil with a minimum bearing capacity of 1,500 pounds per square foot.

A Diamond Pier layout in Polson can encounter different bearing conditions from one post to the next because the lot’s moraine can mix boulders, clay, and gravel. Where that variability leaves soil capacity undetermined, site-specific engineering is required.

Wet ground also deserves attention. Water can weaken the soil supporting the pins, and downspout discharge can create soil problems near the foundation. Maintain drainage around the piers and direct downspout discharge away from them.

Settle the layout before driving pins

Building-department approval comes before installation. Project drawings need the product detail and a pier layout consistent with the residential load chart. Crowding piers changes their capacity: spacing below 3 feet between anchor-bolt centers requires a 13 percent bearing-capacity reduction for each closer-spaced pier.

Diamond Pier recommends a minimum two-person crew, and its residential models are usually installed with electric hammers. The listed driving setup uses an automatic driving hammer with a 1⅛-inch hex-shaft driving bit. Before installation, underground utilities must be located, marked, and de-energized, including proper identification and location of privately run lines.

Rocks and roots can obstruct pins. The pins can be removed and the head rotated to change their entry paths, while maintaining the required setbacks from existing foundations and buried obstacles.

Account for frost conditions

Diamond Pier’s pins can move along their axes while the head maintains their alignment. That movement accommodates soil strain from frost heave. The installation manual supplies the frost-depth ratings; sites requiring conventional concrete footings deeper than 60 inches to resist frost heave exceed the residential load chart’s normal-soil limits.

Selected Diamond Pier specifications

These capacities apply to soils with a minimum bearing capacity of 1,500 pounds per square foot. Each pier’s calculated loads must remain within the published residential load chart.

Model	Pin length	Bearing capacity	Uplift resistance	PFI’s project guidance
DP-50	50 inches	3,300 pounds	1,200 pounds	Smaller, simpler projects
DP-75	63 inches	4,200 pounds	1,600 pounds	Larger, more complex structures

Frequently Asked Questions

Can you build on Diamond Pier foundations right after installation?

Yes. You can start framing as soon as Diamond Pier installation is complete, without waiting for poured concrete to cure. That makes the foundation work easier to fit into a short building schedule, provided your plans and pier layout are approved before installation.

Can you install Diamond Pier foundations yourself?

Yes. Diamond Pier allows you to install its foundations without a certified installer and recommends at least a two-person crew. The residential piers are usually driven with electric hammers; a roto-hammer is inadequate. Your driving setup needs to suit the soil, since stiff or dense ground takes more impact energy.

What happens if a Diamond Pier pin hits a rock?

A buried rock or root can block a bearing pin. With Diamond Pier, you can remove the pins and rotate the concrete head to change their paths, as long as the required setbacks remain intact. Removing a soil plug and trying to drive the pin again requires building-official approval.

Can Diamond Pier foundations sit in wet ground?

Diamond Pier footings can sit in wet conditions, but water’s effect on soil strength is the deciding issue. Standing water and poor drainage can weaken the ground carrying the pins and can cause heave problems in some soils. Keep drainage working around the foundation and keep downspout discharge away from it.

Can you bury the concrete head on a Diamond Pier foundation?

Yes. You can bury the Diamond Pier concrete head for appearance, provided you keep access to its top. An adjacent patio or slab also needs room to move without interfering with the foundation or the attached post-and-beam assembly.