Helical pile foundation details are the parts of the structural drawings that tell the installer what pile to use, where it goes, how deep and how hard it has to be turned, and how its top connects to the concrete. On most new builds that information is spread across four places: the general notes, a pile schedule, the foundation plan and the cap and grade beam details. Once you can read those four, you can check a bid and catch a missing number before the rig shows up. The installation log will make sense when it comes back, too.
Where the helical pile information lives in a drawing set
| Part of the set | What it tells you | Who uses it most |
|---|---|---|
| General notes | Design loads, minimum torque and depth rules, product standard, corrosion protection, inspection | Installer, inspector |
| Pile schedule | Each pile type with its shaft, helices, loads, torque and depth | Installer |
| Foundation plan | A mark and a location for every pile, plus grade beam and footing outlines | Installer, surveyor, concrete crew |
| Cap and grade beam details | How the pile top is cut, capped and embedded in concrete, rebar, void forms | Concrete crew, inspector |
The building code expects that layout. IBC 1810.4.3, which Denver adopts, says a plan showing the location and designation of deep foundation elements “by an identification system” goes to the building official before installation. Each pile’s record then carries the same ID as the plan. That’s why every pile on the plan has a mark like P1 or HP-12, and why the log you get back uses those exact marks.
The general notes: the rules every pile has to meet
The general notes are the paragraph block most people skip. They hold the rules that apply to every pile on the job:
- the design standard and the evaluated product, usually an ICC-ES evaluation report number
- the soils report the design is based on
- the minimum installation torque and minimum depth, and which one governs
- what to do if the pile reaches maximum torque before minimum depth
- corrosion protection, usually hot-dip galvanizing
- special inspection and load testing
IBC 1810.4.11 says helical piles “shall be installed to specified embedment depth and torsional resistance criteria.” A good note says what both numbers are and how torque is measured. The federal guide specification for helical piles, UFGS 31 63 26.60, is a useful model. It compares the average torque over the last 3 feet of penetration with the required minimum. If the pile reaches the minimum torque before the minimum length, installation continues to the minimum length. If it reaches the maximum torque rating first, the installer stops and calls the engineer.
The same spec asks for all steel components to be hot-dip galvanized to ASTM A153 or A123. Whatever your project calls for, the coating belongs in the notes so it can be priced correctly.
Denver adds one local number that should appear somewhere in the notes or details. Its amended IBC 1809.5 sets the frost line at 36 inches below finished grade.
The pile schedule, and how the numbers relate
The pile schedule is a table with one row per pile type. Typical columns are the pile mark, shaft size, helix configuration, design compression and tension loads, minimum torque, minimum depth and the cap type.
The torque number is worked out from the load. Under ICC-ES AC358, ultimate capacity equals a ratio, Kt, times the final installation torque. The default Kt for a 3.0 inch round shaft is 8 per foot. IBC 1810.3.3.1.9 allows half of the ultimate as the working load. Here is how one row might be built:
| Column | Example value | Where it comes from |
|---|---|---|
| Pile mark | HP-1 | Matches the plan |
| Shaft | 3.0 in round | Chosen by the designer |
| Design compression load | 20,000 lb | Structural calculations |
| Required ultimate capacity | 40,000 lb | 2 × design load |
| Minimum installation torque | 5,000 ft-lb | 40,000 ÷ Kt of 8 |
| Minimum depth | Engineer’s value, below the 36 in frost line | Soils report and frost line |
That covers the torque side only. Torque is one of six limits on the pile. The shaft, the couplings and the helix plates each have their own capacity, and the lowest one governs. A manufacturer can also prove a different Kt with load tests, and its evaluation report then lists it.
The foundation plan: marks, locations and tolerance
The plan shows each pile as a symbol with its mark, dimensioned to gridlines or to the building corners. Look at whether piles are dimensioned to their centers, how close they sit to beam ends and corners, and whether battered (angled) piles are shown with their direction.
Piles never go in exactly on the dot, and the code plans for that. IBC 1810.3.1.3 requires the foundation or superstructure to be designed for a mislocation of at least 3 inches. If a pile ends up farther out than the design allows, the engineer decides the fix. UFGS 31 63 26.60 lists the usual answers: a replacement pile next to the one in question, or whatever the structural engineer directs. The same spec asks for an as-installed survey before concrete, giving each pile’s deviation from plan in two directions and its top elevation to the nearest half inch. Many residential jobs don’t require a licensed survey, but checking each pile’s position against the plan before the forms go up still makes sense.
Helical pile cap details
The cap detail shows how the top of the pile connects to the concrete. On new construction the bracket is a direct-load cap: a plate welded to a steel sleeve that slides over the shaft. CHANCE’s ICC-ES evaluation report, ESR-2794, separates these new-construction caps from side-load brackets, which bolt onto existing foundations and carry compression only. New-construction caps are rated for compression and tension.
What the cap detail should show
- the cut-off elevation of the shaft
- the cap plate size and how it is attached
- embedment of the pile and cap into the concrete
- edge distance from the pile to the end or corner of the beam
- the rebar passing over or around the cap
ESR-2794 gives the numbers for the CHANCE system. The center of the shaft sits at least 6 inches from the end or corner of the footing or grade beam. For a fixed-head pile, or any pile that resists tension, the shaft is embedded at least 7.5 inches into the concrete. A tension pile also gets its cap through-bolted to the shaft, and the design professional sets the embedment and reinforcing that carry the uplift.
The building code adds minimums of its own in 1810.3.11. Pile caps are reinforced concrete. Grade beams count as pile caps. The tops of piles are embedded at least 3 inches into the cap. The code also says the soil under a pile cap isn’t relied on to carry vertical load, so the piles carry it all.
Compression and tension details look alike at a glance, so check which one each schedule row calls for. The tension version has the through-bolt, deeper embedment and extra reinforcing, and swapping one for the other in the field is a question for the engineer.
The grade beam section and the void under it
The grade beam section shows the concrete that spans between piles: its width and depth, top and bottom bars, stirrups and the cap embedded in it. On Front Range jobs it often shows something else underneath the beam, a void form.
The Colorado Geological Survey says expansive soil and rock can swell up to 20 percent by volume when wet and push with pressures of 20,000 pounds per square foot or more. A beam resting on that clay can be lifted. With a void form under it, the beam spans from pile to pile and the clay has room to swell without bearing on the concrete. If your soils report calls the site expansive and the section shows no void, ask about it. Our page on why soil testing matters before building covers what that report includes.
What the installation records should show
Once the piles are in, the records should map one to one onto the plan. UFGS 31 63 26.60 lists what a formal record holds for each pile, including:
- date, time and the installation equipment
- type of torque indicator
- pile location and total installed length
- lead section and extensions by manufacturer and catalog number
- installation torque at one-foot intervals
- effective torque and calculated capacity
Denver’s code also requires special inspection for helical piles under 1810.4.12 and 1705.9, so the inspector’s notes sit alongside the installer’s log. If you want a picture of how the work itself goes, see how helical pier installation works.
Checklist before the rig shows up
- Every pile on the plan has a mark, and every mark is in the schedule.
- The schedule gives minimum torque and minimum depth for each pile type.
- The notes say how torque is measured and what happens at maximum torque.
- The corrosion protection is stated.
- Compression and tension caps are clearly separated.
- Cap embedment and edge distances are dimensioned.
- The grade beam section shows the void form if the soils report calls for one.
- The notes name the soils report the design is based on.
Planning a helical pile foundation?
Site Safe Helical Piers installs helical piles for new homes, additions, decks, retaining walls, solar and commercial projects in Denver and along the Colorado Front Range, and can help line up foundation design and geotech reports. See our services, contact us or call 970-673-5615.
