How Many DPT Standards Cover Piling Work?

Four main DPT standards deal directly with piling: 1106-64, 1251, 1252-51 and 1551-51. DPT is the abbreviation used here for standards issued by the Department of Public Works and Town and Country Planning. Each standard has its own number, usually followed by the year of issue — for example, DPT 1106-64 is the edition issued in B.E. 2564 (2021).

Dynamic pile load testing equipment on site, following DPT 1252-51
On-site pile testing references DPT standards alongside ASTM (Photo: SPN Soil Engineering)

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StandardCoversWhen to use
DPT 1106-64Piling work standard, covering materials, driving, cast-in-place boring, acceptable tolerances and when testing is requiredThroughout piling work; the parent standard
DPT 1251Static Axial Pile Load TestWhen capacity must be proven by applying real load
DPT 1252-51Dynamic Axial Pile Load TestWhen the capacity of many piles must be checked in limited time
DPT 1551-51Pile Integrity TestWhen you need to check whether the pile shaft has cracks or necking

Put simply, DPT 1106-64 says how piling work must be done and when testing is required, while the other three standards say how each test method must be carried out.

The diagram below runs from DPT 1106-64 down to the conditions that trigger testing, then splits into the three test standards. Look at the “Answers” strip in each box: they fall into a load-capacity group (1251 and 1252-51) and a pile-integrity group (1551-51).

Diagram of DPT piling standards, showing that DPT 1106-64 is the parent standard that defines the work and the reasons for testing, while DPT 1251, DPT 1252-51 and DPT 1551-51 each answer a question on either load capacity or pile integrity A hierarchical conceptual diagram. The top frame is DPT 1106-64, the piling work standard and parent document, covering materials, driving and cast-in-place boring, pile splicing, a position tolerance of no more than 50 or 75 millimeters and an inclination of no more than 1 percent of the length, and specifying when testing is required. On the right of the same frame are the documents referenced with it: the TIS 395 to 399 series for precast concrete piles, EIT 1019 for wet-process bored piles, and DPT record forms 1106-1 and 1106-2. From the top frame, three arrows run down through condition boxes. The left arrow is: if the drawings do not specify a test method, the default is the static method, leading to DPT 1251 Static Load Test, which applies real load in increments and measures settlement directly, used together with ASTM D1143. The middle arrow is: if the drawings specify the dynamic method, leading to DPT 1252-51 Dynamic Load Test or PDA, which strikes the pile head with a drop weight, measures the stress waves and back-calculates capacity with CAPWAP, used together with ASTM D4945. The right arrow is: if a pile is cracked and repaired or a bored pile is misshapen, leading to DPT 1551-51 integrity testing, which taps the pile head with a small hammer and reads the reflected wave; the method per ASTM D5882-16 was withdrawn by ASTM in 2025. Each box has a small sketch of the test method and a strip showing the question that standard answers. Below the boxes, brackets group 1251 and 1252-51 as answering load capacity and 1551-51 as answering pile shaft integrity; the two groups answer different questions and cannot replace each other. The bottom strip summarizes three points: DPT is usually cited in contracts and drawings while ASTM gives test method details, an integrity result does not indicate load capacity, and when citing ASTM the edition year should be stated. DPT piling standards: which one answers what Conceptual diagram DPT 1106-64 Piling work standard (parent) Covers: materials · driving / bored · splicing Offset ≤ 50 / 75 mm · tilt ≤ 1% of length and sets “when” testing is required Related documents TIS 395–399 Precast piles EIT 1019 Wet-process bored piles DPT Form 1106-1/-2 Record forms If no test method specified Default = static method DPT 1251 Static Load Test Static method Apply real load in steps Direct settlement Answers How much load can it take? Takes time and space Used with ASTM D1143 If dynamic method specified Many piles in one day DPT 1252-51 Dynamic (PDA) Dynamic method Drop weight hits pile head Measure stress waves Answers How much load can it take? Back-calculate (CAPWAP) Used with ASTM D4945 If cracked+repaired / misshapen Integrity check required DPT 1551-51 Seismic (PIT) Integrity test Tap head with small hammer Read reflected wave Answers Is the shaft sound? Cracks · necking · discontinuity ASTM D5882-16 withdrawn 2025 Answers “load capacity” Answers “integrity” ≠ Different questions, not interchangeable 1 DPT = cited in contracts/drawings ASTM = test method details 2 Integrity pass ≠ capacity OK Confirm capacity: 1251 / 1252-51 3 Cite ASTM with edition year D5882-16 withdrawn in 2025
DPT piling standards diagram: DPT 1106-64 defines the work and the cases that require testing, DPT 1251 and 1252-51 answer load capacity, and DPT 1551-51 answers pile shaft integrity, with the ASTM standards used alongside — conceptual diagram

What Does DPT 1106-64, the Piling Work Standard, Cover?

DPT 1106-64 is the piling work standard and covers both driven piles and bored piles. The provisions contractors and owners run into most often are:

  • Pile splicing — precast concrete piles may be spliced into no more than 2 segments and must be joined by electric welding. The steel plates cast into the pile must be at least 9 millimeters thick, and the splice plates at least 6 millimeters thick. The standard prohibits splicing in 3 cases: piles that must resist lateral loads, piles in soil layers at risk of sliding, and piles whose tips bear on sloping rock.
  • Hammer weight — the driving hammer must weigh at least 70 percent of the pile weight and no less than 3 metric tons.
  • Spacing during boring — a new bored pile must be at least 6 times the diameter of the larger pile away, center to center, from any pile cast within the previous 24 hours; in soft clay a greater spacing may be needed.
  • Position tolerance — for foundations with 1–2 piles, an offset of no more than 50 millimeters is allowed; for foundations with 3 or more piles, no more than 75 millimeters; and the center of a pile group may be offset by no more than 50 millimeters. For piles larger than 600 millimeters, the maximum tolerance is at the discretion of the design engineer. If measured offsets exceed the limits, see what to do when pile offset exceeds 75 mm
  • Inclination — deviation from vertical must not exceed 1 percent of the pile length.
  • Record forms — driving work uses DPT Form 1106-1 and bored pile work uses DPT Form 1106-2. These two records are the traceable evidence when disputes arise.

The standard also states that using any standard other than those referenced requires approval from the Building Control Committee or the Council of Engineers Thailand, and that if another standard conflicts with DPT 1106-64, this standard prevails. Wet-process bored piles must comply with EIT standard 1019.

When Does DPT Require Pile Testing?

DPT 1106-64 clearly sets out the cases in which piles must be tested. This is often overlooked, because people tend to assume the standard only describes test methods. There are 4 common cases:

  • Drawings do not specify a test method — if the drawings or the project-specific specifications do not detail a load test method, the default is a static load test per DPT 1251. This answers a question contractors ask often: what to do when the spec is silent.
  • Cracked pile repaired — the damaged concrete of a cracked pile must be chipped out and recast, and after redriving, a pile integrity test must be performed.
  • Bored pile shape deviates from the design — if the size or shape deviates, test by the vibration (sonic) method or another method approved by the supervising engineer.
  • Widespread damage to driven piles — if 10 percent of driven piles are damaged, drive an additional 10 piles for checking. If these are also damaged, the work is deemed non-compliant with the standard and must be verified by engineering analysis or testing.

For how many piles should be tested, see how many piles need to be tested

What Is DPT 1251, the Static Load Test Standard?

DPT 1251 is the standard for static axial pile load testing, known on site as the Static Load Test. The method applies real load to the pile head in increments and measures the settlement at each increment.

Its advantage is that load and settlement are measured directly, closest to actual service conditions. Its limitations are that it takes considerable time and space and requires a reaction frame or kentledge, so it costs much more than other methods. Reports usually cite it together with ASTM D1143/D1143M-20e1. For the procedure, see Static Load Test: pile testing by applying real load

How Does DPT 1252-51 Dynamic Testing Differ from DPT 1251?

DPT 1252-51 is the standard for dynamic axial pile load testing, which corresponds to the Dynamic Load Test or PDA in site terminology. A drop weight strikes the pile head and the stress waves traveling down and reflecting back are measured to back-calculate the load capacity.

Example force and velocity signals from a dynamic pile load test, used to assess signal quality per DPT 1252-51
The recorded force and velocity signals are the main evidence DPT 1252-51 uses to judge test quality

Unlike DPT 1251, each pile takes only hours, and many piles can be tested in a single day, making it well suited to quantitative checking across a project. However, the result is back-calculated from signals rather than a direct settlement measurement, so its quality depends on signal quality and the CAPWAP analysis. Reports usually cite it together with ASTM D4945 (current edition D4945-26). For how to read the results, see how to interpret PDA test results, and for an overview of the method see what is a Dynamic Load Test (PDA)

What Does DPT 1551-51 Pile Integrity Testing Check?

DPT 1551-51 is the standard for pile integrity testing, corresponding to the Seismic Integrity Test or Low Strain Pile Integrity Test. The pile head is tapped with a small hammer and the reflected wave is measured to see whether the pile shaft has cracks, necking or discontinuities.

Pile integrity testing by the sonic method at the pile head, following DPT 1551-51
Seismic Integrity Test checking pile shaft integrity per DPT 1551-51 (Photo: SPN Soil Engineering)

It must be clearly understood that DPT 1551-51 does not indicate load capacity. A pile that passes the integrity test has no detectable anomalies in its shaft; it does not mean the pile can carry its design load. To confirm capacity you need DPT 1251 or 1252-51. Read more at what is a Seismic Integrity Test

DPT vs ASTM: How Do They Differ and Which Should You Use?

You don’t have to choose, because the two serve different purposes. DPT standards are Thai construction standards that are usually cited in contracts and specifications, while ASTM standards are international test method standards that specify procedures and equipment in greater detail. In practice, test reports for projects in Thailand usually cite both together.

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Test methodThai standardInternational standard used alongside
Static Axial Pile Load TestDPT 1251ASTM D1143/D1143M-20e1
Dynamic Axial Pile Load TestDPT 1252-51ASTM D4945 (current edition D4945-26)
Pile Integrity TestDPT 1551-51Method per ASTM D5882-16 (withdrawn by ASTM in 2025)

Note: ASTM D5882-16 was withdrawn by ASTM in 2025, so integrity testing in Thailand relies on DPT 1551-51 as the main criterion. When citing ASTM in a report, always state the designation and year clearly. For a detailed comparison of the ASTM side, see ASTM D5882, D4945, D1143: how they differ. DPT 1106-64 also references the TIS 395 to 399 series of product standards for precast concrete piles and EIT standard 1019 for wet-process bored piles.

The 3D view below brings all three methods onto one site, each labeled with its DPT standard and the ASTM standard used with it. The frame on the right helps you choose a standard by the question you need answered: for load capacity, see items 1–2; for pile shaft integrity, see item 3.

3D model of a pile site with three test methods carried out at once, each labeled with its DPT standard and companion ASTM standard, plus a frame for choosing a standard by the question to be answered A conceptual 3D view of a fifteen-pile layout on a soil block cut away to show a cross-section. The upper layer is soft clay and the lower layer is sand. The front row of piles shows the shafts reaching the sand layer. Three test setups are on the same site. Setup one, at the rear right, is a kentledge Static Load Test: timber cribbing on both sides, a main beam, a jack and three tiers of kentledge blocks over a representative pile, labeled DPT 1251 with ASTM D1143. Setup two, on the left, is a Dynamic Load Test or PDA, with an orange guide frame and a drop weight above the pile head and gauges at the pile head cabled to the PDA unit, labeled DPT 1252-51 with ASTM D4945. Setup three, in the front row, is a Seismic Integrity Test, using a hand-held hammer to tap a pile head fitted with an accelerometer, cabled to a portable recorder; on the soil cross-section, blue arrows show the wave traveling down the pile and reflecting back from the toe, labeled DPT 1551-51. The frame on the right is titled choose by the question you need answered. Item one: you need a result from real loading on how much the pile can carry — use DPT 1251, which measures settlement directly but takes considerable time and space. Item two: you need to check the capacity of many piles in limited time — use DPT 1252-51, which can test many piles in one day but back-calculates from signals. Item three: you need to know whether the pile shaft has cracks or necking — use DPT 1551-51, which does not indicate load capacity. An orange box states that if the drawings do not specify a test method, DPT 1106-64 sets the static method per DPT 1251 as the default, and a note says the method, number and location of test piles are set by the responsible engineer. This is a conceptual view, not an actual pile layout. 3D model: three methods, three standards, one site Not to scale 2 Dynamic (PDA) DPT 1252-51 · ASTM D4945 1 Static Load Test DPT 1251 · ASTM D1143 PDA unit 3 Seismic (PIT) DPT 1551-51 Wave travels down, reflects from toe Section: soft clay / sand layer Choose by your question 1 Can it really carry the load? Need a result from real loading DPT 1251 Direct settlement · slow, needs space 2 Check many piles fast? Limited time, many piles/day DPT 1252-51 Back-calculate (CAPWAP) 3 Is the shaft cracked/necked? Checks shaft continuity DPT 1551-51 Does not give load capacity No test method in drawings? DPT 1106-64 default is the static method per DPT 1251 Agree method with designer first Test method / no. / location set by the responsible engineer Conceptual Not an actual pile layout
3D model: three methods on one site — Static Load Test (DPT 1251 · ASTM D1143), Dynamic Load Test or PDA (DPT 1252-51 · ASTM D4945) and Seismic Integrity Test (DPT 1551-51) — with a frame for choosing a standard by question. Conceptual view, not an actual pile layout; the method, number and location of test piles are set by the responsible engineer.

How Do You Apply DPT Pile Testing Standards on a Real Project?

Owners and contractors can apply DPT standards on a real project at 3 points: before piling starts, during the work, and when receiving the test report.

1. Check the spec before work starts — open the specifications and check whether a test standard is specified. If not, the default under DPT 1106-64 is the static method, which costs much more and takes much longer than other methods, so agree on this clearly with the design engineer before piling begins. For the legal requirements, see separately pile testing under the Foundation Ministerial Regulation B.E. 2566 (2023)

2. Keep the record forms complete — DPT Form 1106-1 for driving and DPT Form 1106-2 for boring are the evidence you can refer back to when pile quality is questioned.

3. Check that the report cites the standard actually used — a good report states the standard, method and equipment used, and is signed and certified by a civil engineer licensed by the Council of Engineers Thailand (COE). See what it should contain in the pile test report checklist

As for fees, SPN’s dynamic load testing (PDA) is about THB 5,500 per pile, pile integrity testing (Seismic Integrity Test) is about THB 100–150 per pile, and a Static Load Test ranges from THB 50,000–150,000 or more per pile, depending on the test load and the reaction system used. These prices exclude travel and equipment mobilization, which are charged according to the distance to site. For other test methods or jobs with special conditions, contact us for a free quotation within 24 hrs.

⚠️ This article provides general information

This content summarizes the key points of the standards for a basic understanding and does not replace the full standards. The test method, number of piles and acceptance criteria for each project must be set by the responsible engineer, always with reference to the actual standards.