This article summarizes every section in plain language, with the relevant clause numbers of the Ministerial Regulation, a timeline diagram and a 3D model showing which building groups require soil investigation, plus the most common question: “Do you need soil boring results for a building permit?”
What is the 2023 Foundation Ministerial Regulation?
The Ministerial Regulation Prescribing Building Foundations and Ground Supporting Buildings B.E. 2566 (2023), known in the construction industry simply as the "2023 Foundation Ministerial Regulation", is the new set of foundation rules that replaced Ministerial Regulation No. 6 (B.E. 2527 / 1984), which had been in use for almost 40 years. It was published in the Royal Gazette on 31 August 2023 and has been in force since 28 February 2024.
The key content of this Ministerial Regulation comes down to 3 main points: (1) large buildings must have a soil investigation report covering at least 3 points to accompany the design calculations; (2) the Factor of Safety for spread footings, piles and retaining walls is now clearly set in law; and (3) the criteria for soil and pile testing have been raised in line with international standards.
Published in the Royal Gazette on 31 August 2023 → in force once 180 days had passed, i.e. from 28 February 2024 → Ministerial Regulation No. 6 (B.E. 2527 / 1984) was repealed on the date the new rule took effect. Projects that applied for permits before that date are covered by a transitional provision (Clause 33) allowing the old criteria to continue to apply.
The diagram below combines the legal timeline and the five main topics, with clause numbers, in a single picture. Use it as a map before reading the details of each section.
Why was a new Ministerial Regulation needed?
Ministerial Regulation No. 6 (B.E. 2527 / 1984) was issued under the Building Control Act B.E. 2522 (1979) and had been in force for a very long time, while soil investigation technology, pile testing and design standards had moved far ahead. The Ministry of Interior therefore issued a new Ministerial Regulation in 2023 to modernize the criteria, align them with international standards and improve safety of life and property. Foundation requirements were split out into a dedicated regulation, alongside the Ministerial Regulation on Structural Design of Buildings B.E. 2566 (2023), which covers the superstructure.
In addition, there is a Ministry of Interior Notification (issued 30 August 2024), secondary legislation that sets out further technical details, such as design methods for spread footings and precast concrete piles, and criteria for testing soil bearing capacity and pile resistance — so design engineers need to read the Ministerial Regulation and the Notification together.
Structure of the Ministerial Regulation: 5 key topics
1. Soil investigation report (Clause 5) — which buildings, how many points
The following 4 groups of buildings must have a foundation soil investigation report for the construction site covering at least 3 investigation points to accompany the design calculations:
- High-rise buildings
- Extra-large buildings
- Large buildings that are controlled-use buildings and have 4 or more floors
- Buildings of 4 or more floors in land subdivision projects
The report must be prepared or certified by a “reliable institution” as defined in Clause 2 of the Ministerial Regulation, and must contain the full minimum content, such as a borehole location plan, soil layer data (Boring Log), field and laboratory test results, groundwater level and a summary of soil properties for design — see every item in What must a legally compliant soil investigation report contain? For guidance on the number and depth of boreholes for ordinary buildings, read How many boreholes, and how deep, are enough?
2. Without soil boring results (Clause 7) — the law sets very low capped values
For buildings outside the mandatory groups and without a soil investigation report, the law sets conservative "allowable bearing pressure" and "pile skin friction" values, which are lower than the values usually obtained from actual soil boring. As a result, footings must be larger and piles longer or more numerous — so soil boring usually pays off in total cost. Read the detailed comparison in Without soil boring, what values does the law allow?
3. Spread footings (Clauses 15–16) — FS ≈ 3 and the Plate Bearing Test condition
The allowable bearing pressure of soil under a spread footing may not exceed 33 percent (about one third) of the bearing capacity of the foundation soil (equivalent to a factor of safety of about 3), and to use an allowable bearing pressure above 200 kilopascals (about 20 t/m²) it must be verified by a Plate Bearing Test — read the legal conditions for this test in When does a Plate Bearing Test become mandatory? and the test principles in What is a Plate Bearing Test?
4. Pile foundations (Clauses 24–25, 28) — the source of the value sets the usable cap
The allowable resistance of a pile depends on the "source" of the value: the more reliable the method of proof, the higher the value the law allows (see the in-depth article with examples in How much load can a pile carry by law? The 40/50/40 criteria):
← Scroll to see the full table →
| Source of resistance value | Applicable up to | FS equivalent |
|---|---|---|
| Calculated from the soil investigation report (static method) | 40% of ultimate resistance | 2.5 |
| Tested by the static method (Static Load Test) | 50% | 2.0 |
| Tested by the dynamic method (Dynamic Load Test) — must be calibrated against the static method | 40% | 2.5 |
Read the comparison of the two test methods under the new law in Dynamic vs Static Load Test: which should you choose?, with details of each test in Dynamic Load Test (PDA) and Static Pile Load Test
There are also important site requirements, such as: piles carrying more than 40 t each must comply with what the engineer responsible for the design and calculations certify (Clause 25); the design must accommodate pile eccentricity of at least 75 mm (Clause 28, see Pile deviation over 75 mm: what to do); and soil layers must be classified by law for skin friction calculation (see How does the law classify soil layers?)
5. Retaining walls (Clause 31) — all 3 FS values defined
Retaining walls must be designed to resist earth pressure, water pressure and other loads, with forces calculated as prescribed by the Minister, and retaining walls with a base must have minimum factors of safety in 3 respects: sliding 1.50, overturning 2.00 and soil bearing capacity 3.00 — read the details in Retaining walls under the new law
Do you need soil boring results for a building permit?
Short answer: not for every building — but since 28 February 2024, for the 4 groups above (high-rise buildings, extra-large buildings, large controlled-use buildings ≥4 floors and buildings ≥4 floors in land subdivision projects), soil investigation is no longer "optional". It is a legal requirement to have a report covering at least 3 investigation points before submitting the design calculations.
Two main laws currently govern the structural and foundation aspects of building permit applications:
← Scroll to see the full table →
| Law | In Royal Gazette | Takes effect |
|---|---|---|
| Ministerial Regulation Prescribing Building Foundations and Ground Supporting Buildings B.E. 2566 (2023) (Foundation Ministerial Regulation) | 31 August 2023 | 28 February 2024 |
| Ministerial Regulation Prescribing Structural Design of Buildings and the Characteristics and Properties of Materials Used in Building Structures B.E. 2566 (2023) | 6 September 2023 | 5 March 2024 |
The 3D model below shows all 4 groups of buildings that the law requires to have a soil investigation report of at least 3 points, compared with an ordinary house that is not required to but should still have soil investigation.
The local official's view: design calculations must show a "source"
When reviewing a building permit application, the local official (local administrative organization, municipality, subdistrict administrative organization or Bangkok district office) checks whether the foundation calculations use soil values from a source the law accepts — with a soil investigation report, the engineer can use values from actual soil properties; without one, only the legal capped values may be used; and for buildings in the mandatory groups, a report of ≥3 investigation points is an indispensable document. In addition, local officials in some areas may ask for soil boring results even when a building is not in a mandatory group, especially in soft-soil areas, newly filled land or near water bodies.
What about 2–3 storey houses or small buildings?
For houses and small buildings outside the mandatory groups, the law does not directly require a 3-point soil boring report to be attached, but that does not mean you do not need to know the soil conditions, because:
- Foundation calculations still need a source — foundations must be stable and strong enough to carry the building and transfer the load safely to the ground; the values used must be based on actual soil data or criteria the law accepts
- Some local officials ask for soil boring results — even when a building is not in a mandatory group
- The real risk is on site — house settlement and cracks from differential foundation settlement often result from guessing the soil conditions; repairs later cost many times more than one soil boring hole (see Signs of foundation problems)
In short: for small buildings, "not required by law, but recommended by engineering", especially for houses on piles or built on fill — read more in Does a 2-storey house need soil boring? and Why soil boring before building a house
Foundation documents to prepare for a permit application
- Structural and foundation design calculations, signed by the design engineer
- Foundation soil investigation report — at least 3 investigation points for buildings in the mandatory groups, with a borehole location plan, Boring Logs, test results and groundwater level
- The report must be signed and certified by a civil engineer licensed by the Council of Engineers (COE), and prepared/certified by a reliable institution as defined by law
A soil boring report without a certifying engineer's signature, or without the full content required by law, cannot be used to support the design calculations in a building permit application — always check before hiring that the provider delivers a complete report. See the checklist in What must a legally compliant soil investigation report contain?
Who is affected?
- Project owners / property developers — subdivision projects with buildings of 4 floors or more must budget time and money for ≥3 soil borings from the design stage
- Contractors — pile testing criteria and site tolerances (such as pile eccentricity) are set by law, not just by the project specification
- Design engineers — calculations must cite the source of soil values consistent with the legal FS
- Existing projects — projects that applied for or received a permit before 28 Feb 2024 are covered by a transitional provision (Clause 33) allowing the old criteria to continue to apply
Summary: what the 2023 Foundation Ministerial Regulation changes
The 2023 Foundation Ministerial Regulation turns many "good practices" into "legal requirements" — from the number of soil investigation points and the factors of safety for every foundation type to the pile testing criteria. Anyone starting a new project should plan soil investigation and pile testing to comply with the law from the outset, to avoid setbacks when applying for a permit.
This article summarizes the key points of the law for general understanding only. It is not legal advice or project-specific engineering advice. Actual design and document submission should be carried out by a licensed civil engineer, and the full text of the Ministerial Regulation should always be checked.