SPN soil boring rig working on a condominium construction site in central Bangkok, surrounded by high-rise buildings
Soil investigation for a condominium project in central Bangkok — urban work must manage limited space, vehicle access and working hours so as to disturb neighbors as little as possible

What work does SPN carry out in Bangkok and its vicinity?

The work SPN regularly carries out in Bangkok and its vicinity covers every stage of a project, from pre-design through construction:

  • Soil investigation (Soil Boring + SPT) — houses, commercial buildings, condominiums, high-rises and warehouses in the metropolitan area, with lab tests and reports certified by an engineer
  • Pile testing — Seismic Integrity Test to DPT 1551-51 for testing every pile · Dynamic Load Test (PDA) to ASTM D4945 and DPT 1252-51 · Static Load Test for high-rise buildings
  • Instrumentation — Inclinometers, settlement plates and piezometers for deep excavations and fills on soft clay
  • Non-destructive structural testing (NDT) — GPR scanning of the ground and structures, Rebound Hammer, UPV and core tests for old buildings, extensions and building purchases/sales
  • Geotechnical design — foundations, retaining walls and temporary earth-retaining systems on soft clay

How does soft Bangkok clay affect soil investigation?

Bangkok and its vicinity sit on a layer of soft clay (Soft Bangkok Clay) about 12–20 meters thick that has low bearing capacity and keeps settling, so almost every building needs piles to transfer loads down to the dense sand layer below. Soil investigation in this area differs from other regions in several ways:

  • Boreholes must reach the bearing sand layer — not just pass through the soft clay, because engineers use the SPT N-values of the sand layer to set the pile tip level. The EIT guideline for buildings of up to 5 stories in Bangkok is about 30 meters, getting deeper with building height.
  • Soil layers can differ at the district level — from actual projects and public data, the Bang Phli area of Samut Prakan has upper soft clay up to about 26 meters thick, Bang Rak has a very soft mud layer at about 38–50 meters depth, and the Thonburi side often has silty sand seams within the soft clay.
  • Undisturbed samples of the soft clay must be taken (Shelby tube, ASTM D1587) for Unconfined Compression and Consolidation tests, which are used to assess settlement and pile skin friction.
  • Ground settling around buildings (Negative Skin Friction) — land subsidence and fill settlement make the ground around a house settle differently from the house itself on piles; soil data is needed to design for this.
Soft Bangkok clay, what soil investigation must do about it, and how soil layers differ by district The left image is a typical soil section of Bangkok and its vicinity: fill and topsoil at the top, followed by soft clay about 12 to 20 meters thick, stiff clay, and the dense sand layer used as the pile tip bearing layer. Boreholes must go through the soft clay down to the sand layer; the EIT guideline for buildings of up to five stories is about 30 meters. In the soft clay, undisturbed samples are taken with thin-walled tubes per ASTM D1587, and house piles carry downdrag from the settling soil around them, or Negative Skin Friction. The right image shows simplified sections of three districts: Bang Phli has upper soft clay up to about 26 meters thick, Bang Rak has a very soft mud layer at about 38 to 50 meters depth, and the Thonburi side often has silty sand seams within the soft clay. Values shown are typical for the area, not design data. Bangkok soft clay — bore to sand; varies by district Not to scale Typical section, Bangkok Metro Soft clay ~12–20 m thick Stiff clay Dense sand Pile tip layer Bore ~30 m ≤ 5 stories (EIT) SS + SPT ST (ASTM D1587) Downdrag on pile (Negative Skin Friction) Varies by district 0–50 m Bang Phli Bang Rak Thonburi 0 10 20 30 40 50 Upper soft clay up to ~26 m Very soft mud ~38–50 m Silty sand seams in soft clay So adjacent-plot data can't substitute Typical area values (EIT guideline, field work), not design data
Left: typical section of Bangkok and vicinity — boreholes must pass through the soft clay down to the bearing sand layer (about 30 m for buildings of up to 5 stories per the EIT guideline), ST samples are taken in the soft clay, and piles carry downdrag from the settling soil around them — Right: examples of district-level differences at Bang Phli, Bang Rak and the Thonburi side (typical area values, not design data)

Read more in Bangkok soft clay and foundation design, Negative Skin Friction in Bangkok and How many boreholes, and how deep

What real projects has SPN done in Bangkok and its vicinity?

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Table 1: Examples of SPN projects in Bangkok and its vicinity
AreaProject typeWork done
Central BangkokCondominiumSoil borings down to the bearing sand layer + SPT + Shelby tube sampling for high-rise pile design
Bang Phli, Samut PrakanDeep excavation along sheet pilesInstalled inclinometer casings to measure lateral soil movement throughout excavation
Sathon area, BangkokDowntown construction projectGPR underground scanning for pipes and buried objects before boring and pile driving
BangkokOld timber buildingGPR scanning for buried objects around an old building before renovation
Bangkok and vicinityRetaining wall on soft claySoil investigation and retaining wall design — see Case Study
BangkokUrban deep excavationExcavation performance monitoring system — see Deep excavation monitoring in Bangkok
SPN team installing an inclinometer casing beside a sheet pile line in a deep excavation, project in Bang Phli, Samut Prakan
Inclinometer installation beside a sheet pile line, project in Bang Phli, Samut Prakan — an area with especially thick upper soft clay, so deep excavations need movement monitoring throughout construction
SPN engineer scanning a downtown construction site with Ground Penetrating Radar in the Sathon area, Bangkok
GPR underground scanning on a project in the Sathon area — urban areas have dense buried pipes and utilities, and scanning before boring helps define safe locations

What does urban soil investigation need to manage in particular?

Work in Bangkok is constrained more by space and neighbors than by technical issues. Before mobilizing, SPN plans the following with the project owner:

  1. Access and rig area — the tripod rig and equipment truck need working space and soi access; for narrow sites, demountable equipment can be carried in through walkways.
  2. Drilling water and mud drainage — urban work must keep drilling water from flowing onto roads or into public drains.
  3. Noise, vibration and working hours — especially for pile testing and pile driving; adjacent buildings should be surveyed before work starts. Read Adjacent building survey and vibration monitoring
  4. Buried utilities — obtain drawings from the relevant agencies, or scan with GPR before setting borehole locations.
3D model of urban soil investigation in a narrow soi between shophouses 3D view of a narrow plot in a soi between two shophouses, cut away to show the soil layers on the front and right faces: fill, thick soft clay and stiff clay. On the plot, a demountable tripod rig stands on just a few square meters; a pickup truck parks against the edge of the soi with traffic cones. Drilling water flows into a mud sump and a storage tank and is not released into the public drain in front of the plot. Under the soi road run water pipes and electrical conduits, located with GPR before setting borehole locations, and the adjacent buildings have a condition survey and crack monitoring before work starts. Depth not to scale. 3D model — soil boring in a Bangkok soi Not to scale Soi access + rig area Demountable rig 1 Drill water: sump, tank Not into public drains 2 Adjacent building Pre-work condition/crack survey 3 Buried utilities GPR scan before siting holes 4 Depth compressed · Conceptual illustration
3D model — soil investigation in a soi between shophouses ① Soi access and rig area, using a demountable tripod rig ② Drilling water goes to a sump and storage tank, not into public drains ③ Condition survey of adjacent buildings before work starts ④ Pipes and cables under the soi road, located from drawings or GPR before setting borehole locations (depth not to scale)

How are prices and travel costs calculated in Bangkok and its vicinity?

Bangkok and its vicinity have SPN's lowest starting travel costs because they are within direct reach of our Bang Sao Thong office:

  • Soil investigation — 2–3 story houses start at approximately THB 20,000–40,000 (2–3 boreholes, 20–30 m deep, including basic lab tests and a report certified by an engineer). See Soil boring prices 2026 and Does a 2-story house need soil boring?
  • Pile testing — Seismic Integrity Test approx. THB 100–150/pile · Dynamic Load Test (PDA) from approx. THB 5,500/pile · Static Load Test THB 50,000–150,000+/pile. See Pile testing prices 2026
  • Travel cost — Bangkok and its vicinity are charged by actual distance, at the lowest starting rate compared with other regions.

The prices above are approximate starting prices and exclude travel and equipment mobilization, which are charged extra according to the distance to the site. Send the site coordinates and scope to receive a free quotation within 24 hours.

Summary

Bangkok and its vicinity are SPN's core area — from soil investigation for downtown condominiums to inclinometer installation for deep excavation in Bang Phli and GPR scanning in Sathon. Soft Bangkok clay means every project must bore down to the bearing sand layer and sample the soft clay properly, while district-level differences such as Bang Phli or Bang Rak underline that data from an adjacent plot cannot be substituted. The SPN team reaches sites fastest from our Samut Prakan office and delivers reports certified by a licensed engineer (COE license) that can be used for building permit applications. See starting prices and all service areas on the soil investigation service page

📌 Note

The soil layer thicknesses and borehole depths in this article are typical area values from the EIT guideline and field experience, not design data for any particular plot. Actual foundation design must be based on the project's own soil investigation results and is the responsibility of a licensed design engineer.