How a factory investor should read a soil investigation report: an engineer's 8-point guide
The soil investigation (geotechnical) report is the invisible but most expensive component of a factory investment. Misreading it determines the foundation design, machine layout and post-liquefaction risk. Eight critical points for non-engineer investors.
Abdulbaki Yetis
Environmental Engineer | Real Estate Advisor
A soil report is not paperwork; it is the foundation of the investment. When read poorly, the land cost looks small while excavation and improvement costs grow large.
1. Are the borehole count and depth sufficient?
For factories — wide-footprint structures — the borehole count and depth differ from those of a residential building. A report with only one or two boreholes is usually insufficient. Depending on site area, machinery loads and foundation type, 5-15 boreholes at 15-30 m depth is the standard range.
Insufficient sampling hides intra-parcel variability. A spot that looks fine in one borehole can be soft where a machine ends up sitting, generating expensive foundation rework or ground improvement.
2. Interpreting SPT, CPT and observation values
Standard Penetration Test (SPT) and Cone Penetration Test (CPT) describe soil density and strength. Layers with SPT N30 below 10 deserve careful liquefaction screening. The groundwater level must also be on the report.
3. Groundwater level and drainage
Parcels with shallow groundwater drive up basement, drainage and retaining-wall costs. In parts of the Marmara corridor the water table sits 1-2 m below surface. For an industrial facility this can require ground improvement, retaining-wall grouting and continuous pumping — all line items absent from the initial budget.
4. Liquefaction risk — especially in Marmara
Near the Marmara fault liquefaction risk can be high. Does the report include a liquefaction analysis? Which method was used (Seed-Idriss, Boulanger-Idriss)? At what critical depth? A report that cannot answer these is incomplete.
Where liquefaction is identified, jet grouting, pile foundations or ground improvement become mandatory. These items add 200-1500 TL per m² to the foundation cost; for a full factory that scales into millions.
5. Swell and settlement behavior
Some clay layers swell or settle unevenly. In a manufacturing facility this directly affects machine placement; precision tooling has settlement tolerances. The report should include consolidation parameters and long-term settlement calculation.
6. Seismic regulation and soil class
Under the Turkish Building Earthquake Code 2018 the soil class is determined (ZA, ZB, ZC, ZD, ZE). ZE soils significantly increase foundation cost and time. The investor must see this classification in the report.
7. Excavation volume and cut-fill cost
The parcel topography and the planned building elevation determine excavation volume. Hauling and disposal costs per m³ vary with distance and waste type. Can the soil from the report be reused as fill, or must it go to a licensed site?
8. Recommended foundation type and cost impact
At the end of the report the geotechnical engineer recommends a foundation type: shallow (raft), piled or shallow after ground improvement. This recommendation drives a 300-1000 TL per m² spread in foundation cost between options.
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Author
Abdulbaki Yetis
Environmental Engineer · Founder, Lizaz Emlak
Roughly 15 years of industrial-construction site experience. Active assignments at DP World Yarimca port projects, Yildiz Demir Celik steel facility, the Tezcan Galvaniz plant and Symbol Kocaeli shopping mall + hotel + hospital mixed-use project. Reads real estate not as a listing, but as an engineering problem at the intersection of zoning, operations, infrastructure/environment and financing.
Practice areas: industrial real estate · factory and warehouse feasibility · OSB vs. off-OSB investment comparison · residential land and urban transformation · EIA and environmental permit assessment · strategic site selection across the Marmara corridor.
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