Foundation Design Based on Sondir Test Results in Lombok

Foundation Design Based on Sondir Test Results in Lombok (2026 Guide)

After completing soil investigation with Sondir (Cone Penetration Test), the next step is translating those results into a safe and compliant foundation design. This article explains how sondir data influences foundation choices, practical considerations for Lombok’s terrain, and related material costs for budgeting.

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Why Foundation Design Depends on Sondir Data

Sondir testing provides:

• Bearing Capacity: Determines allowable load per square meter.
• Soil Layer Profile: Identifies depth of hard strata and weak zones.
• Groundwater Level: Influences waterproofing and excavation planning.

Without this data, foundation design becomes guesswork, increasing risks of settlement, cracking, and compliance delays.

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Common Foundation Types in Lombok

1. Shallow Foundations

Used when sondir shows firm soil within 1–2 meters.

• Footings and Tie Beams: Suitable for villas and low-rise structures.
• Material references:
• Ready Mix Concrete: Rp 1,232,435 per m³
• Reinforcing Steel Ulir: Rp 17,255 per kg
• Besi Beton Ø12 mm: Rp 166,914 per pcs
• Formwork Timber Beam: Rp 1,704,344 per m³

2. Deep Foundations

Required when sondir indicates weak soil near the surface.

• Bored Piles or Driven Piles: Transfers load to deeper strata.
• Material references:
• Steel Reinforcement for Piles: Rp 16,217–17,255 per kg
• Concrete for Pile Casting: Rp 1,232,435 per m³
• Casing Pipe (GI): Rp 336,000 per meter (Ø2")

3. Raft Foundation

Used for large footprints where soil bearing capacity is moderate.

• Material references:
• Concrete Volume: Higher than isolated footings.
• Steel Mesh and Rebar: Rp 16,217–17,255 per kg
• Formwork Plywood: Rp 215,103 per sheet (12 mm)

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Practical Steps After Sondir Testing

1. Interpret Data with Structural Engineer
2. Use cone resistance values to calculate allowable bearing pressure.
3. Identify depth for footing or pile termination.
4. Adjust Design for Groundwater
5. If water table is high, include sump pits and waterproofing membranes.
6. Consider PVC drainage lines (Ø4" at Rp 150,965 per meter) to manage seepage.
7. Plan Excavation and Backfill
8. Use Selected Fill Soil (Rp 227,028 per m³) for leveling and compaction.
9. Compact in layers and verify density before pouring concrete.
10. Document for Compliance
11. Attach sondir report and foundation drawings to OSS and PBG submissions.
12. Inspectors will check alignment between soil data and structural design.

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Related Material Costs for Budgeting (Indicative 2025)

| Item | Unit | Price (Rp) |

| ---------------------- | ----- | ---------- |

| Ready Mix Concrete | m³ | 1,232,435 |

| Reinforcing Steel Ulir | kg | 17,255 |

| Besi Beton Ø12 mm | pcs | 166,914 |

| Formwork Timber Beam | m³ | 1,704,344 |

| PVC Pipe AW Ø4" | meter | 389,000 |

| Selected Fill Soil | m³ | 227,028 |

| Plywood 12 mm | sheet | 215,103 |

(Prices are indicative as of 2025 and vary by location and logistics.)

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Compliance and Risk Management

Indonesian building regulations require geotechnical data for structural permits. Aligning foundation design with sondir results ensures:

• Reduced risk of structural failure.
• Faster PBG approval and SLF issuance.
• Lower long-term maintenance costs.

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Pricing Disclaimer (2025)

All prices listed are indicative as of 2025 for Central Lombok. Actual costs vary by location, supplier stock, and logistics from Java/Bali. Remote sites or urgent schedules may increase costs. Always confirm current rates and specifications before procurement.

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Summary

Foundation design based on sondir results is a critical step for villas, resorts, and commercial buildings in Lombok. By integrating soil data into structural planning and budgeting for related materials, investors can achieve safe, compliant, and cost-effective construction.

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