When Do You Need a Soil Report for a Pool or Backyard Project?

Soil Reports: The Foundation of Your Project

The dirt under your backyard determines a lot about what you can build and how much it costs. A soil report—officially called a geotechnical investigation—tells us what we're working with before we design anything. In Los Angeles, these reports are sometimes required and always informative.

When Soil Reports Are Required

LADBS requires soil reports for:

• All hillside properties (designated hillside zones)
• Properties with known geological hazards
• Retaining walls over 4 feet high
• Projects requiring caissons or deep foundations
• Some grading permits over certain quantities

When They're Recommended But Not Required

• Pools in areas with expansive clay soils (common in LA)
• Properties near hillsides or former fill areas
• Projects where water table is a concern
• Large hardscape installations with concrete
• When you've seen cracking in existing concrete or structures

What's in a Soil Report

A typical geotechnical investigation includes:

• Soil boring (drilling to collect samples)
• Laboratory analysis of soil properties
• Bearing capacity determination
• Expansion index (how much soil swells with moisture)
• Recommendations for foundations and footings
• Groundwater observations

The report tells engineers how to design foundations. Expansive soil? You need special footings. High water table? Drainage becomes critical. Poor bearing capacity? Deeper piers or caissons may be needed.

Soil Report Costs in Los Angeles

Expect to pay:

• Basic report (1-2 borings): $1,500-$2,000
• Standard report (3-4 borings): $2,000-$3,000
• Comprehensive hillside report: $3,000-$5,000
• Reports with geology component: $4,000-$6,000

The cost depends on number of borings, depth required, and whether geology mapping is included.

Common Soil Issues in Los Angeles

Expansive Soils

Much of LA has clay soils that expand when wet and shrink when dry. This movement cracks concrete, pool shells, and foundations. Mitigation includes deeper footings, flexible joints, and proper drainage.

Fill Soil

Some properties sit on fill—soil that was brought in rather than natural. Fill can settle unpredictably. Building on fill often requires compaction testing or deep foundations to native soil.

High Water Table

Areas near the coast, rivers, or former wetlands may have shallow groundwater. Pools in high water table areas need special drainage systems to prevent popping (yes, pools can float out of the ground).

The Process

Getting a soil report typically takes:

1. Schedule the geotechnical engineer (1-2 weeks out)
2. Site visit and drilling (half day)
3. Laboratory testing (1-2 weeks)
4. Report preparation (1 week)
5. Total timeline: 3-4 weeks

Plan for this early in your project. You need the report before structural engineering can be completed.

The soil report found expansive clay that would have cracked our pool. Extra cost upfront saved us from major problems later. — David K.