Testing and Inspections

Understand what needs to be tested on your site and why it matters before building begins

Why Site Testing Matters

Before construction can move forward, you need to know what’s under your site. Even a flat, open lot can have soil instability, drainage problems, or other conditions that affect how (or if) you can build. Site testing helps you uncover those issues early, so they can be solved during design, not discovered during construction.

Some tests are required by the city, others by your engineer or builder, and a few are just smart to do before committing to a design. Together, these assessments give your team the information they need to make safe, legal, and cost-aware decisions.

What These Tests Help With

• Confirm the site is buildable and safe for structures
• Identify soil or slope conditions that affect foundation design
• Determine septic feasibility if no sewer connection is available
• Flag drainage or environmental concerns
• Meet code requirements for permitting and energy efficiency
• Prevent delays from costly surprises once construction begins

Common Types of Testing and Inspections

Soil Testing (Geotechnical Report)

This test evaluates how stable and strong your soil is, how deep bedrock or water might be, and whether the ground can support your project. The engineer uses the results to design a safe foundation.
When it’s required: New construction, hillside lots, unknown soil conditions, or complex foundations.
Who performs it: Licensed geotechnical engineers.

Soil Boring and Sampling

Crews drill into the ground to collect deeper soil samples. These are used to analyze changes in soil type, moisture levels, and compaction across different depths.
When it’s required: Sites with questionable fill, poor documentation, or groundwater risks.
Who performs it: Drilling teams or labs under the supervision of a geotechnical engineer.

Perc Test (Percolation Test)

A basic drainage test that checks how fast water drains through the soil. This determines if your site is suitable for a septic system.
When it’s required: Any project relying on septic instead of city sewer.
Who performs it: Septic designers, civil engineers, or soil evaluators approved by the county health department.

Compaction Test

Verifies whether soil that’s been added or graded has been compacted enough to build on. Poor compaction leads to settling and structural problems.
When it’s required: After grading or filling the lot, and before concrete is poured.
Who performs it: Soils technicians or special inspection teams.

Slope Stability / Slope Failure Analysis

This test assesses whether a sloped lot is prone to erosion, shifting, or landslides, and what type of foundation or retaining systems are needed.
When it’s required: Steep lots, known hillside movement areas, or coastal/cliffside locations.
Who performs it: Geotechnical engineers.

Blower Door Test / Duct Leakage Test

These energy performance tests measure how airtight your home is, and how efficient the HVAC duct system is. They’re part of most modern energy codes.
When it’s required: New construction or major remodels that affect insulation, ducts, or the building envelope.
Who performs it: Certified HERS raters or energy consultants.

Asbestos / Lead / Mold Testing

Old buildings may contain hazardous materials that must be identified and removed safely before demolition or renovation.
When it’s required: Homes built before 1980 (asbestos) or 1978 (lead), or when mold or water damage is present.
Who performs it: Certified environmental consultants or industrial hygienists.

Septic Suitability Evaluation

This broader evaluation looks at soil, slope, setbacks, and drainage to determine whether a septic system will be allowed, and where it can go.
When it’s required: Rural lots without sewer, new builds using septic, or ADUs on lots with existing systems.
Who performs it: Septic designers, soil engineers, or county-licensed site evaluators.

When Testing Is Required

Some tests are triggered by code, others by the design process. Testing is usually required when:

• You’re building on raw land or sloped terrain
• Your site needs a septic system
• You’re demolishing or remodeling a home built before 1980
• You’re near a fault line, in a flood zone, or in a fire-prone area
• Your architect or engineer requests soil data to complete structural or grading plans

Always ask your team which tests you’ll need based on your location and scope.

Who Performs the Testing

Your architect, contractor, or civil engineer may help coordinate testing and refer you to reliable specialists.

What Happens With the Results

Once testing is complete, your design and engineering teams use the data to:

• Finalize structural design (foundations, retaining walls, drainage)
• Complete grading or civil engineering plans
• Update site layouts based on feasibility
• Submit documentation to the city or county as part of the permit package
• Adjust budget expectations if unexpected challenges arise

In some cases, testing leads to redesigns or mitigation plans, but it’s always better to catch those issues early.

What’s Next: Engineering Types and Definitions

Now that site conditions are better understood through testing and inspections, the next step is understanding how engineers use that information to support design, safety, and permitting. Different types of engineers are involved in various parts of a project depending on its complexity, location, and scope.

Continue to Engineering: Types and Definitions to learn the roles of structural, civil, MEP, and geotechnical engineers, and when each may be needed on your project.