Gulf Coast Homesite Due Diligence

What Is a Geotechnical Soil Test?

A buyer and seller’s guide to waterfront homesites on Ono Island, in Orange Beach and along the Gulf Coast.

When buyers begin looking at a beautiful waterfront homesite, it is perfectly natural to focus on what can be seen: the view, the shoreline, the boating access, the trees and the possibilities for a future home.

But one of the most important parts of the property may be the part no one can see.

The soil beneath a coastal lot can influence how a house must be supported, how deep foundation pilings may need to extend and, ultimately, how much the project may cost. That is why I often encourage buyers considering waterfront land—especially property containing wetlands or lower-lying areas—to learn about geotechnical testing during the due-diligence period.

A geotechnical investigation is not the same as a wetland delineation, survey or environmental study. It answers a different but equally important question.

As an Ono Island homeowner and a full-time real estate advisor, I believe the best land purchases are made by looking beyond the view and understanding the property from the waterline all the way down to the supporting soil.

Below the Surface

What is a geotechnical investigation?

A geotechnical investigation evaluates subsurface soil and groundwater conditions in the area where a structure is proposed.

For a coastal residential project, an engineering company may perform soil borings, Cone Penetration Testing—commonly called CPT—or another form of subsurface exploration. The exact method depends on the site, the proposed construction and the engineer’s recommended scope.

During CPT testing, specialized equipment pushes an electronic cone into the ground at a controlled rate. The cone records measurements such as resistance at its tip, friction along its sleeve and pore pressure. A geotechnical engineer interprets that information to develop a continuous profile of the soil layers below the proposed structure.

The completed report may include recommendations concerning:

• Site grading and building-pad preparation
• Removal or treatment of unsuitable material
• Foundation design considerations
• Potential settlement concerns
• Piling or deep-foundation considerations
• Construction practices related to the soil conditions encountered

The report is then used by the structural engineer, architect and builder when planning the home’s foundation. It does not replace structural engineering, but it gives the design team site-specific information instead of asking them to rely on assumptions.

Coastal Construction

Why can this matter so much on a waterfront lot?

Coastal soils are not always uniform. A homesite can look dry and firm at the surface while containing softer, looser, organic or more compressible material below. Conditions may also vary from one side of a parcel to the other.

That variation matters when the buyer is contemplating an elevated coastal home or a pile-supported house.

If suitable supporting soil is located at a reasonable depth, the results may give the buyer and design team greater confidence as they move forward. If weak soil extends considerably deeper than expected, the project could require longer pilings, a different piling system, additional engineering or more extensive site preparation.

Those requirements may be entirely manageable—but they belong in the construction budget.

Value on Both Sides

How the information helps buyers and sellers

The investigation does not provide a guaranteed foundation price, and it does not independently certify that a property is buildable. Final cost depends on the house design, elevation, structural loads, piling type, contractor pricing, access and permitting requirements.

A seller should also be careful not to promise that a particular house can be built for a particular price. Reports may be limited to a specific client, structure location and intended use. If a seller commissioned the report, a buyer may need written permission or a reliance letter before relying upon it.

An Important Distinction

Is geotechnical testing the same as a wetland delineation?

No. This is one of the most important distinctions for Gulf Coast land buyers.

The U.S. Army Corps of Engineers explains that a delineation identifies and locates aquatic resources, while a jurisdictional determination addresses whether those resources are regulated under applicable federal authority. These are related concepts, but they are not necessarily the same deliverable.

Finding wet soil or groundwater during geotechnical testing does not, by itself, establish a wetland boundary. Likewise, a wetland delineation does not tell a structural engineer how deep the home’s pilings should extend.

A Clearer Picture

Four reports buyers often confuse

Each professional answers a different question. Together, their work begins to create a much clearer picture of the property.

From Possibility to Plan

A thoughtful waterfront-lot due-diligence sequence

Every property is different, but I generally like the process to move from identifying the available building area to testing the location where the home is actually expected to sit.

1. Review zoning, setbacks, community requirements, flood information and available records.
2. Order a current boundary and topographic survey.
3. Complete a wetland delineation when wetlands may be present.
4. Have the wetland flags and other relevant features located on the survey.
5. Develop a preliminary site plan or clearly mark the proposed house footprint.
6. Perform geotechnical testing within that proposed footprint.
7. Have the structural engineer and builder review the geotechnical recommendations.
8. Obtain preliminary guidance concerning foundation, site-work and access costs.

Before Authorizing the Work

Questions I would ask the geotechnical engineer

• How many CPT soundings or borings are included?
• How deep will the testing extend?
• Is there a maximum amount of testing included in the quoted fee?
• What will deeper or additional testing cost?
• Will the report address a pile-supported residence?
• Will groundwater observations be included, and what do they represent?
• Does the scope cover only the house or also other proposed structures?
• What type of equipment will enter the property?
• Will clearing or difficult access create additional costs?
• Has access been coordinated to avoid unnecessary wetland disturbance?
• Who may rely upon the final report?
• What happens if the proposed house footprint changes?

I also recommend giving the engineer as much accurate project information as possible. The approximate house location, number of stories, construction type, first-floor elevation and anticipated foundation system can all help define the assignment.

The Larger Feasibility Picture

Does a favorable soil report prove that the lot is buildable?

No single report proves overall buildability.

A favorable geotechnical report addresses only part of the feasibility picture. A buyer must also consider wetlands, zoning, setbacks, floodplain requirements, survey matters, community architectural standards, access, utilities, drainage, permitting, dock or shoreline requirements and the proposed home design.

On Ono Island, additional community requirements and architectural-review considerations may apply. In Orange Beach and other coastal jurisdictions, the appropriate local and regulatory authorities should be consulted for property-specific requirements.

This is why I encourage buyers to assemble a team rather than rely on one opinion. A qualified surveyor, wetland consultant, geotechnical engineer, civil engineer, structural engineer, architect, builder and appropriate permitting authorities may each have an important role.

Meredith’s Perspective

A gorgeous view can inspire the purchase. Good information helps protect it.

I love helping buyers discover waterfront homesites where the view, boating access and future home can come together beautifully. But I also believe that the most exciting possibilities deserve careful due diligence.

For buyers, geotechnical testing may reveal important foundation considerations before construction plans are too far along. For sellers, having appropriate professional reports may make a unique homesite easier for serious buyers to evaluate. For both sides, the goal is greater clarity—not a false promise that every uncertainty has disappeared.

If you are considering buying or selling a waterfront homesite on Ono Island, in Orange Beach or elsewhere along the Gulf Coast, I would be glad to help you think through the real estate side of due diligence and connect the questions that should be addressed by the appropriate local professionals.

Explore Gulf Coast homes and land for sale by waterway, learn more about building along the Gulf Coast, or visit SearchTheGulf.com, the Gulf Coast’s premier website for searching real estate listings.

Ask Meredith a Question

This article is intended for general real estate education and is not engineering, environmental, surveying, legal or permitting advice. Property-specific questions should be directed to appropriately licensed professionals and applicable authorities.