Soil Testing 101 | What Land Buyers Need to Know

What Land Buyers Need to Know Before Spending Money on Septic and Engineering

For many land buyers, soil testing feels like the moment where uncertainty finally turns into answers. Once the soil is tested, the thinking goes, you’ll know whether a property can be built and how to move forward.

In reality, soil testing is just one part of a larger due diligence process, and it’s often misunderstood, mistimed, or relied upon too heavily.

This article explains what soil testing does (and does not) tell you, when it makes sense to pursue it, and how experienced land buyers use early context to avoid spending money prematurely—particularly in markets like Northern Virginia and across Virginia, where septic outcomes can materially affect feasibility, cost, and design.

What Soil Testing Is (and Isn’t)

At its core, soil testing evaluates whether a property can support an onsite sewage system and, if so, what type.

What it can help determine:

Whether soils are suitable for wastewater absorption
The general type of septic system that may be required
Approximate placement constraints for drainfields

What it does not guarantee:

Final septic approval (while an Authorized Onsite Sewage Evaluator (AOSE) can prepare and submit a design for approval, final approval is issued by the local health department)
Construction cost certainty
Overall buildability of the site
That approvals will align with your intended home design

Soil testing answers technical questions, not strategic ones.

It’s also important to distinguish between septic certification and a septic construction permit. In Virginia, an approved septic certification generally does not expire, while a septic construction permit typically does. Buyers sometimes assume that a prior approval guarantees an easy path forward, without understanding whether permits are still valid or whether site conditions or regulations have changed since the original evaluation.

Why Septic Matters So Much for Land Buyers

For properties without access to public sewer, septic systems are not optional. They directly affect:

Whether a home can be built at all
How many bedrooms are permitted
Where the house, driveway, and other improvements can be placed
Cost, maintenance, and long-term usability

In Northern Virginia and across Virginia, onsite sewage system requirements are established at the state level by the Virginia Department of Health (VDH) and administered locally by county and regional health departments. While the regulatory framework is statewide, outcomes can vary meaningfully from site to site based on soils, setbacks, environmental features, prior approvals, and the interpretation of existing records.

Two similar-looking lots can have very different septic outcomes.

When Buyers Get Soil Testing Too Early

One of the most common land-buying mistakes is commissioning soil testing before understanding the broader risk context of a property.

This usually happens because:

Buyers want definitive answers quickly
Sellers suggest “just do a perc test”
Testing feels like progress

But soil testing is expensive, time-consuming, and conditional. If early red flags exist – related to access, zoning constraints, environmental overlays, or prior evaluations – testing may simply confirm problems that were foreseeable from the outset.

Experienced buyers want to know whether testing makes sense before paying for it.

What Can Often Be Learned Before New Testing

While new testing provides the most current data, meaningful insight often exists before any fieldwork begins.

Early review may uncover:

Prior health department records or applications
Historical soil evaluations or failed perc attempts
Environmental mapping indicating wetlands or buffers
Adjacent property outcomes that suggest risk

In many Virginia jurisdictions, health department archives and public records contain valuable context that buyers overlook, sometimes revealing why a property was never built on despite being marketed multiple times.

In some cases, understanding whether prior certifications exist – or whether permits have expired – can materially affect how a buyer approaches both testing and contract strategy.

This information doesn’t replace testing, but it can significantly change how buyers approach it.

Soil Testing Outcomes and Their Implications

Even when soils are technically suitable, results can introduce constraints buyers don’t anticipate.

Common outcomes include:

Approval for fewer bedrooms than expected
Requirement for alternative or engineered systems
Limited drainfield placement affecting site layout
Reduced flexibility for future expansion

In Northern Virginia, where lot sizes, setbacks, and environmental features often limit usable area, these outcomes can have outsized effects on design, cost, and long-term usability.

A “passing” result is not the same as a favorable one.

Why Soil Testing Alone Doesn’t Determine Buildability

It’s important to understand that soil testing evaluates one variable in a multi-variable decision.

Overall buildability is influenced by:

Zoning and land use regulations
Legal and practical access
Topography and grading feasibility
Environmental constraints
Market and economic alignment

Soil testing can confirm septic feasibility, but it cannot resolve conflicts between these factors. Buyers who rely on soil results alone often discover additional constraints later in the process—after time, money, or leverage has already been committed.

A Smarter Way to Approach Soil Testing

Experienced land buyers treat soil testing as a later-stage tool, not a starting point.

Before commissioning testing, they aim to understand:

Whether the site is worth deeper investment
What risks testing is intended to resolve
How different outcomes would affect their decision to proceed

This approach helps buyers avoid spending money to confirm problems they could have identified earlier and preserves leverage if a deal needs to be renegotiated or abandoned.

Considering a Land Purchase?

Soil testing is an important part of land due diligence, but it’s not the first step, and it doesn’t answer every question.

The Land Risk Review is a consulting-oriented, non-representation service designed to help buyers evaluating land in Northern Virginia and select Virginia markets understand early risk signals, identify potential septic and environmental concerns, and decide whether formal testing and engineering make sense before additional commitments are made.