The Soils Report Nobody Reads: What Is Under Your New Colorado Home

By Prerna Kapoor, CLHMS | REAL Brokerage | August 15, 2026

A buyer I was working with in Parker got the builder packet for her new build about two weeks before closing. It was thick. Warranty registration, HOA documents, appliance manuals, a paint schedule, and buried in the middle of it, a stapled report full of borehole logs and a table of numbers she had no idea how to read.

She asked me if any of it mattered. One document did. That stapled report is the reason her basement floor is built the way it is, and it is the single most useful page in the entire stack.

Colorado is one of the few states where the builder is legally required to hand you a soils report before you close. Almost nobody reads it. Here is what is in it and why it is worth twenty minutes of your evening.

The Report Is Required, and So Is the Timing

Under C.R.S. 6-6.5-101, every developer or builder selling a new residence has to give the purchaser a copy of a summary report of the soils analysis and the site recommendations at least fourteen days before closing. Not at closing. Not when you ask. Fourteen days before, so you actually have time to read it.

There is a second piece most buyers never notice. If the site has significant potential for expansive soils, the builder also has to give you a publication explaining what those soils do, how construction addresses them, and how you are supposed to care for the house afterward. In practice, that booklet is almost always the Colorado Geological Survey’s SP-43, A Guide to Swelling Soils for Colorado Homebuyers and Homeowners. If a builder handed you a small book about soil and you assumed it was marketing, it was not. It was a legal disclosure.

The penalty for skipping either one is a civil penalty of $500 payable to you. That is small enough that it is not much of a deterrent, which is exactly why you should ask for the report by name rather than waiting for it to appear.

The law does not apply to somebody building a house for themselves. It applies to builders and developers selling to a purchaser, which covers essentially every production and semi-custom home going up across the newer Parker subdivisions, Castle Rock, Aurora, and the rest of the metro right now.

What Is Actually In It

A geotechnical firm drills a set of test holes across the site, logs what comes out of each one, and runs lab tests on the samples. The report you get is the summary of that work. Four things in it are worth your attention.

The soil profile. How deep the topsoil goes, what sits underneath, and at what depth the drilling hit bedrock. Along the Front Range, that bedrock is frequently claystone, and claystone is the whole reason this document exists.

The swell test results. A sample gets wetted under load and the lab measures how much it expands and how hard it pushes back. You will see a percent swell figure and a swell pressure figure in pounds per square foot. The report will then sort the site into a category, usually something like low, moderate, high, or very high expansive potential. Different firms use slightly different cutoffs, so read the classification the report itself gives rather than comparing raw numbers to something you found online.

Groundwater. Whether water was found in the borings, at what depth, and whether the report recommends a perimeter drain or a sump. If you are planning to finish the basement later, this paragraph is the one that decides how that project goes.

The recommendations. Foundation type, floor system, how far to keep irrigation from the house, what slope to hold away from the foundation. This is the part that translates into how your house was built and what you are responsible for maintaining.

Swelling soils are not a niche Colorado problem. The Colorado Geological Survey has documented for years that they cause more cumulative property damage in this state than the natural hazards people actually worry about. It is a slow hazard, which is why it does not make the news, and it is why we have a disclosure statute for it and not for much else.

Structural Floor or Slab on Grade

If you read one line in the recommendations, read this one.

A slab on grade basement floor is concrete poured on compacted fill or gravel, resting on the ground. It is the standard approach, it costs less, and on stable soil it is completely fine.

A structural floor does not rest on the ground at all. It spans between foundation walls and piers with an air gap, a void, underneath it. The soil can swell into that gap and the floor above it does not move. Depending on the builder you may see this as concrete on a void form, or as a wood-framed floor over a crawl space.

On a lot with high swell potential, that gap is what stands between the soil and your finished basement. A conventional slab on the same lot can lift, crack, and push interior partition walls up into the ceiling over a period of years.

Two practical things follow from this. First, a structural floor is typically a meaningful upgrade cost, and on many builder contracts it appears as an option rather than as standard construction. If the report recommends one and the base plan does not include one, that is a conversation to have before you sign, not after. Second, if you are buying a resale rather than a new build, the same question still applies to whatever is under that house, and a general inspection will not answer it. That is a structural engineer’s call. I walked through how that fits into the rest of a Colorado inspection in what Colorado homeowners should know about their foundation.

Ask Whether It Is Your Lot or the Subdivision

Here is the distinction that catches people, and it is the thing I ask about on every new build I represent.

Developers usually commission a subdivision-wide geotechnical study early, with borings spread across the whole filing. Individual lots then get an open-hole observation when the excavation is dug, and sometimes a lot-specific report on top of that.

Those are not the same document. A subdivision study tells you what the geology tends to do across sixty lots. Your lot is one of them, and soil conditions on the Front Range can change substantially within a couple hundred feet, particularly where a filing crosses an old drainage or where a lot sits on deep engineered fill rather than native ground.

So ask two questions in writing. Is there a lot-specific soils report or open-hole observation for my address, and can I have a copy? And was the foundation built to the recommendation in that document?

Most builders answer both without much friction. The answer becomes part of your file, which matters later, because a warranty claim about a moving floor goes very differently when you can point to what the engineer recommended. Structural coverage is usually the longest-running piece of a builder warranty and the hardest to collect on, which I got into in how new construction warranties actually work in Colorado.

The Part That Is On You After You Move In

Expansive soil only misbehaves when the moisture around it changes. Which means a large share of the outcome is in how you water your yard, and the report will tell you this in dry engineering language that is easy to skim past.

The recommendations you will see, in some version, on nearly every Front Range report:

Keep the ground sloping away from the foundation for the first ten feet, usually something close to a six-inch drop. Extend downspouts well clear of the backfill instead of letting them dump at the corner of the house. Keep sprinkler heads and drip lines back from the foundation, commonly five feet or more. Do not plant thirsty landscaping right against the wall. And keep watering steady rather than swinging between drought and soaking, because it is the swing that does the damage.

This is also where the new-build years get people. Backfill settles for the first several seasons, and a grade that drained correctly at closing can go flat or start pitching back toward the house by year three. Walk your perimeter after a hard rain each spring. Water standing against the foundation is the cheapest problem you will ever fix and one of the most expensive to ignore.

One more thing worth knowing before you plan a basement finish. If the report flagged a high swell potential or shallow groundwater, that changes how you frame, whether you float the walls off the slab, and how you handle the floor covering. It is not a reason to skip finishing the space, and finished square footage below grade does real work for resale, as I covered in what a finished basement is worth in Colorado. It is a reason to hand the report to your contractor before they bid it.

Quick answers

When is my builder required to give me the soils report?

At least fourteen days before closing, under C.R.S. 6-6.5-101. The builder has to provide a summary of the soils analysis and the site recommendations, and where expansive soils are a significant concern, a publication explaining them as well. A builder who does not provide it owes you a $500 civil penalty, though the more useful move is simply to request it by name early rather than to collect the penalty later.

What is the difference between a structural floor and a slab on grade?

A slab on grade sits directly on the ground, so it moves when the soil beneath it moves. A structural floor spans between foundation supports with a void underneath, so expanding soil has somewhere to go without lifting the floor. On lots with high swell potential a structural floor is the standard engineering answer, and it is often priced as an upgrade on builder contracts rather than included.

Does the soils report cover my specific lot?

Sometimes, and sometimes not. Many builders provide a subdivision-wide study, with a separate open-hole observation done at your lot during excavation. Conditions can vary a lot within a single filing, so ask in writing whether a lot-specific report or observation exists for your address, request a copy, and confirm the foundation was built to what it recommended.

Is expansive soil a reason not to buy in Douglas County?

No. It is a reason to read the report and to keep your drainage and irrigation right for as long as you own the house. Thousands of homes across Parker, Castle Rock, and Highlands Ranch sit on these soils and perform fine for decades, because they were engineered for the conditions and maintained sensibly. The problems tend to show up where the construction ignored the recommendation or the grading was allowed to fall apart.

If you are under contract on a new build and you want a second set of eyes on the soils report before your fourteen days run out, send it to me. I will tell you what it says in plain language and what to ask your builder. No pitch, no obligation. If you are earlier than that and still sorting through how Colorado transactions work generally, the Colorado real estate FAQ covers a lot of the groundwork.

Prerna Kapoor | REALTOR® | Luxury Home Specialist
REAL Brokerage | 720-949-5450 | info@prernakapoor.com
CLHMS • RENE • PSA • ABR | International Sterling Society Award Winner

Prerna specializes in residential real estate across Parker, Aurora, Lone Tree, Castle Pines,
Highlands Ranch, Cherry Creek, Greenwood Village, and Centennial. She speaks English, Japanese,
and Hindi.