Structural Foundation Elements for Pools in DFW
North Texas homeowners often hear horror stories of pools cracking or shifting due to the region’s notorious expansive clay soils. This section explains when and why you might need special foundation supports (beneath the gunite pool shell) to combat problematic soil conditions. We’ll cover what expansive clay can do to pools, how to know if you need a geotechnical or structural engineer, and key support methods like piers, grade beams, void forms, soil stabilization injections, and drainage. All which can keep your pool structurally sound. By understanding these measures, you’ll feel confident asking your builder or engineer about extra support systems when appropriate.
Disclaimer: Always consult with a licensed engineer in the state of Texas. The following information reflects the professional opinions of the Radelli Designs team and is not a substitute for a formal geotechnical analysis or the direction of a licensed structural engineer.
(Sub-Shell Support Systems)
When clay soil moisture changes, the ground can heave upward or settle unevenly. A gunite (concrete) pool shell set in such soil may experience stresses that lead to:
Cracks in the pool shell or tile – swelling soil can squeeze the pool walls laterally and even crack the gunite . As little as a fraction of an inch of differential movement can cause a structural crack.
Pool out-of-level or lifted - one side of the pool may lift or sink, resulting in a visibly uneven waterline . Expanding soils beneath the pool can literally push sections of the shell upward.
Deck and coping movement – the concrete deck can heave or separate from the pool coping. You might see the mastic joint between deck and coping open up or the deck lifted into a “toe stub” trip hazard .
Plumbing breaks – pipes and fittings can shear or leak due to the ground shifting . Soil movement puts strain on underground plumbing lines.
Other misalignments – features like skimmers, spa spillways, or waterfalls can get out of alignment and stop working properly if the pool settles or tilts .
Expansive Clay Soils in North Texas and Pool Stability
In short, without special precautions, expansive clay can compromise a pool’s structural integrity, causing leaks, damage to surrounding patios, and expensive repairs . These problems often compound over time: for example, once a crack forms and the pool leaks, the added water in the soil causes further swelling, which can heave the pool even more . It’s a vicious cycle that proactive engineering can help maybe prevent.
Expansive clay soil in North Texas showing deep shrinkage cracks during a dry spell – this soil will swell dramatically when rehydrated, causing ground uplift. North Texas (especially the DFW area) is well known for heavy clay soils that swell when wet and shrink when dry, leading to significant ground movement . In fact, local soil reports have measured potential vertical “heave” (uplift) of up to 7+ inches in some DFW locations – an astonishing amount of movement! This soil expansion and contraction can wreak havoc on an in-ground pool shell and deck, which are typically rigid structures.
When to Get a Geotechnical or Structural Engineer Involved
Not every pool requires an advanced foundation, but in many North Texas areas it’s wise to consult experts early. If it were up to us every pool should get a geotech analysis but we definitely understand that sometimes it just isn’t feasible. Here are some situations when a homeowner should consider asking for a soils analysis or structural review before pool construction:
Evidence of Clay or Unstable Soil on Site: If your yard exhibits deep drying cracks in summer or gummy, sticky mud when wet, you likely have expansive clay soil . Large ground cracks during dry spells are a red flag . These signs indicate you should get a professional soil evaluation.
Known Expansive Soil Zone: Much of North Texas has clay, if neighbors or the neighborhood have had foundation repairs, or if your home’s foundation was built with piers due to soil, assume your pool will face similar soil challenges. In such cases, it’s not overkill to involve an engineer.
Prior Foundation or Drainage Issues: If your house or driveway has experienced settling or cracks from soil movement, or if your yard has drainage problems (standing water or runoff toward where the pool will go), definitely discuss soil support options. Past issues suggest the soil needs special attention.
Large or High-Investment Pool Projects: For more complex builds – e.g. a big pool, negative-edge (infinity) designs on a slope, pools with heavy rock features/waterfalls, or a pool very near the home foundation – the stakes are higher. Engaging a geotechnical engineer to test the soil and a structural engineer to design a suitable support system can protect your substantial investment.
Builder Recommendation or Uncertainty: A reputable pool builder familiar with local soils may suggest getting a geotechnical report or adding piers/injections. If your builder has not mentioned soil testing and you have any reason to suspect clay, it’s wise to bring it up yourself. Many pool builders unfortunately skip geotechnical analysis to save cost, or they downplay soil risk (“we’ve always done it this way”) . As the homeowner, you have the right to insist on proper due diligence.
Pro Tip: If the roads in your neighborhood are cracked, crumbling, or feel like a rollercoaster ride, chances are you're living on expansive or unstable soil. This type of ground can impact everything from your foundation to your future pool project.
Soil Types In Denton, Collin & Dallas County
Windhurst-Chaney-Duffau
Gasil-Crosstell-Callisburg
Brackett-Purves-Real
Aledo-Sanger-Bolar
What does a geotechnical/ structural review involve?
Typically, a geotechnical engineer can perform one or more soil borings in your yard and laboratory tests to determine the soil profile (clay content, moisture, density, plasticity index which measures expansion potential, etc.). They will identify how deep the active clay layer goes (often the top several feet move the most ) and may find a stable strata (like bedrock or dense soil) below. The geotech report will then recommend foundation solutions for the pool (For your structural engineer to review), whether piers are needed and how deep, or if chemical stabilization is advised, etc. . A structural engineer (often working with the pool builder or provided with the soil data) can then design the pool shell and any sub-shell supports accordingly. While a soil report and custom engineering do add upfront cost (in Texas, a residential geotech report might range from a few hundred up to a few thousand dollars, depending on scope), this is nominal compared to the cost of repairing a failed pool structure. As the saying goes, “an ounce of prevention equals a pound of cure.” A tailored engineering plan based on your soil can prevent nightmares like major reconstruction, legal disputes, or an unusable pool down the road.
What Is Typically Included in a Geotechnical Analysis for Pool Construction in North Texas?
Bottom line: If you suspect problematic soil or your builder does not seem to be accounting for it, proactively ask for a geotechnical evaluation. It will either give peace of mind that standard construction is fine, or it will arm you with the data to justify necessary enhancements (before the pool is built). In clayheavy regions, this step is as crucial as proper steel rebar in the concrete