What Is Under a Court: Subgrade, Base and Why They Decide the Lifespan
Sport court base construction is the part of the job nobody photographs and everybody pays for twice when it is done badly. Buyers choose a color. They compare surface systems. Then the court is finished, the pretty layer is on top, and every question about how long it lasts has already been answered by material nobody will ever see again.
Some of the courts we built decades ago are still flat and still in service. The surface on those has been redone more than once, which is normal. The structure under them has never been touched, which is the entire point.
The stack, bottom to top
A hard court is a layered system. Each layer has one job and depends completely on the one below it.
- Native subgrade. The existing soil, cut or filled to a designed elevation, moisture conditioned and compacted.
- Aggregate base. A graded crushed rock layer that spreads load and provides a working platform.
- The slab. Concrete in most of the Southwest, reinforced and jointed.
- Surface system. Acrylic color coatings, or a modular tile system, or synthetic turf depending on the sport.
The failure mode people expect is the top layer wearing out. That does happen, and it is normal maintenance. The failure that ends a court’s life starts at the bottom.
Subgrade: the layer nobody photographs
Subgrade work is unglamorous and it is where the lifespan is decided.
First, strip everything that is not soil. Topsoil, roots, buried irrigation, old landscape fabric, construction debris. Organic material decomposes and leaves a void. Anything that can rot or settle has to leave the site.
Second, get the moisture right. This is the step most often skipped in the desert. Soil compacts properly only within a narrow band around its optimum moisture content, and native soil here is usually far drier than that. Running a roller over dry soil produces a surface that looks compacted and is not. Water has to be added, mixed in, and given time to distribute through the lift before compaction means anything.
Third, compact in controlled lifts and verify. Compaction is specified as a percentage of maximum dry density determined by a Proctor test, and it is verified in the field with a density gauge or sand cone. Ask whether your project has a compaction specification and whether anyone is testing to it. On a residential job the honest answer is frequently no, and that is a choice worth making deliberately rather than by default.
Fourth, proof roll. Drive a loaded vehicle across the finished subgrade and watch. Anything that pumps, ruts or springs under the tire is a soft spot, and it needs to be over-excavated and replaced with compacted material rather than bridged over and hoped about.
A geotechnical report is not required on most residential courts, but it earns its keep on sites with known expansive clay, deep uncontrolled fill, a high water table, or a history of movement in nearby structures. If your house has foundation history, your court will have foundation history.
The aggregate base
The base layer spreads concentrated load across the subgrade and gives the crew a stable platform to build on. Two things matter: the material and the compaction.
Material means a graded crushed aggregate with a specified gradation, not whatever the nearest yard is selling as fill. A well graded base has a distribution of particle sizes that lock together under compaction. Uniform round material does not lock, and material with too many fines holds water and behaves like soil.
Thickness is a design decision driven by subgrade strength, expected loading and the slab above. There is no single correct number, and anyone who quotes one without asking about your soil is reciting rather than designing.
A geotextile separation fabric between subgrade and base costs very little and does something specific: it stops fine soil particles from migrating up into the base under repeated wetting and loading. Without it, the base slowly becomes contaminated, loses its drainage capacity and stops behaving like a base. This is one of the first line items to disappear when a bid is being sharpened, and it is one of the reasons we wrote about cutting corners on a sport court.
The slab
Most courts in Southern Nevada and Arizona are concrete. Concrete tolerates heat better than asphalt, holds its plane longer, and is a better substrate for acrylic surfacing over the long run.
Reinforcement. Rebar, welded wire mesh or fiber, and the choice matters less than the placement. Steel does nothing sitting on the ground. It has to be supported on chairs at the specified height within the slab and stay there through the pour. Pulling mesh up with a hook while the concrete goes down is a technique that exists and it does not work reliably. Walk the pad before the pour and look at whether the steel is supported.
Joints. Concrete shrinks as it cures and it will crack. Control joints decide where. Sawcuts have to be made within a specific window after the pour, deep enough to create a real plane of weakness, and laid out in panels that avoid long thin rectangles and re-entrant corners. Late sawcutting is a common cause of random cracking that gets blamed on soil, and shallow sawcutting simply does not control anything.
Curing. This is where the desert punishes shortcuts. High temperature, low humidity and wind together drive surface evaporation faster than bleed water can reach the top, and the result is plastic shrinkage cracking that appears within hours of placement. The countermeasures are known: schedule the pour for the cooler part of the day, use windbreaks, apply an evaporation retarder, and cure properly with a curing compound or wet cure. Summer pours in Las Vegas and Phoenix demand this attention. Winter pours are easier and are one reason scheduling matters.
Finish. The finish has to suit what goes on top. A hard steel-troweled surface is dense and slick, and acrylic coatings do not bond to it well without preparation. Court slabs are typically finished to a texture appropriate for coating, and the surface is then prepped and profiled before the system goes down.
Where the surface system fits
The surface is a wear layer and a playing characteristic, not a structural component. Acrylic systems bond to the slab and take on its geometry and its cracks. Modular tile spans small imperfections and drains, but tile does not repair a slab that is moving, and a failing base will telegraph through any product on top of it. Our overview of court surface options and the detail on court flooring tiles cover those choices.
Concrete needs to cure before it gets coated. Coating too early traps moisture and produces blistering and delamination that is not the coating manufacturer’s fault. Where moisture is a question, a moisture test before surfacing is cheap insurance.
How to tell whether it was done right
You mostly cannot, after the fact. So ask before.
Ask for the base section: subgrade preparation, base material and thickness, slab thickness, reinforcement type and placement, and joint layout. Ask whether compaction will be tested and by whom. Ask for concrete delivery tickets and the mix design. Ask what the curing method will be and what the plan is if the pour lands on a very hot day. Ask to see the joint layout drawing before the pour rather than after.
A builder who does this work properly will answer those questions immediately, because they already made those decisions. A builder who gets vague is telling you something useful.
What base failure actually looks like
Random cracking that does not follow the joint pattern. Cracks that open and close with the seasons. Panels that have moved relative to each other so one edge sits proud of the next. Depressions that hold water where none existed at handoff. Coating that fails repeatedly in the same location after being repaired.
Those symptoms are structural, and resurfacing does not fix any of them. It covers them for a season or two. The full diagnostic breakdown lives in why sport courts crack, and the decision framework for what to do about it is in resurface versus replace.
We build to the section, not to the bid, on every new court construction project in Nevada and Arizona.
Frequently asked questions
How thick should a sport court slab be?
There is no universal thickness. It is a design decision based on subgrade strength, aggregate base thickness, soil behavior, reinforcement and expected use. A builder should tell you the specified thickness for your project and why. Be skeptical of anyone who quotes a number before asking about your soil.
What is the base under a sport court made of?
Typically a graded crushed aggregate placed and compacted over a prepared subgrade, often with a geotextile separation fabric between the two. The gradation matters as much as the depth, since well graded material locks together under compaction while uniform or fines-heavy material does not.
Can a good surface make up for a bad base?
No. Acrylic coatings take on the geometry of the slab, and while modular tile spans minor irregularities, neither product stops a moving slab. A base problem shows through whatever is installed above it, usually within a few seasons.
Why do courts crack when the concrete is new?
Cracking within hours or days of placement is usually plastic shrinkage caused by rapid surface evaporation, which desert heat, low humidity and wind all accelerate. It is controlled through pour timing, windbreaks, evaporation retarders and proper curing. Cracking that appears later and ignores the joint pattern generally points to subgrade or base problems.
Do I need a soils report for a backyard court?
Not on most residential projects. It becomes worth the cost on sites with expansive clay, deep or uncontrolled fill, prior settlement in nearby structures, or unusual grading. If the house has a foundation history, get the report.
If you want the section specified in writing before you sign anything, call Nevada at (702) 883-8386 or Arizona at (480) 878-2292, or request a project quote.









