The Foundation of a Long-Lasting Basketball Court
A basketball court is only as good as the surface beneath it. Long before tiles are clipped together or a hoop is installed, the sub-base determines how the court will perform, how long it will last and whether problems appear months or years down the line.
This guide focuses specifically on building the sub-base for a basketball court. It does not cover surface installation or hoop assembly — those steps come later. Getting the foundation right is what allows everything else to work properly.
What Is a Basketball Court Sub-Base?
The sub-base is the engineered foundation that supports the playing surface. Its job is deceptively simple: stay flat, stay stable and manage water. In practice, this means carrying player loads, resisting ground movement and preventing moisture from damaging the court above.
For basketball courts, particularly those using modular flooring, the sub-base must be flatter and more precise than a typical patio, driveway or garden slab. Small deviations that would be acceptable elsewhere can cause problems on a court.
Choosing the Right Type of Sub-Base
Most basketball courts are built on either concrete or asphalt, with concrete being the preferred solution in the majority of installations. It provides a stable, predictable foundation that supports consistent ball bounce and long-term surface performance.
For basketball courts, a reinforced concrete slab should typically meet the following criteria:
- Minimum thickness of 100–150 mm
- Steel mesh or rebar reinforcement
- Laser-levelled finish
- Subtle fall for outdoor drainage
Asphalt bases can be suitable in certain situations, but they require stricter preparation and are more prone to long-term movement.
Flatness and Tolerance Requirements
A basketball court surface is unforgiving when it comes to uneven foundations. Unlike paving or general hardscaping, the playing surface amplifies imperfections rather than hiding them. Even minor deviations in the sub-base can affect ball bounce, create uncomfortable footing and make surface installation more difficult.
For this reason, basketball courts require a higher standard of flatness than most exterior slabs. The aim is not visual perfection, but consistent performance across the entire playing area. As a practical guide, a basketball court sub-base should meet the following tolerance expectations:
- No more than 3–5 mm deviation over 3 metres
- No abrupt level changes or ridges
- No standing water after rainfall (for outdoor courts)
Meeting these tolerances at the sub-base stage prevents issues that are difficult or impossible to correct once the court surface is installed.
Drainage and Ground Preparation
For outdoor courts, drainage is as important as flatness. Water that cannot escape will eventually cause movement, cracking or frost damage.
Good ground preparation typically involves a compacted stone or hardcore layer beneath the slab, combined with a gentle fall to guide water away from the court area. The goal is not to create a visible slope, but to prevent standing water from forming anywhere on the surface.
Ignoring drainage rarely causes immediate failure — it causes slow, expensive problems later.
Sub-Base Readiness Check
Before you move on to installing your basketball court surface, pause and confirm the following. If you can confidently tick every box, your sub-base is ready.
Your sub-base should be:
- Structurally sound, fully cured and free from cracks
- Flat within basketball court tolerances (no visible dips or ridges)
- Dry, clean and clear of debris
- Properly drained, with no standing water after rainfall
- Built to the correct dimensions and orientation for your court layout
If any of these points are uncertain, resolve them before installing the surface. Fixing issues at this stage is straightforward. Fixing them later is not.
OnCourt provides technical drawings and tolerance guidance for contractors building court sub-bases.
Common Mistakes to Avoid
Most sub-base issues stem from shortcuts rather than bad intentions. Using patio-grade tolerances, skipping reinforcement, pouring without accurate level control or rushing the curing process are all mistakes that compromise the court before it’s even built.
- Using poor tolerances
- No reinforcement
- Pouring without level control
- Installing before full cure
The key principle is simple: fixing sub-base problems after installation is far harder than building it correctly in the first place.
When Is the Sub-Base Ready?
Before moving on to surface installation, the sub-base should be fully cured, clean and structurally sound. It must meet flatness tolerances and show no signs of cracking, movement or soft spots.
Once these conditions are met, installing the court surface and hoop becomes straightforward.
Who Should Build the Sub-Base?
While many basketball court surfaces can be installed DIY, sub-base construction is best handled by experienced groundworks professionals. This stage requires the right equipment, knowledge of local ground conditions and an understanding of tolerance requirements that go beyond general landscaping work.
OnCourt provides technical drawings and specifications so local contractors can build the base correctly without guesswork. This approach combines local expertise with clear performance standards.
FAQ sur la sous-base des terrains de basket-ball
La sous-base est la couche de fondation compactée située sous la surface de votre terrain. Elle soutient le système de dalles modulaires, absorbe la charge, empêche les mouvements et garantit un rebond cohérent du ballon. Sans une sous-base solide, le terrain peut se déplacer, présenter des zones mortes ou avoir un mauvais drainage avec le temps.
La profondeur d’excavation dépend du type de sol, des conditions du terrain et du climat, mais se situe généralement entre 100 mm et 250 mm. Pour les sols meubles ou les climats froids, il peut être nécessaire de creuser plus profondément pour éviter le soulèvement dû au gel et les affaissements.
Une sous-base standard comprend :
– Du gravier concassé de type 1 MOT pour le compactage et le drainage.
– Une couche de sable grossier compacté ou de fine couche de finition.
– Facultativement, un géotextile pour contrôler les mauvaises herbes et stabiliser le sol.
Pour des résultats optimaux, terminez avec une dalle en béton ou en asphalte bien nivelée pour l’installation de dalles sportives modulaires. Comme indiqué dans cet article, une tolérance de planéité de 5 mm sur un rayon de 3 m garantit des performances optimales.
Votre sous-base doit être plane à moins de 5 mm de variation sur un rayon de 3 m. Cette tolérance est essentielle pour que vos dalles modulaires s’emboîtent correctement et garantissent une expérience de jeu sûre et homogène.
Oui. Un bon drainage est essentiel pour éviter la stagnation de l’eau sous la surface du terrain modulaire. Prévoyez une légère pente, des couches de base perméables ou des caniveaux si nécessaire pour les terrains extérieurs.
Oui, si vous êtes à l’aise avec l’excavation et le compactage. De nombreux bricoleurs réalisent eux-mêmes leur sous-base, mais pour des terrains plus grands ou complexes, nous recommandons de faire appel à un entrepreneur professionnel.
Faire appel à un professionnel local du terrassement est souvent le meilleur choix. Il saura évaluer les conditions du sol, anticiper les problèmes de drainage spécifiques à la région, et mobiliser efficacement les bons équipements et matériaux. Une sous-base préparée professionnellement vous assure aussi que votre terrain offrira des performances optimales pendant des années.
L’installation du panier Mega Slam à sceller au sol se fait en deux étapes. Il faut d’abord creuser un trou de 1,25 m de profondeur pour couler un socle en béton qui supportera le système. Ensuite, il faut monter le panier. Les systèmes Mega Slam sont lourds – c’est ce qui les rend si robustes pour un usage domestique. Prévoyez de l’aide pour le levage et l’assemblage. En savoir plus sur Installation de Mega Slam Hoops.
NOTE - Les ancrages du panier et des composants doivent être installés pendant la construction de la sous-base. Configurez et commandez votre terrain, panier et accessoires à l’avance pour que les ancrages soient prêts à être posés pendant cette étape.
Next Steps
With the sub-base complete, you’re ready to move from groundworks to court assembly.
English (UK) 
Български 
Čeština 
Dansk 
Deutsch 
Nederlands 
Español 
Eesti 
Français 
Ελληνικά 
Hrvatski 
Magyar 
Italiano 
Latviešu valoda 
Lietuvių kalba 
Norsk bokmål 
Português 
Polski 
Română 
Српски језик 
Slovenčina 
Slovenščina 
Suomi 
Svenska 
Türkçe 
العربية