Who this guide is for
- Owners trying to understand what sits under a court
- Clubs planning durable courts on varied ground
- Facility planners scoping site investigation
- Anyone preparing questions about ground and base work
Why the sub-base matters
The sub-base carries everything above it and connects the court to the ground. If the ground is soft, variable or poorly drained, the sub-base design has to respond, because problems beneath the base tend to surface as cracking, movement or pooling later. Getting it right is foundational to a court that lasts.
Because the sub-base is hidden once the court is built, it is easy to underspend or overlook. Treating it as a serious planning topic, informed by ground investigation, helps avoid costly problems down the line.
- Spreads loads from the court into the ground
- Helps water move away from the base
- Responds to the site's specific ground conditions
- Hidden once built, so easy to underestimate
Ground conditions and investigation
Ground conditions vary across sites and even across a single plot. A site assessment, and where needed a ground investigation, informs how the sub-base should be designed. Slopes, fill, soft spots and water all influence the approach.
This is why feasibility and site assessment come before detailed base design. A qualified professional can advise what investigation your site needs and how the findings shape the sub-base.
Drainage within the build-up
Drainage is not only a perimeter concern; how water moves through and beneath the build-up matters too. The sub-base often plays a role in helping water clear, and this is planned together with the base and the wider drainage strategy.
Because these elements interact, sub-base, base and drainage are best reviewed as a system by qualified professionals rather than decided separately.
Why the sub-base is a quality and value decision
Because the sub-base is invisible once built, it is tempting to treat it as a place to economise. Yet problems that originate beneath the base are among the hardest and costliest to fix later, so investing attention here protects the whole project.
Treat the sub-base as a core quality decision informed by ground investigation, not a line to trim. A qualified professional can explain what your site needs and why it matters.
Sub-base planning checklist
- 1Have you arranged a site assessment of the ground conditions?
- 2Have you discussed whether ground investigation is needed?
- 3Have you reviewed how the sub-base handles your site's drainage?
- 4Have you matched the sub-base approach to the base and surface?
- 5Have you considered slopes, fill or soft spots on the site?
- 6Have you left layer and compaction details to qualified engineers?
- 7Have you confirmed official dimensions and standards with a supplier or federation?
- 8Have you planned for the sub-base as a serious cost and quality item?
Common mistakes to avoid
- Underspending on the sub-base because it is hidden
- Skipping site assessment or ground investigation
- Ignoring how water moves beneath the base
- Assuming one sub-base approach suits every site
- Deciding the sub-base separately from base and drainage
- Skipping confirmation of official dimensions with the supplier
When to involve a professional
- A qualified professional should assess ground conditions and advise on investigation.
- Sub-base design, compaction and layer details are specialist engineering tasks.
- Official court dimensions and standards vary and should be confirmed with the relevant federation, supplier or designer.
- Sub-base, base and drainage should be reviewed together by qualified professionals.
Frequently asked questions
Questions readers ask about this topic
What is a sub-base and why does it matter?
The sub-base is the prepared layer between the ground and the court base. It spreads loads and helps water move. Problems beneath the base often surface later as cracking or pooling, so the sub-base is a key planning item that qualified professionals should design.
Do I need a ground investigation?
It depends on the site. Variable, soft or sloping ground may warrant investigation. A site assessment by a qualified professional can advise what your site needs before the sub-base is designed.
Can a good surface make up for a poor sub-base?
No. A surface reflects what sits beneath it. If the sub-base or base is inadequate, problems tend to show through. The build-up should be designed as a whole by qualified professionals.
How does the sub-base affect drainage?
The sub-base often helps water clear from beneath the base, working with the wider drainage strategy. Because these interact, they should be planned together by qualified professionals for your site and climate.
Keep reading