Do I need a drain system under turf?

When you do and do not need under-turf drainage

The goal is simple: move water away fast so the surface stays usable and clean. Whether you need added drainage depends on soil, slope, surface below, and water volume.

You likely need added drainage if

• Native soil is slow draining clay or compacted fill that puddles after rain.
• Installing over concrete, asphalt, pavers, or a roof deck with minimal slope.
• The area sees heavy hose-downs or frequent pet use that adds lots of water.
• Runoff concentrates from downspouts, neighboring grades, or hillside catchment.
• You want a shock pad or panel system and need to maintain flow paths under it.

You likely do not need added drainage if

• Soil is sandy or loamy and already drains well.
• You build a compacted, permeable stone base and maintain at least a slight surface fall to an outlet.
• There are no concentrated water sources and rainfall is typical for your region.

How to evaluate your site fast

1. Quick soil check

• Dig a small hole about 8 to 12 inches deep. Fill with water and let it drain once to pre-wet. Refill. If water is gone within a few hours, your soil is generally cooperative. If it lingers overnight, plan for added drainage.

2. Confirm slope and an outlet

• Target a visible fall away from structures. Even a slight slope helps. Make sure water has somewhere legal and safe to go, like a swale, drain inlet, or daylight.

3. Map water sources

• Note downspouts, uphill grades, or areas you plan to wash frequently. Concentrated inputs often justify panels or a French drain.

Proven build-ups that drain

Standard permeable base on natural ground

• Excavate organic material to stable subgrade.
• Place 3 to 6 inches of angular, compactable stone appropriate for your region. Avoid soil-heavy or muddy blends that seal up.
• Add a 0.5 to 1 inch leveling layer if needed. Compact in thin lifts to a firm, even surface that still allows water to pass.
• Keep a slight surface fall toward your intended outlet.

This approach works well on free-draining soils and is the most common turf base.

Over concrete, asphalt, pavers, or roofs

• Use a purpose-built drainage mat or panel between the hard surface and turf.
• Confirm the hard surface has positive slope to weep points or drains.
• Keep weeps and scuppers clear. Do not block them with adhesive or edge mortar.

Panels create flow channels so water cannot sit against the turf backing. On roofs and patios, they are essential for consistent performance.

Wet clay sites or low areas

• Combine a permeable stone base with a French drain at the low edge or centerline, daylighted or tied into a legal storm outlet.
• Consider a drainage panel layer above the base in the worst spots to speed lateral movement.

Drainage panels and French drains in plain English

• Drainage panels or mats: Slightly raised, high-flow pathways under the turf that move water laterally to edges or drains. Ideal over slabs and in high-load water zones.
• French drain: A perforated pipe wrapped in clean stone and fabric that collects water and discharges it to a safe outlet. Ideal for low points or clay-heavy yards.

Both solutions protect the surface from puddling and help control odor in pet areas by moving rinse water away quickly.

Installation checklist that keeps water moving

• Keep a consistent surface fall and do not create birdbaths.
• Use clean, angular stone and compact in shallow lifts. Soft or muddy bases trap water.
• Use separation fabric under the base where soils are silty or expansive to prevent migration.
• Choose infill that supports drainage and your use case. Rinseable infills pair well with pet areas.
• Plan edge restraints that do not dam water. Leave weep gaps where needed.
• If using a pad, select a perforated or grooved product that maintains flow to edges.
• Hose test before final infill. Watch where water goes and adjust while it is easy.

Maintenance and troubleshooting

Routine care

• Blow or brush debris off the surface. Debris can clog flow paths.
• Rinse pet areas regularly and reapply enzyme cleaners as needed.

Signs you need more drainage

• Puddles that persist well after rain stops.
• Persistent odor in pet zones despite routine cleaning.
• Soft or spongy spots that do not firm up after drying.

Fixes

• Open weep gaps, lower a small edge section, or add a discreet trench drain where water collects.
• Retrofit a French drain at the low edge and tie to an approved outlet.
• In extreme cases on slabs, add or upgrade drainage panels.

Costs and planning

• A standard permeable base is the most economical and works on most well-draining soils.
• Adding drainage panels or a French drain increases materials and labor. Expect a noticeable uplift that reflects site complexity and access.
• Right-sizing drainage from the start is cheaper than a tear-out later.

When to bring in a pro

• Rooftops, over occupied spaces, or anywhere waterproofing is involved.
• Large catchment areas or complex grading.
• Local codes or HOA rules that govern stormwater discharge.

Get it graded, get it flowing, and your turf will play clean and fast. If you want a second set of eyes, FusionTurf can help you spec the right build for your site.