Construction of Drainage Boards in Underground Garages

1. Introduction

Drainage boards (also known as drainage mats or composite drainage systems) play a 

critical role in underground garage construction by:

• Preventing water accumulation behind retaining walls

• Reducing hydrostatic pressure on waterproofing membranes

• Providing a clear drainage path to sump pumps

2. Material Selection

High-performance drainage boards should meet:

• Compressive strength: ≥500 kPa (EN 12430)

• Flow capacity: ≥0.5 l/m·s (ASTM D4716)

• Chemical resistance: pH 2-12 compatibility

• Geotextile filter layer: 110-150 g/m² nonwoven (to prevent clogging)

3. Installation Procedure

3.1 Substrate Preparation

• Verify structural slab is properly sloped (1-2% gradient)

• Remove sharp protrusions (>3mm) that could damage membranes

• Clean surface of debris and standing water

3.2 Board Installation

1. First layer: Install waterproofing membrane (tested to 0.5MPa water pressure)

2. Drainage board orientation:

• Dimpled side against waterproofing

• Flow channels aligned with fall direction

3. Seaming:

• Overlap minimum 100mm at edges

• Mechanically fastened every 300mm

4. Perimeter details:

• Connect to perimeter drain pipes via sock-wrapped connectors

• Seal penetrations with bentonite tape

3.3 Protection Layer

• Install 400g/m² geotextile separation layer

• Pour structural slab (minimum C25/30 concrete)

4. Quality Control

5. Benefits of Proper Installation

✔ 30-year design life when combined with quality waterproofing
✔ 60% faster water removal vs. granular drainage layers
✔ Space savings: 50mm board replaces 300mm gravel layer

6. Common Mistakes to Avoid

✖ Installing boards upside-down (dimples must face membrane)
✖ Inadequate slope toward drainage points
✖ Failure to protect boards during rebar placement

Technical Support Available
Our engineering team provides:
→ Site-specific drainage calculations
→ CAD details for critical junctions
→ Third-party inspection services

"Dry garages start with proper drainage"

Keywords: Garage drainage system, Hydrostatic pressure relief, Dimpled membrane, 

Below-grade waterproofing

(This specification aligns with EN 13948 and ACI 302.1R-15 standards)

Would you like to include:

1. Material comparison table (HDPE vs. PP boards)

2. Construction sequence animations

3. Cost analysis vs. traditional methods?