Drain cell calculator — podium and terrace build-up
Tell us the area, what goes on top and how deep the soil is. The calculator picks RDC-20 or RDC-30 and counts the panels, the filter geotextile and the growing medium.
Free access for engineers and buyers
Sign in with a one-time code: no password to remember. All ten Retech calculators then open on this device, and your details reach the Retech desk so an engineer can help with your project. We do not share them.
Results appear here as you type.
How the calculation works
RDC-30 is chosen when vehicles drive over the podium or the soil is deeper than 600 mm; otherwise RDC-20. Panels are 500 × 250 mm, 8 to the m², plus 5% for cutting. The filter geotextile, RNW 150 GSM, covers the area with 10% laps and turns up the edges to finished soil level (soil depth + 100 mm). Growing medium is area × depth, ordered 15% over for settlement; saturated soil weighs about 1.8 t/m³. Example: a 40 × 20 m podium that people walk on, with 300 mm of soil, needs RDC-20: 6,720 panels, about 930 m² of geotextile (2 rolls) and 276 m³ of soil to order.
Planning quantities for budgeting and enquiry. A Retech engineer confirms the grade and quantity against your drawings before order.