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Component Design CIRIA C753 §20

Permeable Paving Calculator

CIRIA C753 §20: permeable pavement sizing for storage, treatment and infiltration.

Site Params

Pavement

Storage

Results

Step 1: Site Parameters & Rainfall

Project Information

Project Name

Site Reference

Engineer Name

Date

Fields marked * are required

Project Reference

Site Name

UK Postcode (for SAAR) ?

📍 UK overview map for site context

Rainfall Data Method

Return Period ? *

Storm Duration (min) *

Climate Change Epoch * Climate Change Band * Climate Change Allowance (%) *

Source: EA May 2022 peak-rainfall allowances (per management catchment; national-median reference). Auto-set from the epoch + band + design return period via SV.getEACC; overridden by your catchment selection below. Editable.

Management catchment (EA allowance auto-fill) EA allowance for this catchment (%) ?

Selecting your catchment auto-fills the exact EA allowance (EA May 2022 dataset, 90 catchments); editable. Guidance: pick the epoch spanning the design life (2070s for a ~100-year lifetime); upper-end (95th) band for essential/vulnerable development or where the LPA requires, central (50th) otherwise. Cross-check on the EA peak rainfall map.

SAAR (mm/year) ? *

Regulatory Compliance Inputs

Total Site Area (ha) ?

Greenfield QBAR Rate (l/s) ?

Land Use Pollution Hazard ?

Contributing Catchment

Total Catchment Area 0.00

Weighted Runoff Coefficient (C) 0.00

Effective Area (C × A) 0.00

Step 2: Pavement Design

Paving Type ?

Permeable Paving Area (m²) ? *

Jointing Material ?

Sub-Base Design

Traffic Category ? *

Sub-Base Type ? *

Sub-Base Depth (mm) ? *

Design Life Clogging Factor ? *

Geotextile Membrane

Soil Infiltration Rate (m/hr) ? *

Groundwater Level (m below surface) ?

Groundwater Clearance Below Sub-Base (m) ? *

Step 3: Storage & Outflow Design

Void Ratio (n) ? *

Available Storage Volume

Sub-Base Area (m²)

100.00

Sub-Base Depth (m)

0.15

Available Storage (m³)

5.25

Outflow Design

Outflow Mode ? *

Infiltration Safety Factor ? *

Overall Safety Factor ? *

Step 4: Design Results

Complete the design steps above to view results.